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GRADE 8: G8SHSCIA INTEGRATED SCIENCE SY 2023-2024 Title PHYSICS No. of hours 36 hours Quarter FIRST Coverage August to October Prepared By ROMALYN D. PARADO Schedule 4 hours/week I. Introduction Grade 8 Science module is a part of the spiraling curriculum prepared by the Department of Educat...

GRADE 8: G8SHSCIA INTEGRATED SCIENCE SY 2023-2024 Title PHYSICS No. of hours 36 hours Quarter FIRST Coverage August to October Prepared By ROMALYN D. PARADO Schedule 4 hours/week I. Introduction Grade 8 Science module is a part of the spiraling curriculum prepared by the Department of Education. The first quarter covers the Physics aspect of the science curriculum which focuses on the factors that affect motion of an object based on the Laws of Motion and Energy. As a Grade 8 student, you will learn about the concept of force and its relationship to motion. You will also use Newton's Law of Motion to explain why objects move or not move. Hopefully, you will realize that if force is applied on a body, work can be done and may cause a change in the energy of the body. You will also realize that transferred energy may cause changes in the properties of the objects. These changes are observable in temperature, amount of current, speed of sound and colors of light or intensity. When you start learning the module, you will see that it is divided into submodules to be accomplished weekly focusing to answer the essential questions given below: How do forces affect the motion of an object? How are work and energy related? How does heat affect matter? What are the factors that affect the speed of sound? What properties of light explain the separation of colors in white light? What are the factors that affect the current in a circuit? II\. Lesson Coverage Week Lesson/ Topic Title Learning Targets At the end of the lesson, the learner will be able to Expected Output Week 1 Lesson 1: Laws of Motion relate force, motion, mass and inertia state and explain Newton's laws of motion explain how force and mass are related to acceleration. solve word problems using the second law of motion using real life situations. Pre-Assessment Formative Assessment 1 Summative Assessment 1 Mini Task 1: Motion Game Week 2-3 Lesson 2: Work, Power, and Energy formulate a scientific definition of work. identify situations in which work is done and which no work is done. describe how work is related to power and energy differentiate potential and kinetic energy. relate speed and position of object to the amount of energy possessed by a body. Formative Assessments 2-5 Summative Assessment 2 rdp2023 \| G8SHSCIA 8 Week 4-5 Lesson 4: Sound and Light describe sound. explain why sound travels faster in solid. explain the equation for wave velocity. describe what makes up white light. define refraction. explain what happens to light when it travels through the atmosphere. explain the scattering of light. Formative Assessment 6 Summative Assessment 3 Week 6 Lesson 5: Heat explain what combustion is. define heat. distinguish heat and thermal energy explain the effects of excessive heat in the human body and in the environment. Formative Assessment 7 Week 7 Lesson 5: Electricity describe how an electric current flow through a wire. differentiate a conductor, insulator and semiconductor. explain why electricity flow differently through different materials. explain the relationship of current, voltage and resistance. describe a series and parallel circuits and enumerate the advantage of one over the other. enumerate safety measures in using electricity. Formative Assessment 8 Summative Assessment 4 Week 8 Examination Week Week 9 Performance Task Week Content Standard: The learner demonstrates understanding of 1\. Newton's three laws of motion; 2\. work using constant force, power, gravitational potential energy, kinetic energy, and elastic potential energy; 3\. the propagation of sound through solid, liquid, and gas; 4\. some properties and characteristics of visible light; 5\. heat and temperature, and the effects of heat on the body; and 6\. current- voltage-resistance relationship, electric power, electric energy, and home circuitry. PT: NEWTON'S OLYMPICS Performance Standard: The learner is able to 1\. develop a written plan and implement a "Newton's Olympics"; and 2\. discuss phenomena such as blue sky, rainbow, and red sunset using the concept of wavelength and frequency of visible light. III\. Study Guide Success is, of course, determined in many ways, and I hope you think of it not just in terms of reaching the end of your modules, but also in how much you enjoyed the act of studying. This module is set out in a way to help you prepare for study, set goals, stay motivated, and ultimately enjoy the process of learning. I hope that you get the most out of your module and that it leads you up to your greatest dreams and beyond. There are several ways to help you stay motivated during your studies. These are essential tools that can kick-start your motivation if it starts to lag. rdp2023 \| G8SHSCIA 9 1\. Revisit your goals. Having a clear purpose for studying will feed your determination to complete your module. To remind yourself of what that purpose is, revisit the goals you established before you start to study. 2\. Create a schedule you can stick to. The importance of scheduling is essential to help keep you on track and motivated too. The more you study, the more it becomes a habit. 3\. Make studying a habit. It is essential to find a way of making room for it within your routine. Defining a routine time for your study will make it easier for you to clear your head and be focused from the time you open your first page. 4\. Reward yourself. You may reach an impasse in your module where you're just not interested anymore. This is when prompting yourself to continue studying with the promise of a reward can have a positive effect. The truth is that within these promises, you're actually teaching yourself self- discipline, and this is probably one of the most essential skills you could ever have as a self-study learner. 5\. Stay healthy. Maintaining a healthy lifestyle while you study is necessary for keeping your energy balanced, and your mind motivated. You need a healthy body and mind to tackle your schoolwork with continual enthusiasm and effectiveness. 6\. Balance your time between studying and your social activities. You must give your module enough attention to enable you to complete it successfully. Make sure that your studies become part of your everyday routine, and do not take over your daily life. Locking yourself away to concentrate solely on your module will only drain you mentally and emotionally after a while, so make sure you stay in touch with friends and family. They'll probably want to know how you're getting on with your studies anyway. 7\. Meditation. Meditation isn't just for Buddhist monks and yoga gurus. Even five minutes of deep breathing and focused thinking can help center your mind in preparation for studying. An effortless meditation practice which you can do anywhere as follows: a\. Close your eyes and focus on your breath. b\. Take a few slow, deep breaths in through your nose and out through your mouth. c\. Tell yourself that you will now release all the negative noise and mindless chatter with each exhalation of your breath. As you breathe in, focus on 'being' rather than on 'thinking nothing.' d\. However, if your thoughts enter your mind, gently acknowledge them and let them go. Refocus on the present moment. e\. Do this for at least 5 minutes, before opening your eyes and returning to your studies more relaxed and refreshed. LEARNER ASSESSMENT GUIDANCE I want to help you get the most of your course assessments, and please take a moment to read through the information to ensure that you understand the marking process. Please do not copy directly from the materials, as this may result in a loss of marks. Where possible, you must demonstrate your understanding and interpretation of the module content to your teacher. In some questions, you may be required to provide definitions/processes/procedures in the exact format as part of an answer. Multiple choice questions -- choose enough answers to cover the marks awarded. Free text questions - one mark for each point, explanation, or example given. The number of marks indicates the number of points required and/or the level of depth required in the answer. Word count on essays -- 10% leeway of the word count given. If an essay is under the 10% leeway, marks will be deducted. Anything extra over the word count is fine. Uploading a file -- I will not accept an already completed diagram sourced from the internet or any other external sources. All assessments are in the google classroom. If you are not able to answer online, please contact your teacher as early as possible. Answers to formative assessments are released as soon as you can accomplish the task, some at the end, others per item. As for summative assessment results, you will be notified as soon as it is ready. PLAGIARISM: Copying from Internet Sources and Referencing and Citing Sources Questions You may include information from the course materials online, but you must include where the information came from (e.g. the web link) and also include your own words to show you have a full rdp2023 \| G8SHSCIA 10 understanding. If a question is purely research-based, all references must be included. You may use the Comprehensive Guide to APA Citations and Format available at https://www.citationmachine.net/apa/cite-a-book. If an answer is copied directly from an online source or course materials with either no reference or without including your own words to show understanding, marks will be deducted. Once you have answered a question in the assessment, please make sure you press the 'Submit' button (if applicable) to ensure that your answers get saved if you need to refer back to your notes. When you get to the end of the module assessment questions, please press the 'turn in' button so that your answers are sent for marking. You can keep track of your progress and check your module marks by clicking your google classroom, 'classwork tab', 'view your work' at the top. These tabs will help you keep track of where you are up to. IV\. Pre-Assessment Let's find out how much you already know about this module. Read and understand each item carefully then choose the letter of your answer. Answers will be revealed after taking the short test. Take note of the items that you were not able to answer correctly and look for the right answer as you go through the module. FIRST QUARTER PRE-ASSESSMENT: 1\. Which of the following equations represents Newton's second law of motion? A. a=Fm B. a=F C. F=ma D. m=aF 2\. What is the SI unit for force? A. J B. Kg C. m/s D. N 3\. Which of Newton's laws best explains why motorists should buckle -- up? A. First law B. Second law C. Third law D. Law of Gravitation 4\. Which object has more inertia? A. a basketball B. a bowling ball C. a pingpong ball D. a volleyball 5\. What kind of friction is present when objects are not moving? A. Fluid friction B. Rolling friction C. Sliding friction D. Static friction rdp2023 \| G8SHSCIA 11 6\. Which of the following quantities are related to work? A. force and acceleration B. force and displacement C. mass and acceleration D. mass and displacement 7\. How do we call the rate at which work is done? A. Energy B. Force C. Power D. Inertia 8\. Which of the following scenarios show that NO work is done? A. hitting a baseball B. holding a heavy box C. pushing a cart D. walking downstairs 9\. How do we call the energy possessed by a body due to its position? A. chemical energy B. heat energy C. kinetic energy D. potential energy 10\. An arrow that is pulled back by a bow has which type of