Science 8 Lecture Notes 1st Quarter PDF

Science 8 (1st Quarter) Lesson/Week 1: Newton’s First and Second Law of Motion MELC = " Investigate the relationship between the amount of force applied and the mass of the object to the amount of change in the object’s motion." (S8FE-Ia-15) Isaac Newton (The Father of Modern Physics) Born December...

Science 8 (1st Quarter) Lesson/Week 1: Newton’s First and Second Law of Motion MELC = " Investigate the relationship between the amount of force applied and the mass of the object to the amount of change in the object’s motion." (S8FE-Ia-15) Isaac Newton (The Father of Modern Physics) Born December 25, 1642 Died March 20, 1727, London) Sir Isaac Newton, associated with Cambridge University as a physicist and mathematician, became famous after propounding three laws of motion that established a connection between objects and motion. Balanced and Unbalanced Forces: 1) When forces acting on an object are of the same magnitude and opposite in direction, the forces are said to be balanced. The object will remain at rest. 2) When the forces do not have the same magnitude, the forces are unbalanced. An unbalanced force may cause an object to move. First Law: Inertia = states that an object at rest will stay at rest or an object in motion will stay in motion, unless an external force acts on it. Force = a push or pull f = force (ma) Nf = normal force Af = applied force Gf = gravity force (9.8 m/s2) Second Law: Acceleration = states that when a constant force acts on an object or body, it causes it to accelerate. Newton = unit of measurement 1N = 1kg per m/s2 f = force (ma) m = mass (kg) Gf = gravity force (9.8 m/s2) a = acceleration (f/m) SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 1 Activity 3: Observe the illustration... 1. Find out which side is stronger. How? 2. You can do this with pulling a table with one hand, then 2 hands. What happened? SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 2 Science 8 (1st Quarter) Lesson/Week 2: Newton’s Third Law of Motion MELC = " Infer that when a body exerts a force on another, an equal amount of force is exerted back on it.” (S8FE-Ia-16) Third Law: Interaction (Action-Reaction) = states that “for every action there is an equal and opposite reaction.” Forces always exist in pairs. Whenever two objects interact, they exert a force on each other. Formula: F1=F2 (Force 1 is equals to Force 2) Question and Answer: Act.#2 Get a chair then sit.... 1. What force that keeps you on the ground/floor? 2. What is keeping you from falling to the ground/floor right now then? How? 3. Consider if you put something very heavy in the chair such as a 100-kg of metal. What may happen? Justify your answer? Activity (Letter G, Activity #3) Action-Reaction (Paper Bullet) 1. Get a ¼ sheet of paper, fold it into 5. 2. Use a wooden or steel ruler to measure Newton. 3. Place your “paper bullet” on the rubber band. 5. Pull paper and then release. 6. Do the procedure three times with different amount of forces. Record your observations. RUBRICS: Timeliness (5) Quality (5) Lesson (5) 5 Submitted before 5 Research, arts, essay 5 Relevant, reflection 4 Submitted during 4 Completed answers 4 Relevant 3 Submitted after 3 No effort, limited 3 Limited relevance 2 Forced or did not 2 Forced or did not 2 No relevance SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 3 Science 8 (1st Quarter) Lesson/Week 3: Potential and Kinetic Energy MELC = " Identify and explain the factors that affect potential and kinetic energy.” (S8FE-Ia-15) Energy = the ability or capacity to do work. Joule (J) = unit of measurement (SI system). I. Potential Energy = object at rest. Formula: PE=mgh (answer is always zero) m=kilograms (kg) Fg=force of gravity (9.8 m/s2) h=height in meters (m)...When the man exerted force in lifting the box, he loses energy. Work is done on the box, and the box gains energy. II. Kinetic Energy = object at motion. Greek word “kinetikos” which means moving. Formula: KE = ½ mv2 m=kilograms (kg) v=velocity or speed (m/s) KE=50kg x 10m/s KE=50kg x 10m/s KE=500 2 KE=250J Activity (Letter G, Activity #4) Draw an arrow on the diagram that represents the direction of the force of the objects. SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 4 Science 8 (1st Quarter) Lesson/Week 4: Sound and Temperature MELC = "Investigate the effect of temperature to the speed of sound." (S8FE-Ia-15) Sound = a type of energy that vibrates and travels through air. Speed of sound: 1) 331 m/s in dry air at 0 Celsius (1,234 kph) 2) Speed increases by 0.6 m/s every 1 C Reflection = the turning back of the wave as it hits a barrier (echo). Formula: v = velocity (speed and direction) T = temperature m/s = meter per second (speed) C = Celsius SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 5 Activity (Letter G, Activity #4A) ESSAY OBSERVATION (on notebook): 1. Why do you hear the siren sound of a fire truck clearly in a nearby barangay during nighttime than daytime? 2. Why is it quieter in areas with high elevation such as Tagaytay and Baguio than in lowlands? Activity (Letter G, Activity #4B) Let’s Make a Telephone!!! (Per Group) What we need: 2 plastic or paper cups 3 meters string (leteng) or yarn 2 paper clips Challenge: Pass the secret message! SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 6 Science 8 (1st Quarter) Lesson/Week 5: Hierarchy of Colors and Energy of Visible Light MELC = " Explain the hierarchy of colors in relation to the energy of visible light." (S8FE-If-27) What is light? A kind of energy that can travel through space in a form of wave. Light looks white, but really is a mixture of many colors. Dispersion = a kind of refraction which provided us colors of light. This phenomenon is observed when white light passes through a prism. It breaks white light into constituent colors namely: red, orange, yellow, green, blue, indigo, and violet (ROYGBIV). Prism = a transparent optical element made of glass, plastic, fluorite (mineral form of calcium fluoride CaF2) with flat and polished surfaces that disperses light. Water in a glass can also act as prism. Refraction = the bending of light when it travels from one medium to another. An example of refraction is when a ray of light passes through a glass block Violet has the highest frequency, energy, and is the one that is bent the most. At the end of the spectrum, red has the lowest frequency, energy, and is bent the least. * (nm=nanometers ; THz=terahertz ; eV=electron volt) SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 7 Blue Sky and Red Sky Black Color VS. White Color  Black absorbs all light.  Black converts light into heat.  Black do no reflect any color. SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 8 Science 8 (1st Quarter) Lesson/Week 6: Hierarchy of Colors and Energy of Visible Light MELC = "Differentiate between heat and temperature at the molecular level." (S8FE-If-29) What is Heat?  Energy transferred from one body to another due to change in temp