energy? A. Chemical Potential Energy B. Elastic Potential Energy C. Gravitational Potential Energy D. Kinetic Energy 11\. The spreading of colors by a prism is called A. diffraction B. dispersion C. reflection D. refraction 12\. At which temperature will sound travel fastest? A. 10 oC B. 40 oC C. 60 oC D. 80 oC 13\. When an object is heated, its molecules \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ A. become larger in size B. do not change in position C. move faster and farther apart D. move slower and closer together 14\. Which of the following is a poor conductor of electricity? A. cloth B. copper C. rubber D. water rdp2023 \| G8SHSCIA 12 15\. Which of the following is TRUE in a parallel circuit? A. Voltage is constant. B. Current is constant. C. The total resistance and voltage is constant. D. The total resistance is equal to the sum of the individual resistances. rdp2023 \| G8SHSCIA 13 V. Lesson Proper LESSON 1 LAWS OF MOTION Objectives: In this lesson, you are expected to: 1\. relate force, motion, mass and inertia; 2\. state and explain Newton's laws of motion; 3\. explain how force and mass are related to acceleration; 4\. solve word problems using the second law of motion using real life situations. INTRODUCTION (Explore) Let's start this module by gathering your thoughts about the topics that we will be covering in this quarter. The activities will give you a background on what to learn for this quarter. ACTIVITY 1.1 Anticipation-Reaction Guide Instructions: The statements below are situations that involve the concepts of Newton's Law of Motion, work and energy, heat and temperature, sound, light, and electricity. On the first column titled, "Before," put a check mark if you agree with the statement and put an "X" mark if otherwise. Do not answer the "After" Column statements yet. Before Statements After You can remove the tablecloth underneath a set of tableware without toppling them off. A sudden stop of the vehicle you are riding may cause you to be thrown backwards. It is faster and easier to move an empty grocery cart than the one loaded. You are doing work when you push against a wall. A rolling bowling ball transfers its energy to the bowling pins once it hit them. During a cold day, your body temperature is maintained because your body releases more heat in order to do this. Lightning strikes first before thunder happens. When the current in the circuit exceeds the wire's current rating, short circuit happens. INTERACTION (Firm-up & Deepen) What is force? How is it related to motion? Force may be defined as a push or pull by one body to another. There are two or more forces that may act on an object at the same time. First are balanced forces - forces that are equal and acting on an object in opposite directions. Since we are talking about opposite directions, then these forces have an algebraic sum of zero; thus they do not cause any change in motion of an object. In a different case, one of the two forces is greater than the other, the rdp2023 \| G8SHSCIA 14 object will move in the direction of the greater force. The algebraic sum of these forces is not equal to zero; thus it will cause a change in the motion of the object. These forces are called unbalanced forces. An unbalanced force will cause an object to start moving, change speed, stop moving, or change direction. Law of Inertia. This law states that every object continues to remain at rest or in uniform motion in a straight line unless a force acts on it to change its state. Inertia is the tendency of an object to maintain its initial state of motion. Newton related the concept of inertia to mass. Mass is a measure of inertia. From this idea, it can be said that an object which is more massive has more inertia or has more resistance to change in motion than a less massive object does. For example, a truck has more inertia than a bicycle. The following may be observed due to inertia: A passenger tends to move forward when the car he or she is on suddenly stops. A bullet fired from a gun continues its motion if not for the resistance of air and the pull of gravity. A moving car remains in uniform motion and is retarded by the force applied on the brakes. Newton's first law of motion has many applications in everyday life. Take for example, seat belts that provide safety to passengers or drivers from injury during accidents. This safety gear provides an unbalanced force that keeps the passenger from a state of motion to a state of rest when the car suddenly stops. Law of Acceleration. This law states that the acceleration of an object is directly proportional to the net external force acting on the object and inversely proportional to the mass of the object. In symbols, a = F m a = acceleration F = force m = mass This equation says that if the force is doubled, the acceleration is also doubled since force and acceleration are directly proportional. On the other hand, acceleration is inversely proportional to mass. This means that an increase in mass will produce a corresponding decrease in acceleration. The structural design of cars is based on Newton's second law. Race cars are designed such that their mass is reduced which, by Newton's second law, is directly proportional to the net force but inversely proportional to the acceleration of the car. If mass is expressed in kilogram (kg) and acceleration is in meter per second (m/s2 ), the unit of force is kilogram.meter per second squared (kg.m/s2 ) or Newton (N). F (newton, N) = m (kg) x a (m/s2 ) 1 N = 1 kg.m/s2 Is mass the same as weight? Mass and weight are often used interchangeably. In physics, mass and weight are two different concepts. Mass is the amount of matter that an object possesses. The weight of an object is the gravitational force that the body experiences. The uniform acceleration caused by the gravitational force is referred to as acceleration due to gravity (g), which is equal to 9.8 m/s2. So your weight is computed by multiplying your mass and acceleration due to gravity. Mathematically it is expressed as W = mg rdp2023 \| G8SHSCIA 15 Where W = weight; m= mass; g = acceleration due to gravity The mass of an object does not change. Weight can change depending on the acceleration due to gravity. Because of acceleration due to gravity, an object on the surface of the moon will only weigh 1/6 of its weight on Earth. Since weight is a force, its SI unit is newton (N). Law of Interaction. This law states that for every action there is an equal and opposite reaction. Newton's third law shows that forces always occur in pairs. When a rocket engine burns its fuel, gases are produced. The gases exert a force on the rocket, to which the rocket reacts with an equal and opposite force. It is the reaction force of the gases on the rocket that drives the rocket forward. Online Activity It is time for you to use the web to establish your understanding about the Newton's Law of Motion. Here are some sites that you need to explore. Be sure to have your notebook and pen ready, so that you can take down notes about the topics presented: 1\. Newton's Law of Motion: http://teachertech.rice.edu/Participants/louviere/Newton/ 2\. First Law of Motion: http://studyjams.scholastic.com/studyjams/jams/science/forces-and-motion/inertia.htm 3\. Second Law of Motion: http://studyjams.scholastic.com/studyjams/jams/science/forces-and-motion/acceleration.htm 4\. Third Law of Motion http://studyjams.scholastic.com/studyjams/jams/science/forces-and-motion/action-and- reaction.htm Process Questions 1\. Do forces always result in motion? 2\. What are the conditions for an object to stay at rest, to keep moving at constant velocity, or to move with increasing velocity? 3\. How is force related to acceleration After doing the web exploration, it is time for you to summarize what you have learned by accomplishing this graphic organizer found in the next activity. rdp2023 \| G8SHSCIA 16 FORMATIVE ASSESSMENT 1: Newton's Three Laws of Motion Graphic Organizer Present the summary of the Newton's Law of Motion by accomplishing this task: INTEGRATION (Transfer) You have completed this lesson. Before you go to the next lesson, you have to answer the post- assessment. SUMMATIVE ASSESSMENT 1 Identification. Identify the law of motion that is illustrated by the following situation. Please write complete answers, ex. Law of Inertia. (10 points) \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 1. A rifle recoils when fired \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 2. A car still moves for a short period even after the brakes have been applied \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 3. A follow- through is needed when a golfer hits the ball with a golf club \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 4. A rocket lifts off from a space-shuttle system \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 5. A cigarette vendor has to move with the bus as he jumps off the bus \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 6. It is easier to push an empty supermarket cart than a full cart. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 7. Walking \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 8. Dribbling a basketball \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 9. Sports cars are designed to be lightweight \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 10. Continued swirling of milk after the stirring is stopped rdp2023 \| G8SHSCIA 17 Constructed Response. Answer the following questions on the spaces provided. Please be guided by the rubric. (15 points) 5 - Answer is very accurate, comprehensive and well-supported; concepts are fully and properly explained; insights presented; 4 - Content is accurate, comprehensive and well-supported; concepts are fully and properly explained; 3 - Appropriate details are included; adequate explanation; 2 - Poor explanation; misinterprets the science concepts; 1 - No analysis of topic; wrong explanation 1\. What is the relationship of mass and inertia? \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 2\. If you increase the force on an object what happens to acceleration? \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 3\. Will your mass change on the moon? Explain. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ rdp2023 \| G8SHSCIA 18 MINI TASK 1 MOTION GAME In the next activity, you need to couple your learned concepts with imagination! Find out how and enjoy your experience. Instructions: Your task is come up with a game/challenge pertaining to any Newton's Laws of Motion using the given set of materials provided. Write the step-by-step procedure on the space provided and explain how the chosen law works in your designed challenge. You can do researches but please avoid copying directly from the internet. Please be guided by our rubric. 10 - Answer is very accurate, comprehensive and well-supported; concepts are fully and properly explained; insights presented; 8 - Content is accurate, comprehensive and well-supported; concepts are fully and properly explained; 6 - Appropriate details are included; adequate explanation; 4 - Poor explanation; misinterprets the science concepts; 2 - No analysis of topic; wrong explanation MATERIALS 2 soft drink bottles 1 100 PHP Bill PROCEDURE \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ JUSTIFICATION \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ MATERIALS Rubber balloon Toy car Adhesive tape PROCEDURE \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ JUSTIFICATION \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ rdp2023 \| G8SHSCIA 19 LESSON 2 WORK, POWER AND ENERGY Objectives: In this lesson, you are expected to: 1\. formulate a scientific definition of work; 2\. identify situations in which work is done and which no work is done; 3\. describe how work is related to power and energy; 4\. differentiate potential and kinetic energy; 5\. relate speed and position of object to the amount of energy possessed by a body. INTRODUCTION (Explore) Let's start this module by gathering your thoughts about one of the topics that we will be covering in this quarter. The activity will give you a background on what to learn for this lesson. We often used the word work to describe something that we do. We say "I have a lot of 'work' to do" or hear our parents say "I must go to 'work'." ACTIVITY 2.1 "Am I working or not?" In the each of the given situation, determine whether work is performed or not. Put a tick (√ ) mark if work was performed and an "X" mark if not. 1\. A news anchor doing his report on television. \_\_\_\_ 2\. A body builder lifting weights from the floor moving it above his head. \_\_\_\_ 3\. A mother pushing her baby trolley on their way to the park. \_\_\_\_ 4\. A waiter carrying a tray. \_\_\_\_ 5\. A student pushing her chair to the other side of the room. \_\_\_\_ 6\. An athlete pushing against the wall. \_\_\_\_ 7\. A child reading a storybook. \_\_\_\_ 8\. A traveler pulling her trolley towards the airport check-in counter. \_\_\_\_ 9\. A guava falling from the tree. \_\_\_\_ 10\. An airplane taking off from the airstrip. \_\_\_\_ INTERACTION (Firm-up & Deepen) Read the materials found in the reading activity to learn about the topics. Do not forget to answer the process questions. Reading Activity The following materials will help you understand about work using constant force, power, gravitational potential energy, kinetic energy, and elastic potential energy. Study them carefully and do not forget to do the activities presented. rdp2023 \| G8SHSCIA 20 Work = Force × Distance Defining Work The teens in the picture on the left are having fun playing basketball. The teens in the picture on the right is working hard studying for an exam. It's obvious who is doing work---or is it? Would it surprise you to learn that the teens who are working are the ones who are having fun playing basketball, while the teens who are studying isn't doing any work at all? The reason why has to do with how work is defined in physics. Work is defined differently in physics than in everyday language. In physics, work means the use of force to move an object. The teens who are playing basketball in the picture above are using force to move their bodies and the basketball, so they are doing work. The teen who is studying isn't moving anything, so she isn't doing work. Not all force that is used to move an object does work. For work to be done, the force must be applied in the same direction that the object moves. If a force is applied in a different direction than the object moves, no work is done. The Figure below illustrates this point. Question: If the box the man is carrying is very heavy, does he do any work as he walks across the room with it? Answer: Regardless of the weight of the box, the man does no work on it as he holds it while walking across the room. However, he does more work when he first lifts a heavier box to chest height. Work is directly related to both the force applied to an object and the distance the object moves. It can be represented by the equation: This equation shows that the greater the force that is used to move an object or the farther the object is moved, the more work that is done. rdp2023 \| G8SHSCIA 21 To see the effects of force and distance on work, compare the weight lifters in the Figure below. The two weight lifters on the left are lifting the same amount of weight, but the one on the bottom is lifting the weight a greater distance. Therefore, this weight lifter is doing more work. The two weight lifters on the bottom right are both lifting the weight the same distance, but the weight lifter on the left is lifting a heavier weight, so she is doing more work. Source: CK-12. (2019, September 04). Work. https://flexbooks.ck12.org/cbook/ck-12-middle-school-physical-science- flexbook-2.0/section/13.1/primary/lesson/work-ms-ps Photo Credits: Playing basketball: https://www.pexels.com/photo/sportsmen-playing-basketball-on-modern-sports-court-3755448/ Studying: https://www.pexels.com/search/studying/ Process Questions 1\. How is work defined in physics? 2\. Write the equation that relates work to force and distance. 3\. Assume that a friend hands you a heavy book to hold as he turns the combination lock on his locker. Which of you does more work? rdp2023 \| G8SHSCIA 22 Given: F = 100 N; d = 200 m Unknown: W Formula: W= Fd Solution: W=(100 N) (200 m) = 20,000 Newton-meter (N.m) Answer: W = 20,000 J Given: F = 100 N; d = 234 m Unknown: W Formula: W= Fd Solution: Work = 100 N × 234 m = 23,400 N m Answer: Work = 23,400 J How Much Work? The equation for work can be used to calculate work if force and distance are known. To use the equation, force is expressed in Newtons (N), and distance is expressed in meters (m). For example, assume that Clarissa uses 100 Newtons of force to push the mower and that she pushes it for a total of 200 meters as she cuts the grass in her grandmother's yard. Then, the amount of work Clarissa does is: Notice that the unit for work in the answer is joule (J). This is the SI unit for work, also equivalent to Newton.meter (N.m). One joule equals the amount of work that is done when 1 N of force moves an object over a distance of 1 m. 1 Joule = 1 N.m = 1 kg.m2 /s2 Question: After Clarissa mows her grandmother's lawn, she volunteers to mow a neighbor's lawn as well. If she pushes the mower with the same force as before and moves it over a total of 234 meters, how much work does she do mowing the neighbor's lawn? Answer: The work Clarissa does can be calculated as: Calculating Force or Distance The work equation given above can be rearranged to find force or distance if the other variables are known: Force = Work Distance Distance = Work Force After Clarissa finishes mowing both lawns, she pushes the lawn mower down the sidewalk to her own house. If she pushes the mower over a distance of 30 meters and does 2700 joules of work, how much force does she use? Substitute the known values into the equation for force: Force = Work Distance = 2700 J 30 m = 90 N Clarissa used 90-Newton force to do a 2700 Joules of work. Here is again another question you can work on, you can compare your answer with the solution provided. rdp2023 \| G8SHSCIA 23 Question: When Clarissa gets back to her house, she hangs the 200-Newton lawn mower on some hooks in the storage room. To lift the mower, she does 400 joules of work. How far does she lift the mower to hang it? Answer: Substitute the known values into the equation for distance: Distance = Work Force = 400 J 200 N = 2 meters Process Questions 1\. Write the equation for calculating work when force and distance are known. 2\. What is the SI unit for work? What does it represent? FORMATIVE ASSESSMENT 2 Work - Problem Set Solve the following problems about Work. Make sure to include the correct units and symbols. All entries should be correct and complete. Given (1 point), Unknown (1 point), Formula (1 point), Solution (1 point) and Answer (1 point). In cases wherein your answer is correct but you have a wrong or incomplete solution no points will be given for these parts. 1\. You push a table through 3m with a force of 30N. How much work have you done on the table? The table fails to accelerate continuously due to friction. G: U: F: S: A: 2\. Angelo does 15 Joules of work to push a pencil over 1 meter. How much force did he use? G: U: F: S: A: 3\. Kyla uses a force of 25 Newtons to lift her grocery bag while doing 50 Joules of work. How far did she lift the grocery bag? G: U: F: S: A: rdp2023 \| G8SHSCIA 24 Defining Power Power is a measure of the amount of work that can be done in a given amount of time. Power can be represented by the equation: Power = Work Time In this equation, work is measured in joules (J) and time is measured in seconds (s), so power is expressed in joules per second (J/s). This is the SI unit for power, also known as the watt (W). A watt equals 1 joule of work per second. You're probably already familiar with watts. Light bulbs and small appliances such as microwave ovens are labeled with the watts of power they provide. For example, the package of light bulbs in is labeled "14 watts." Question: Assume you have two light bulbs of the same type, such as two compact fluorescent light bulbs like the one pictured in the Figure above. If one light bulb is a 25-watt bulb and the other is a 60- watt bulb, which bulb produces brighter light? Answer: The 60-watt bulb is more powerful, so it produces brighter light. Compared with a less powerful device, a more powerful device can either do more work in the same time or do the same work in less time. For example, compared with a low-power microwave oven, a high-power microwave oven can cook more food in the same time or the same amount of food in less time. Calculating Power from Work and Time Power can be calculated using the formula above if the amount of work and time are known. Recall also that work is computed by multiplying force and distance. For example, assume that a microwave oven does 24,000 joules of work in 30 seconds. Then the power of the microwave is: Power = Work Time = 2400 J 30 s = 80 J s , or 80 Watts Here are other examples for you: Question 1: Another microwave oven does 5,000 joules of work in 5 seconds. What is its power? G: W = 5, 000 J; t = 5 s U: P F: P = W/t S: Power = Work Time = 5000 J 5 s = 1000 J s , or 1000 Watts Answer 1: The power of the other microwave oven is: 1000 J/s or 1000 Watts. Please remember that 1 J/s is equivalent to 1 Watt (W). Question 2: Which microwave oven, 80-Watt or the 1000-Watt will heat the same amount of food in less time? Answer 2: The 1000-watt microwave oven has more power, so it will heat the same amount of food in less time. rdp2023 \| G8SHSCIA 25 Work = Power × Time G: P = 1000 W; t = 20 s U: W F: P = W/t; W= Pt S: W = 1000 J/s × 20 s = 20,000 J A: W = 20,000 J Given: F = 100 000 N; v = 250 m/s Unknown: P Formula: P = Fv Solution: P = (100 000 N)(250 m/s) Answer: P = 25 000 000 W Calculating Power from Force and Velocity When a constant force performs work on an object and moves it at a constant rate, the power developed is equal to the product of the force and velocity. In terms of force, P = F.d t and d t = v therefore, P = F. v This equation reveals that a powerful machine is both strong and fast. This means that a machine that is strong enough to apply a large amount of force to cause a large displacement in a short period of time is a powerful machine. Example: Question 1: How much power is developed by a jumbo jet that cruises at 250 m/s when the thrust of its engine is 100, 000 N? Calculating Work from Power and Time You can also calculate work if you know power and time by rewriting the power equation above as: For example, if you use a 1000-watt microwave oven for 20 seconds, how much work does it do? First express 1000 watts in J/s and then substitute this value for power the work equation: rdp2023 \| G8SHSCIA 26 Horsepower (hp) Sometimes power is measured in a unit called the horsepower. For example, the power of car engines is usually expressed in horsepowers (hp). One horsepower is the amount of work a horse can do in 1 minute. It equals 746 watts of power. Compare the Hp in the two pictures below, the horse driven carriage and the tractor. The horse-driven carriage provides 2 Hp while the tractor has 180 Hp. Sources:https://www.pexels.com/photo/two-man-on-a-carriage-with-horse-636012/ - horse carriage https://www.pexels.com/photo/green-tractor-plowing-the-fields-on-focus-photography-2933243/ Let us have another example: Question: If the team of horses and the tractor do the same amount of work plowing a field, which will get the job done faster? Answer: The tractor will get the job done faster because it has more power. In fact, because the tractor has 40 times the power of the six-horse team, ideally it can do the same work 40 times faster! Process Questions 1\. What is power? What is the SI unit for power? 2\. How much power does a toaster have if it does 1,000 joules of work in 30 seconds? 3\. How much work can be done in 30 seconds by a 1000-watt microwave oven? 4\. Lamar's mom has a car with a 182-horsepower engine. How many watts of power is that? Figure 3 A horse carriage Figure 4 Tractor for modern day farming rdp2023 \| G8SHSCIA 27 FORMATIVE ASSESSMENT 3 Power - Problem Set Solve the following problems about Power. Make sure to include the correct units and symbols. All entries should be correct and complete. Given (1 point), Unknown (1 point), Formula (1 point), Solution (1 point) and Answer (1 point). In cases wherein your answer is correct but you have a wrong or incomplete solution no points will be given for these parts. 1\. A constant force of 2000N pulls a crate along a level floor a distance of 10m in 50s. What is the power used? G: U: F: S: A: 2\. A new conveyor system at the local packaging plan will utilize a motor-powered mechanical arm to exert an average force of 890N to push large crates a distance of 12 meters in 22 seconds. Determine the power output required of such a motor. G: U: F: S: A: Defining Energy Energy is defined in science as the ability to move matter or change matter in some other way. Energy can also be defined as the ability to do work, which means using force to move an object over a distance. When work is done, energy is transferred from one object to another. Figure 5 When the boy in the picture on the right force to swing the racket, he transfers some of his energy to the racket. Source: https://www.pexels.com/photo/man-playing-tennis-1277397/ - Question: It takes energy to play tennis. Where does this boy get his energy? Answer: He gets energy from the food he eats. SI Unit for Energy Because energy is the ability to do work, it is expressed in the same unit that is used for work. The SI unit for both work and energy is the joule (J), or Newton ∙ meter (N ∙ m). One joule is the amount of energy needed to apply a force of 1 Newton over a distance of 1 meter. For example, suppose the boy in the Figure above applies 20 Newtons of force to his tennis racket over a distance of 1 meter. The energy needed to do this work is 20 N ∙m, or 20 J. Energy Has Many Forms When asked about the different sources of energy, you might enumerate batteries and the sun and many more. This makes us realize that energy can take different forms. For example, when the boy swings his tennis racket, the energy of the moving racket is an example of mechanical energy. To move his racket, the boy needs energy stored in food, which is an example of chemical energy. Other forms rdp2023 \| G8SHSCIA 28 of energy include electrical, thermal, light, and sound energy. The different forms of energy can also be classified as either kinetic energy or potential energy. Kinetic energy is the energy of moving matter. Potential energy is energy that is stored in matter. Question 1: Is the chemical energy in food kinetic energy or potential energy? Answer: The chemical energy in food is potential energy. It is stored in the chemical bonds that make up food molecules. The stored energy is released when we digest food. Then we can use it for many purposes, such as moving (mechanical energy) or staying warm (thermal energy). Question 2: What is an example of kinetic energy? Answer: Anything that is moving has kinetic energy. An example is a moving tennis racket. Defining Kinetic Energy Kinetic energy is the energy of moving matter. Anything that is moving has kinetic energy---from atoms in matter to stars in outer space. Things with kinetic energy can do work. For example, the spinning saw blade in the photo above is doing the work of cutting through a piece of metal. Calculating Kinetic Energy The amount of kinetic energy in a moving object depends directly on its mass and velocity. An object with greater mass or greater velocity has more kinetic energy. You can calculate the kinetic energy of a moving object with this equation: Kinetic Energy (KE) = 1 2 mass X velocity2 or KE = 1 2 mv 2 This equation shows that an increase in velocity increases kinetic energy more than an increase in mass. If mass doubles, kinetic energy doubles as well, but if velocity doubles, kinetic energy increases by a factor of four. That's because velocity is squared in the equation. Let's consider an example. Juan is running on the beach with his dad. Juan has a mass of 40 kg and is running at a velocity of 1 m/s. How much kinetic energy does he have? Substitute these values for mass and velocity into the equation for kinetic energy: G: m = 40 kg; v = 1 m/s U: KE F: KE = 1 2 mv 2 S: KE = 1 2 mv 2 = 1 2 40 kg X 1 m/s 2 = 20 Nm or 20J A: KE= 20J Notice that the answer is given in joules (J), or N m, which is the SI unit for energy. One joule is the amount of energy needed to apply a force of 1 Newton over a distance of 1 meter. What about Juan's dad? His mass is 80 kg, and he's running at the same velocity as Juan (1 m/s). Because his mass is twice as great as Juan's, his kinetic energy is twice as great: G: m = 80kg; v = 1 m/s U: KE F: KE = 1 2 mv 2 S: KE = 1 2 mv 2 = 1 2 80 kg X 1 m/s 2 = 40 Nm or 40J A: KE = 40J rdp2023 \| G8SHSCIA 29 Let us now try this example: Question: What is Juan's kinetic energy if he speeds up to 2 m/s from 1 m/s? Answer: By doubling his velocity, Juan increases his kinetic energy by a factor of four: G: m = 80kg; v = 1 m/s U: KE F: KE = 1 2 mv 2 S: KE = 1 2 mv 2 = 1 2 80 kg X 2 m/s 2 = 80 Nm or 80J A: KE = 80J Process Questions 1\. What is kinetic energy? 2\. The kinetic energy of a moving object depends on what factors? FORMATIVE ASSESSMENT 4 Kinetic Energy- Problem Set Calculate for the Kinetic Energy of the given problems. Make sure to include the correct units and symbols. All entries should be correct and complete. Given (1 point), Unknown (1 point), Formula (1 point), Solution (1 point) and Answer (1 point). In cases wherein your answer is correct but you have a wrong or incomplete solution no points will be given for these parts. 1-3. Calculate the kinetic energy of a 45g golf ball travelling at: a) 20m/s, b) 40m/s, c) 60m/s G: U: F: S: A: 4\. Missy Diwater, the former platform diver for the Ringling Brothers' Circus had a kinetic energy of 15,000 J just prior to hitting the bucket of water. If Missy's mass is 50 kg, what was her velocity? G: U: F: S: A: Defining Potential Energy Have you seen a swimmer positioned on a diving board, ready to jump? After she dives down and is falling toward the water, she'll have kinetic energy, or the energy of moving matter. But even as she is momentarily stopped high above the water, she has energy. Do you know why? The diver has energy because of her position high above the pool. The type of energy she has is called potential energy. Potential energy is energy that is stored in a person or object. Often, the person or object has potential energy because of its position or shape. rdp2023 \| G8SHSCIA 30 Gravitational potential energy (GPE) = weight × height GPE = mgh What is it about the diver's position that gives her potential energy? That is because the diver is high above the water, she has the potential to fall toward Earth because of gravity. This gives her potential energy. Gravitational Potential Energy Potential energy due to the position of an object above Earth's surface is called gravitational potential energy. Like the diver on the diving board, anything that is raised up above Earth's surface has the potential to fall because of gravity. You can see another example of people with gravitational potential energy in the pictures below. Figures 6 & 7 Both the sled and the gymnast have gravitational potential energy. Sources: https://www.maxpixel.net/Sweden-Snow-Winter-Sled-Sledding-Girls-Children-104689 https://www.pexels.com/photo/photo-of-male-gymnast-practicing-in-gym-3763700/ Gravitational potential energy depends on an object's weight and its height above the ground. It can be calculated with the equation: Consider the little girl on the sled, pictured above. She weighs 140 Newtons, and the top of the hill is 4 meters higher than the bottom of the hill. As she sits at the top of the hill, the child's gravitational potential energy is: G: W = 140kg; h= 4 m U: GPE F: GPE = mg S: GPE = (140 N) (4 m) = 560 N m A: GPE = 560 J A Newton ∙ meter is the energy needed to move a weight of 1 Newton over a distance of 1 meter. A Newton meter is also called a joule (J). Here is another example: The gymnast on the balance beam pictured in the Figure above weighs 360 Newtons. If the balance beam is 1.2 meters above the ground, what is the gymnast's gravitational potential energy? Answer: Her gravitational potential energy is: rdp2023 \| G8SHSCIA 31 G: W = 360N; h = 1.2 m U: GPE F: GPE = mgh S: GPE = (360 N)(1.2 m) = 432 N m A: GPE = 432 J Elastic Potential Energy Potential energy due to an object's shape is called elastic potential energy. This energy results when an elastic object is stretched or compressed. The farther the object is stretched or compressed, the greater its potential energy is. A point will be reached when the object can't be stretched or compressed any more. Then it will forcefully return to its original shape. Look at the pogo stick in the Figure on the right. Its spring has elastic potential energy when it is pressed down by the girl\'s weight. When it can't be compressed any more, it will spring back to its original shape. The energy it releases will push the pogo stick---and the girl---off the ground. Figure 7 This pogo stick stores energy in its spring. Source:https://www.smythstoys.com/ie/en-ie/outdoor/garden- games-and-accessories/pogo-sticks/pro-sport-pogo-stick/p/144490 Question: The girl in the Figure below is giving the elastic band of her slingshot potential energy by stretching it. She's holding a small stone against the stretched band. What will happen when she releases the band? Answer: The elastic band will spring back to its original shape. When that happens, watch out! Some of the band's elastic potential energy will be transferred to the stone, which will go flying through the air. Figure 8 A girl with her slingshot Source: https://www.istockphoto.com/photo/girl-with-slingshot-gm182801843- 13427100 Other Forms of Potential Energy All of the examples of potential energy described above involve movement or the potential to move. The form of energy that involves movement is called mechanical energy. Other forms of energy also involve potential energy, including chemical energy and nuclear energy. Chemical energy is stored in the bonds between the atoms of compounds. For example, food and batteries both contain chemical energy. Nuclear energy is stored in the nuclei of atoms because of the strong forces that hold the nucleus together. Nuclei of radioactive elements such as uranium are unstable, so they break apart and release the stored energy. rdp2023 \| G8SHSCIA 32 Process Questions 1\. What is potential energy? 2\. Compare and contrast gravitational and elastic potential energy, and give an example of each. 3\. Why does food have potential energy? FORMATIVE ASSESSMENT 5 Potential Energy - Problem Set Solve for the Potential Energy of the given problems. Make sure to include the correct units and symbols. All entries should be correct and complete. Given (1 point), Unknown (1 point), Formula (1 point), Solution (1 point) and Answer (1 point). In cases wherein your answer is correct but you have a wrong or incomplete solution no points will be given for these parts. 1.Richard wants to know how much potential energy his cat has when it climbs to the top of the tree near his house. The tree is 15 meters high and the cat has a mass of 5 kilograms. How much potential energy does the cat have? G: U: F: S: A: 2\. The potential energy of an apple is 6 J. The apple is 3 m high. What is the mass of the apple? G: U: F: S: A: rdp2023 \| G8SHSCIA 33 INTEGRATION (Transfer) You have completed this lesson. Before you go to the next lesson, you have to answer the post- assessment. SUMMATIVE ASSESSMENT 2 A. Matching Type. Match the quantities in column A with their SI units in column B. You can have the same answer for different numbers. Use capital letters for your answers. A B \_\_\_\_\_\_\_\_ 1. Acceleration A. Watt(W) \_\_\_\_\_\_\_\_ 2. Displacement B. Joule (J) \_\_\_\_\_\_\_\_ 3. Energy C. Horsepower (hp) \_\_\_\_\_\_\_\_ 4. Friction D. Second(s) \_\_\_\_\_\_\_\_ 5. Force E. Newton (N) \_\_\_\_\_\_\_\_ 6. Force constant F. Kilometer (km) \_\_\_\_\_\_\_\_ 7. Mass G. Kilograms (kg) \_\_\_\_\_\_\_\_ 8. Power H. Meter per second (m/s) \_\_\_\_\_\_\_\_ 9. Time I. Newton per meter (N/m) \_\_\_\_\_\_\_\_ 10. Weight J. Meter per second squared (m/s2 ) \_\_\_\_\_\_\_\_ 11. Work K. Hour \_\_\_\_\_\_\_\_ 12. Velocity L. Meter B. Multiple Choice (2 points each) Read and understand the following question/statement. Identify the answer to the question or complete a statement by choosing the letter of your answer from the given options. 1\. Amy uses 20N of force to push a lawn mower 10 meters. How much work does she do?? A. 200 kg B. 200 J C. 2 N D. 2 N.m 2\. How much work does an elephant do while moving a tree branch 20 meters with a pulling force of 20N? A. 1 J B. 40 J C.400 J D. 4000 J 3\. A baseball player does 1, 050 J of work when hitting a baseball into left field. Assuming the baseball landed 100 meters away from home plate, how much force did the player use to hit the ball? A. 10. 5 J B.10. 5 m C. 10.5 N D. 10.5 W 4\. Kyla uses a force of 25 Newtons to lift her grocery bag while doing 50 Joules of work. How far did she lift the grocery bag? A. 1, 250 m B. 75 m C. 25 m D. 2 m 5\. What power is expended in lifting a 50 N weight to a height of 20 m in one minute? (Clue: convert time to seconds) A. 400 J B. 400 W C. 6.667 J D. 6.667 W 6\. Missy Diwater, the former platform diver for the Ringling Brothers' Circus had a kinetic energy of 15,000 J just prior to hitting the bucket of water. If Missy's mass is 50 kg, what was her velocity? A. 24.49 m/s B. 24.49 m2 /s2 C.600 m/s D. 600 m2 /s2 rdp2023 \| G8SHSCIA 34 7\. Richard wants to know how much potential energy his cat has when it climbs to the top of the tree near his house. The tree is 15 meters high and the cat has a mass of 5 kilograms. How much potential energy does the cat have? (Use g = 9.8 m/s2 ) A. 735 kg B. 753 kg C. 735 J D. 753 N 8\. Calculate the kinetic energy (KE) of a 1000 kg car traveling at 160 m/s. A. 12, 000 000 J B. 12, 600 000 J C. 12, 800 000 J D. 13, 000 000 J rdp2023 \| G8SHSCIA 35 LESSON 3 SOUND AND LIGHT Objectives: In this lesson, you are expected to 1\. describe sound. 2\. explain why sound travels faster in solid. 3\. explain the equation for wave velocity. 4\. describe what makes up white light. 5\. define refraction. 6\. explain what happens to light when it travels through the atmosphere. 7\. explain the scattering of light. INTRODUCTION (Explore) KWL Chart Write what you know as answers to the given questions. Questions K What I know W L Which phase of matter does sound travels the fastest? At which temperature will sound travels the fastest? Which two factors affect the speed of sound? How do raindrops make a rainbow? What two things about the atmosphere affect the color of the sky you see? Why does a green leaf look color green? How do polarizing sunglasses reduce glare? INTERACTION (Firm-up & Deepen) Reading Activity SOUND WAVE Crack! Crash! Thud! That's what you'd hear if you were in the forest when this old tree cracked and came crashing down to the ground. But what if there was nobody there to hear the tree fall? Would it still make these sounds? This is an old riddle. To answer the riddle correctly, you need to know the scientific definition of sound. Defining Sound In science, sound is defined as the transfer of energy from a vibrating object in waves that travel through matter. Most people commonly use the term sound to mean what they hear when sound waves enter their ears. The tree above generated sound waves when it fell to the ground, so it made sound according to the scientific definition. But the sound wasn't detected by a person's ears if there was rdp2023 \| G8SHSCIA 36 Figure 1 Vibrating guitar string nobody in the forest. So, the answer to the riddle is both yes and no! All sound waves begin with vibrating matter. Have you tried playing the guitar? Plucking the string makes it vibrate. The diagram below the figure shows the wave generated by the vibrating string. The moving string repeatedly pushes against the air particles next to it, which causes the air particles to vibrate. The vibrations spread through the air in all directions away from the guitar string as longitudinal waves. In longitudinal waves, particles of the medium vibrate back and forth parallel to the direction that the waves travel. Question: If there were no air particles to carry the vibrations away from the guitar string, how would sound reach the ear? Answer: It wouldn't unless the vibrations were carried by another medium. Sound waves are mechanical waves, so they can travel only though matter and not through empty space. Sound Waves and Matter Most of the sounds we hear reach our ears through the air, but sounds can also travel through liquids and solids. If you swim underwater---or even submerge your ears in bathwater---any sounds you hear have traveled to your ears through the water. Some solids, including glass and metals, are very good at transmitting sounds. Foam rubber and heavy fabrics, on the other hand, tend to muffle sounds. They absorb rather than pass on the sound energy. Question: How can you tell that sounds travel through solids? Answer: One way is that you can hear loud outdoor sounds such as sirens through closed windows and doors. You can also hear sounds through the inside walls of a house. For example, if you put your ear against a wall, you may be able to eavesdrop on a conversation in the next room---not that you would, of course. Source: CK-12. (2019, September 27). Sound Waves. https://flexbooks.ck12.org/cbook/ck-12-middle-school-physical-science- flexbook-2.0/section/17.1/primary/lesson/sound-waves-ms-ps Process Questions 1\. How is sound defined in science? 2\. How does this definition differ from the common meaning of the word? 3\. Hitting a drum, generates sound waves. Create a diagram to show how the sound waves begin and how they reach a person's ears.1. 4\. How do you think earplugs work? rdp2023 \| G8SHSCIA 37 Reading Activity SPEED OF SOUND Has this ever happened to you? You see a flash of lightning on the horizon, but several seconds pass before you hear the rumble of thunder. The reason? The speed of light is much faster than the speed of sound. What Is the Speed of Sound? The speed of sound is the distance that sound waves travel in a given amount of time. You'll often see the speed of sound given as 343 meters per second. But that's just the speed of sound under a certain set of conditions, specifically, through dry air at 20 °C. The speed of sound may be very different through other matter or at other temperatures. Speed of Sound in Different Media Sound waves are mechanical waves, and mechanical waves can only travel through matter. The matter through which the waves travel is called the medium (plural, media). The Table below gives the speed of sound in several different media. Generally, sound waves travel most quickly through solids, followed by liquids, and then by gases. Particles of matter are closest together in solids and farthest apart in gases. When particles are closer together, they can more quickly pass the energy of vibrations to nearby particles. Medium (20 °C) Speed of Sound Waves (m/s) Dry Air 343 Water 1437 Wood 3850 Glass 4540 Aluminum 6320 Question: The table gives the speed of sound in dry air. Do you think that sound travels more or less quickly through air that contains water vapor? (Hint: Compare the speed of sound in water and air in the table.) Answer: Sound travels at a higher speed through water than air, so it travels more quickly through air that contains water vapor than it does through dry air. Temperature and Speed of Sound The speed of sound also depends on the temperature of the medium. For a given medium, sound has a slower speed at lower temperatures. You can compare the speed of sound in dry air at different temperatures in the following Table below. At a lower temperature, particles of the medium are moving more slowly, so it takes them longer to transfer the energy of the sound waves. Temperature of Air Speed of Sound Waves (m/s) 0 °C 331 20 °C 343 100 °C 386 Question: What do you think the speed of sound might be in dry air at a temperature of -20 °C? Answer: For each 1 degree Celsius that temperature decreases, the speed of sound decreases by 0.6 m/s. So sound travels through dry, -20 °C air at a speed of 319 m/s. Source: CK-12. (2019, September 27). Sound Waves. https://flexbooks.ck12.org/cbook/ck-12-middle-school-physical- science-flexbook-2.0/section/17.1/primary/lesson/sound-waves-ms-ps rdp2023 \| G8SHSCIA 38 Visualization of different wavelengths of color Process Questions 1\. What is the speed of sound in dry air at 20 °C? 2\. Why are sound waves transmitted faster in solids? 3\. How does temperature affect the speed of sound in gases? Reading Activity LIGHT The rainbow contains all the colors that you can see. In fact, a rainbow contains all of the colors of visible light. Wavelength and Color Visible light is light that has wavelengths that can be detected by the human eye. The wavelength of visible light determines the color that the light appears. As you can see in the Figure below, light with the longest wavelength appears red, and light with the shortest wavelength appears violet. In between are all the other colors of light that we can see. Only seven main colors of light are actually represented in the diagram. Separating Colors of Light A prism can be used to separate visible light into its different colors. A prism is a pyramid-shaped object made of transparent matter, usually clear glass or plastic. Matter that is transparent allows light to pass through it. A prism transmits light but slows it down. When light passes from air to the glass of the prism, the change in speed causes the light to change direction and bend. Different wavelengths of light bend at different angles. This makes the beam of light separate into light of different wavelengths. What we see is a rainbow of colors. The process by which light is separated into its colors due to differences in degrees of refraction is called dispersion. Prism splitting light Question: Recall how a rainbow looked like. Do you see all the different colors of light, from red at the top to violet at the bottom? What causes a rainbow to form? Answer: Individual raindrops act as tiny prisms. They separate sunlight into its different wavelengths and create a rainbow of colors. rdp2023 \| G8SHSCIA 39 Leaves are green because they reflect green light Source: https://www.pexels.com/photo/green-leafed-plants-2453551/ - Sample of stained glass window from a cathedral Source: https://www.pexels.com/photo/architecture-art-cathedral-chapel-390052/ Colors of Objects An opaque object is one that doesn't let light pass through it. Instead, it reflects or absorbs the light that strikes it. Many objects, such as the leaves pictured in the Figure below, reflect just one or a few wavelengths of visible light and absorb the rest. The wavelengths that are reflected determine the color that an object appears to the human eye. For example, the leaves appear green because they reflect green light and absorb light of other wavelengths. A transparent or translucent material, such as window glass, transmits some or all of the light that strikes it. This means that the light passes through the material rather than being reflected by it. In this case, we see the material because of the transmitted light. Therefore, the wavelength of the transmitted light determines the color that the object appears. Look at the beautiful stained glass windows in the Figure below. The different colors of glass transmit light of different colors. Colored translucent and transparent materials appear the way they do because of the way they transmit light The color of light that strikes an object may also affect the color that the object appears. For example, if only blue light strikes green leaves, the blue light is absorbed and no light is reflected. Questions: What color do you see if an object absorbs all of the light that strikes it? rdp2023 \| G8SHSCIA 40 Answer: When all of the light is absorbed, none is reflected, so the object looks black. But black isn't a color of light. Black is the absence of light. The Colors We See The human eye can distinguish only red, green, and blue light. These three colors are called the primary colors of light. All other colors of light can be created by combining the primary colors. Look at the Venn diagram below. Red and green light combine to form yellow light. Red and blue light combine to form magenta light, and blue and green light combine to form cyan light. Yellow, magenta, and cyan are called the secondary colors of light. Look at the center of the diagram, where all three primary colors of light combine. The result is white light. The three primary colors Pigments Many objects have color because they contain pigments. A pigment is a substance that colors materials by reflecting light of certain wavelengths and absorbing light of other wavelengths. A very common pigment is the dark green pigment called chlorophyll, which is found in plants. Chlorophyll absorbs all but green wavelengths of visible light. Pigments are also found in many manufactured products. They are used to color paints, inks, and dyes. Just three pigments, called primary pigments, can be combined to produce all other colors. The primary colors of pigments are the same as the secondary colors of light: cyan, magenta, and yellow. Question: A color printer needs just three colors of ink to print all of the colors that we can see. Which colors are they? Answer: The three colors of ink in a color printer are the three primary pigment colors: cyan, magenta, and yellow. These three colors can be combined in different ratios to produce all other colors, so they are the only colors needed for full-color printing. White light is composed of an infinite number of individual colors. Your eye blends the colors and your brain "sees" white light. A prism, such as the one on Pink Floyd\'s album cover, is able to resolve the light back into individual colors. Source: CK-12. (n.d.). Light and Color.https://www.ck12.org/c/physical-science/light-and-color/lesson/Color-MS- PS/?referrer=featured\_content rdp2023 \| G8SHSCIA 41 Diagram of an electromagnetic wave Process Questions 1\. What determines the color of visible light? 2\. Which color of light has the longest wavelength? Which color has the shortest wavelength? 3\. How does a prism separate visible light into its different colors? 4\. To a person with normal vision, green apple appears green. Explain why. 5\. The human eye can detect only three colors of light. What three colors are they? How can we perceive other colors of light? 6\. What are pigments? Identify the primary colors of pigments. If you combined the three primary pigment colors, what color would you get? Fundamentals of Light Electromagnetic Radiation Spectrum We only see objects that have light waves that travel from them to our eyes. Objects either generate light or reflect it. Light is generated by incandescent and fluorescent lamps, light emitting diodes, flames, very hot objects, and even some animals. Our major source of light is the sun. Light is a small fraction of the energy we call electromagnetic radiation. Electromagnetic radiation is a form of energy that consists of oscillating electric and magnetic fields traveling at the speed of light. Electromagnetic waves carry this energy from one place to another and are similar to waves in a rope. Unlike the wave in a rope, however, electromagnetic waves do not require a medium to travel; the most prevalent electromagnetic waves we experience travel through the vacuum of outer space from the sun. The energy of an electromagnetic wave travels in a straight line along the path of the wave. The moving light wave has associated with it an oscillating electric field and an oscillating magnetic field. Scientists often represent the electromagnetic wave with the image below. The black line represents the straight path of the light itself. Along this path, there exists an electric field that will reach a maximum positive charge, slowly collapse to zero charge, and then expand to a maximum negative charge. Similarly, there is an changing magnetic field that oscillates from maximum north pole field to maximum south pole field. Along the path of the electromagnetic wave, these changing fields repeat, oscillating over and over again. However, the oscillating electric and magnetic fields demonstrate a weaving pattern that is not the way light travels. For an electromagnetic wave, the crests and troughs represent the oscillating fields, not the path of the light. Although light waves look different from waves in a rope, we still characterize light waves by their wavelength, frequency, and velocity. We can measure along the path of the wave the distance the wave travels between one crest and the succeeding crest, which is the wavelength of the electromagnetic radiation. Like transverse waves through a medium, the frequency of electromagnetic rdp2023 \| G8SHSCIA 42 waves is the number of full cycles of waves that pass a certain point in a set unit of time. The velocity for all electromagnetic waves traveling through a vacuum is the same: 3.00×108 m/s, which is symbolized by the lower case c. The relationship, then, for the velocity, wavelength, and frequency of electromagnetic waves is: c=λf. The wavelength and frequency of light are inversely proportional, just like in sound waves. The entire spectrum of electromagnetic waves includes very low energy electric waves up to very high energy gamma rays. As you probably know, ultraviolet rays, X-rays, and radio waves are also waves on the electromagnetic spectrum. The full electromagnetic spectrum is shown in the figure below. You can see that visible light is a very small fraction of the electromagnetic spectrum. Polarization Remember the illustration of electromagnetic radiation? These electric and magnetic waves may oscillate in any direction. That is, the oscillating fields may be oscillating vertically, horizontally, and in every other direction. Light typically consists of oscillating fields in all directions, but always travels in a straight line. Filters can be constructed such that only light with the fields oscillating in a certain direction can pass through the filter. This is much like having a large number of ropes passing through the slots in a picket fence. The ropes have transverse waves oscillating in all possible directions moving toward the fence. When the waves encounter the fence, only the oscillations that are vertical and fit through the slots in the fence will be allowed to pass through. Light that has all its field oscillations in the same direction is said to be polarized. Figure 2. Light spectrum rdp2023 \| G8SHSCIA 43 Process Questions 1\. Sound doesn't travel through a vacuum because there are no molecules to carry it. How do we know that light does travel through a vacuum? 2\. What is the range of wavelength of electromagnetic radiation the human eye can detect? 3\. What was changed in the equation v=λf in this concept? 4\. What color of visible light has the shortest wavelength? 5\. How are we able to see objects that do not generate light? 6\. Of what colors does white light consist? 7\. Why can't sound waves be polarized? 8\. What happens to the wavelength of light as the frequency increases? 9\. The sky appears darker when viewed through a polarizing filter. Why? 10\. What color will a yellow banana appear when illuminated by a\. white light? b. yellow light? c. blue light? FORMATIVE ASSESSMENT 6 KWL Chart Please go back to your KWL Chart and answer the last two columns. Questions K W What I Learned L What I want to learn more Which phase of matter does sound travels the fastest? At which temperature will sound travels the fastest? Which two factors affect the speed of sound? How do raindrops make a rainbow? What two things about the atmosphere affect the color of the sky you see? Why does a green leaf look color green? How do polarizing sunglasses reduce glare? INTEGRATION (Transfer) You have completed this lesson. Before you go to the next lesson, you have to answer the post- assessments. SUMMATIVE ASSESSMENT 3 Multiple Choice. Choose the letter that corresponds to the correct answer. \_\_\_\_\_ 1. In which medium does sound travel faster? A. air B. glass C. steel D. water \_\_\_\_\_ 2. What happens to wavelength as frequency increases? A. increases C. increases then decreases B. decreases D. decreases then increases rdp2023 \| G8SHSCIA 44 \_\_\_\_\_ 3. At which temperature will sound travel faster? A. 10 ̊C B. 40 ̊C C. 60 ̊C D. 80 ̊C \_\_\_\_\_ 4. Which is NOT true about sound waves? A. Sound waves are used to locate submarines, schools of fish and other objects underwater. B. Sound waves are used in ultrasound. C. Sound waves do not need a medium to travel. D. Sound waves are mechanical waves. \_\_\_\_\_ 5. What do the following -- drapes, furniture and carpets - do to sound waves? A. absorb B. diffract C. reflect D. refract \_\_\_\_\_ 6.How will you describe an object that doesn't let light pass through it but rather reflects or absorbs the light that strikes it? A. opaque B. distorted C. translucent D. transparent \_\_\_\_\_ 7.What color is formed when red and green light is combined? A. blue B. cyan C. magenta D. yellow \_\_\_\_\_ 8. A color printer needs just three colors of ink to print all the colors that we can see. Which colors are they? A. blue, cyan, magenta C. cyan, magenta, yellow B. magenta, red, yellow D. red, blue, yellow \_\_\_\_\_ 9. In rainbow formation, what acts as prism? A. clouds B. fog C. raindrops D. sunlight \_\_\_\_ 10. Which of the following color components of visible light has the longest wavelength? A. blue B. indigo C. red D. violet Alternate Response. Read and understand the following statement. Write TRUE if it expresses a correct thought and FALSE if otherwise. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 1. Sound are mechanical waves. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 2. Sound can travel even in a vacuum. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 3. Sound waves travel faster in solids. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 4. Sound has a lower speed at higher temperatures. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 5. Light travels faster than sound. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 6. You hear the rumble of thunder before you can see the flash of lightning. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 7. Black is a color of light. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 8. Among the color components of visible light, violet has the longest wavelength. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 9. An opaque object doesn't let light pass through it. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 10. White light is composed of different colors. rdp2023 \| G8SHSCIA 45 LESSON 4 HEAT AND TEMPERATURE Objectives: In this lesson you are expected to: 1\. explain how explain what combustion is. 2\. define heat. 3\. distinguish heat and thermal energy 4\. explain the effects of excessive heat in the human body and in the environment. INTRODUCTION (Explore) Let's start our lesson with a trick question: What contains more heat, a cup of coffee or a glass of iced tea? Just like work, heat is often used in everyday language but has a different meaning in science. Thermodynamics, a branch of physics, deals with how heat is transferred between different systems and how work is done in the process. In this lesson, we are going to encounter and learn some terms related to heat. INTERACTION (Firm-up & Deepen) In Grade 7, you learned about the different conditions necessary for heat transfer. Now, you will learn about Heat and Temperature. This reading activity will provide the knowledge about heat and temperature. Reading Activity HEAT AND TEMPERATURE Key Points: HEAT is thermal energy transferred from a hotter system to a cooler system that are in contact. TEMPERATURE is a measure of the average kinetic energy of the atoms or molecules of the system. The ZEROTH LAW OF THERMODYNAMICS says that no heat is transferred between two objects in thermal equilibrium; therefore, they are the same temperature. We can calculate the heat released or absorbed using the specific heat capacity (C), the mass of the substance (m), and the change in temperature (∆T), and the equation is: Heat in thermodynamics Scientists define heat as thermal energy transferred between two systems at different temperatures that come in contact. Heat is written with the symbol q or Q, and it has units of Joules (J) Heat is sometimes called a process quantity, because it is defined in the context of a process by which energy can be transferred. We don't talk about a cup of coffee containing heat, but we can talk about the heat transferred from the cup of hot coffee to your hand. Heat is also an extensive property, so the change in temperature resulting from heat transferred to a system depends on how many Q = C x M x ∆T rdp2023 \| G8SHSCIA 46 molecules are in the system. Relationship between heat and temperature Heat and temperature are two different but closely related concepts. Note that they have different units: temperature typically has units of degrees Celsius or Kelvin, and heat has units of energy, Joules. Temperature is a measure of the average kinetic energy of the atoms or molecules in the system. The water molecules in cup of hot coffee have a higher kinetic energy than the water molecules in a cup of iced tea, which also means they are moving at a higher velocity. Temperature is also an intensive property, which means that temperature doesn't change no matter how much of a substance you have. This is why chemists can use the melting point to help identify a pure substance -- minus the temperature at which melts is a property of the substance with no dependence on the mass of the sample. On the atomic level, the molecules in each object are constantly in motion and colliding with each other. Every time molecules collide kinetic energy can be transferred. When the two systems are in contact, heat will be transferred through molecular collisions from the hotter system to the cooler system. The thermal energy will flow in that direction until two objects are at the same temperature. When the two systems in contact are the same temperature, we say they are in thermal equilibrium. Zeroth law of thermodynamics: Defining thermal equilibrium The zeroth law of thermodynamics defines thermal equilibrium within an isolated system. The zeroth law says when two objects at thermal equilibrium are in contact, there is no net heat transfer between the objects; therefore, they are the same temperature. Another way to state the zeroth law is to say that if two objects are both separately in thermal equilibrium with a third object, then they are in thermal equilibrium with each other. The zeroth law allows us to measure the temperature of objects. Any time we use a thermometer, we are using the zeroth law of thermodynamics. Let's say we are measuring the temperature of water bath. In order to make sure the reading is accurate, we usually want to wait for the temperature reading to stay constant. We are waiting for the thermometer and the water to reach thermal equilibrium! At thermal equilibrium, the temperature of thermometer bulb and the water will be the same, and there should be no net heat transfer from one object to the other (assuming no other loss of heat to the surroundings). Heat capacity: Converting between heat and change in temperature How can we measure heat? Here are some things we know about heat so far: When a system absorbs or loses heat, the average kinetic energy of the molecules will change. Thus, heat transfer results in a change in the system's temperature as long as the system is not undergoing a phase change. The change in temperature resulting from heat transferred to or from a system depends on how many molecules are in the system. We can use the thermometer to measure the change in a system's temperature. How can we use the change in temperature to calculate heat transferred? In order to figure out how the heat transferred to a system will change the temperature of the system, we need to know at least 2 things: 1\. The number of molecules in the system; and 2\. The heat capacity of the system. The heat capacity tells us how much energy is needed to change the temperature of a given substance assuming that no phase changes are occurring. There are two main ways that heat capacity is reported. 1\. The specific heat capacity (also called specific heat) Represented by c or C It is how much energy is needed to increase the temperature of one gram of a substance by 10C or 10K. rdp2023 \| G8SHSCIA 47 Specific heat capacity usually has units of Joule Gram.K 2\. The molar heat capacity Represent by cmol or Cmol It is measured the amount of thermal energy it takes to raise the temperature of one mole of a substance by 10C or 10K. It has a unit of Joule Mol.K For example, the heat capacity of Lead might be given as the specific heat capacity, 0.129 Joule Gram.K or the molar heat capacity is 26.65 Joule Mol.K. Calculating Q using the heat capacity We can use the heat capacity to determine the heat released or absorbed by a material using the following formula: Where, Q is the heat capacity (heat released or absorbed) M is the mass of the substance C is the Specific Heat of the substance ∆T is the change of temperature; Final Temperature minus Initial Temperature (Tf -- Ti) Example problem: Cooling a cup of tea Let\'s say that we have 250 ml of hot tea which we would like to cool down before we try to drink it. The tea is currently at 370oK, and we\'d like to cool it down to 350oK. How much thermal energy has to be transferred from the tea to the surroundings to cool the tea? The hot tea will transfer heat to the surroundings as it cools. We are going to assume that the tea is mostly water, so we can use the density and heat capacity of water in our calculations. The specific heat capacity of water is 4.18 joule/gram °C, and the density of water is 1.00 g/ml. We can calculate the energy transferred in the process of cooling the tea using the following steps: 1\. Calculate the mass of the substance We can calculate the mass of the tea/water using the volume and density of water: Density = mass volume ; mass = density X volume = 1 g/ml of water X 250 ml mass = 250 g 2\. Calculate the change in temperature, We can calculate the change in temperature: ∆T = Temperature final -- Temperature initial = 350oK -- 370oK ∆T = -20oK Q = C x M x ∆T rdp2023 \| G8SHSCIA 48 3\. Solve for Q Now we can solve for the heat transferred from the hot tea using the equation for heat: Q = C x M x ∆T = 4.18 Joule/gram.oK X 250 g X -20oK Q = 21000 Joule Thus, we calculated that the tea will transfer 21000 J of energy to the surroundings when it cools down from 370oK to 350oK. Source: Khan Academy. (n.d.). Heat and Temperature. https://www.khanacademy.org/science/ap-chemistry/thermodynamics- ap/internal-energy-tutorial-ap/a/heat CHANGE OF PHASE A change of phase is said to occur when matter changes from one state into another. At certain temperatures, a substance can undergo phase changes. For example, your ice cream melts and rubbing alcohol evaporates. Why do these changes in phase take place? Rubbing alcohol disappears because it undergoes change of phase from liquid to vapor or gas phase. When ice cream melts, solid changes to liquid. Thermal energy from the surroundings is absorbed by the substance undergoing a phase change. In solids, the thermal energy is absorbed by the molecules to overcome the strong force that holds them to become liquid. In liquids, the thermal energy is absorbed by molecules to break the weak attractive force that holds them to become gas. It is important to note the reverse processes of phase changes: freezing, melting, evaporation, and condensation. Freezing is a phase of change from liquid to solid. Melting is the reverse of freezing. This phase change converts solid to liquid by the application of heat. Condensation is the process by which water vapor changes to liquid. Evaporation is the change of liquid into water vapor. Hence, it is the reverse process of condensation. The amount of thermal energy absorbed by a substance in the melting process is equal to the amount of thermal energy released when the same substance undergoes freezing. The magnitudes of thermal energy released during condensation and thermal energy absorbed during evaporation are equal. Sublimation and deposition are opposite processes. Sublimation involves a change of phase from solid to gas. On the other hand, deposition is when a substance goes from gas to solid. Phase Transitions Source: https://energyeducation.ca/encyclopedia/Phase\_change rdp2023 \| G8SHSCIA 49 EFFECTS OF HEAT ON THE HUMAN BODY During very hot days, the blood vessels in your skin expand or dilate and carry the excess heat to the surface of your skin. This causes sweating. As the sweat evaporates, you feel cool. The reverse process takes place when it is cold, wherein blood vessels contract. This reduces blood flow in your skin that results to a decrease in the amount of heat released by the body. When the weather is too cold, you shiver. This is due to rapid contraction of the muscles which results in the generation of more heat. Reading Activity WHAT IS THE HEAT INDEX? \"It\'s not the heat, it\'s the humidity\". That\'s a partly valid phrase you may have heard in the summer, but it\'s actually both. The heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature. This has important considerations for the human body\'s comfort. When the body gets too hot, it begins to perspire or sweat to cool itself off. If the perspiration is not able to evaporate, the body cannot regulate its temperature. Evaporation is a cooling process. When perspiration is evaporated off the body, it effectively reduces the body\'s temperature. When the atmospheric moisture content (i.e. relative humidity) is high, the rate of evaporation from the body decreases. In other words, the human body feels warmer in humid conditions. The opposite is true when the relative humidity decreases because the rate of perspiration increases. The body actually feels cooler in arid conditions. There is direct relationship between the air temperature and relative humidity and the heat index, meaning as the air temperature and relative humidity increase (decrease), the heat index increases (decreases). Source: National Weather Service - NOAA. (n.d.). What is the heat index? https://www.weather.gov/ama/heatindex FORMATIVE ASSESSMENT 7 Constructed Response. Applying what you have learned, give your explanation to each situation. 5 - Answer is very accurate, comprehensive and well-supported; concepts are fully and properly explained; insights presented; 4 - Content is accurate, comprehensive and well-supported; concepts are fully and properly explained; 3 - Appropriate details are included; adequate explanation; 2 - Poor explanation; misinterprets the science concepts; 1 - No analysis of topic; wrong explanation 1\. How does heat affect the motion of atoms or molecules of an object? \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ rdp2023 \| G8SHSCIA 50 2\. How is Earth's temperature affected by the presence of excess carbon dioxide in the atmosphere? \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ rdp2023 \| G8SHSCIA 51 LESSON 5 ELECTRICITY Objectives: In this lesson you are expected to: 1\. describe how an electric current flow through a wire. 2\. differentiate a conductor, insulator and semiconductor. 3\. explain why electricity flow differently through different materials. 4\. explain the relationship of current, voltage and resistance. 5\. describe a series and parallel circuits and enumerate the advantage of one over the other. 6\. enumerate safety measures in using electricity. INTRODUCTION (Explore) The words that found in the table are important in understanding the lesson for the week. ACTIVITY Vocabulary building Find the meaning of the words listed on the table. Do not forget to provide your source. Word Meaning Source Electric Current Electric circuit Voltage Resistance Amperes Ohm Volts Electric power Kilowatt Kilowatt-hour Fuse Circuit breaker Short circuit Generator INTERACTION (Firm-up & Deepen) Reading Activity ELECTRIC CURRENT When lightning discharges static electricity, it transfers a great deal of electric charge all at once. Such a sudden and large discharge of electricity isn't useful. You can't plug a toaster into a lightning bolt! To power appliances and other electric devices, you need a source of electricity that provides a relatively small amount of continuously flowing electric charges. The solution is an electric current. rdp2023 \| G8SHSCIA 52 Introduction to Electric Current Electric current is a continuous flow of electric charges. Current is measured as the amount of charge that flows past a given point in a certain amount of time. The SI unit for electric current is the ampere (A), or amp. Electric current may flow in just one direction, or it may keep reversing direction. When current flows in just one direction, it is called direct current (DC). The current that flows through a battery-powered flashlight is direct current. When current keeps reversing direction, it is called alternating current (AC). The current that runs through the wires in your home is alternating current. Graphs of both types of current are shown in Figure below. Online Activity Direct current flows in one direction only, whereas alternating current keeps reversing direction.You can watch an animation of both types at http://www.youtube.com/watch?v=JZjMuIHoBeg (0:10). Explaining Electric Current Why do charges flow in an electric current? The answer has to do with electric potential energy. Potential energy is stored energy that an object has due to its position or shape. An electric charge has potential energy because of its position in an electric field. For example, when two negative charges are close together, they have potential energy because they repel each other and have the potential to push apart. If the charges move apart, their potential energy decreases. Electric charges always move spontaneously from a position where they have higher potential energy to a position where their potential energy is lower. This is similar to water falling over a dam from an area of higher to lower potential energy due to gravity. In general, for an electric charge to move from one position to another, there must be a difference in electric potential energy between the two positions. The difference in electric potential energy is called potential difference, or voltage. Voltage is measured in an SI unit called the volt (V). For example, the terminals of the car battery in Figure below have a potential difference of 12 volts. This difference in voltage results in a spontaneous flow of charges, or electric current. Sources of Voltage Batteries are one of several possible sources of voltage needed to produce electric current. Sources of voltage include generators, chemical cells, and solar cells. Generators change the kinetic energy of a spinning turbine to electrical energy in a process called rdp2023 \| G8SHSCIA 53 electromagnetic induction. Chemical and solar cells are devices that change chemical or light energy to electrical energy. You can read about both types of cells and how they work below. Chemical Cells Chemical cells are found in batteries. They produce voltage by means of chemical reactions. A chemical cell has two electrodes, which are strips made of different materials, such as zinc and carbon (see Figure below). The electrodes are suspended in an electrolyte. An electrolyte is a substance containing free ions that can carry electric current. The electrolyte may be either a paste, in which case the cell is called a dry cell, or a liquid, in which case the cell is called a wet cell. Flashlight batteries contain dry cells. Car batteries contain wet cells. Online Activity Watch how batteries work at http://www.youtube.com/watch?v=EJeAuQ7pkpc. The simplest type of battery contains a single cell. The electrodes extend out of the battery for the attachment of wires that carry the current. Both dry and wet cells work the same basic way. The electrodes react chemically with the electrolyte, causing one electrode to give up electrons and the other electrode to accept electrons. In the case of zinc and carbon electrodes, the zinc electrode attracts electrons and becomes negatively charged, while the carbon electrode give up electrons and becomes positively charged. Electrons flow through the electrolyte from the negative to positive electrode. If wires are used to connect the two electrodes at their terminal ends, electric current will flow through the wires and can be used to power a light bulb or other electric device. Solar Cells Solar cells convert the energy in sunlight to electrical energy. They contain a material such as silicon that absorbs light energy and gives off electrons. The electrons flow and create electric current. rdp2023 \| G8SHSCIA 54 Online Activity Figure below and the animation at the URL below show how a solar cell uses light energy to produce electric current and power a light bulb. Many calculators and other devices are also powered by solar cells. Watch the video at http://www.suntreksolar.com/solarElectricity/howCellsWork.asp A solar cell is also called a photovoltaic (PV) cell because it uses light (\"photo-\") to produce voltage (\"- voltaic\"). The contacts in a PV cell are like the terminals in a chemical cell. One contact is negative and the other contact is positive, creating a difference in electric potential, or voltage, which produces electric current. Electric Current and Materials Electric current cannot travel through empty space. It needs a material through which to travel. However, when current travels through a material, the flowing electrons collide with particles of the material, and this creates resistance. Resistance Resistance is opposition to the flow of electric charges that occurs when electric current travels through matter. The SI unit of resistance is the ohm (named for the scientist Georg Ohm). Resistance is caused by electrons in a current bumping into electrons and ions in the matter through which the current is flowing. Resistance is similar to the friction that resists the movement of one surface as it slides over another. Resistance reduces the amount of current that can travel through the material because some of the electrical energy is converted to other forms of energy. For example, when electric current flows through the tungsten wire inside an incandescent light bulb, the tungsten resists the flow of electric rdp2023 \| G8SHSCIA 55 charge, and some of the electrical energy is converted to light and thermal energy. Electric Conductors and Insulators Some materials resist the flow of electric current more or less than other materials do. Materials that have low resistance to electric current are called electric conductors. Many metals--- including copper, aluminum, and steel---are good conductors of electricity. Water that has even a tiny amount of impurities in it is an electric conductor as well. Materials that have high resistance to electric current are called electric insulators. Wood, rubber, and plastic are examples of electric insulators. Dry air is also an electric insulator. You probably know that electric wires are made of metal and coated with rubber or plastic. Now you know why. Metals are good electric conductors, so they offer little resistance and allow most of the current to pass through. Rubber and plastic are good insulators, so they offer a lot of resistance and allow little current to pass through. When more than one material is available for electric current to flow through, the current always travels through the material with the least resistance. That's why all the current passes through a metal wire and none flows through its rubber or plastic coating. Properties that Affect Resistance For a given material, three properties of the material determine how resistant it is to electric current: length, width, and temperature. Consider an electric wire like one of the wires in Figure above. A longer wire has more resistance. Current must travel farther, so there are more chances for it to collide with particles of wire. A wider wire has less resistance. A given amount of current has more room to flow through a wider wire. A cooler wire has less resistance than a warmer wire. Cooler particles have less kinetic energy, so they move more slowly. Current is less likely to collide with slowly moving particles. Materials called superconductors have virtually no resistance when they are cooled to extremely low temperatures. Ohm's Law Voltage, or a difference in electric potential energy, is needed for electric current to flow. As you might have guessed, greater voltage results in more current. Resistance, on the other hand, opposes the flow of electric current, so greater resistance results in less current. These relationships between current, voltage, and resistance were first demonstrated by a German scientist named Georg Ohm in the early 1800s, so they are referred to as Ohm's law. Ohm's law can be represented by the following equation. I = V R Where I is current with the unit amperes or amps(A); V is Voltage with the unit volts (V); and R is Resistance with the unit ohms (Ω). Understanding Ohm's Law You may have a better understanding of Ohm's law if you compare current flowing through a wire from a battery to water flowing through a garden hose from a tap. Increasing voltage is like opening the tap wider. When the tap is opened wider, more water flows through the hose. This is like an increase in current. Stepping on the hose makes it harder for the water to pass through. This is like increasing resistance, which causes less current to flow through a material. Still not sure about the relationship among voltage, current, and resistance? Online Activity Watch the video at this URL: http://www.youtube.com/watch?v=KvVTh3ak5dQ(2:00). rdp2023 \| G8SHSCIA 56 Using Ohm's Law to Calculate Current You can use the equation for current (above) to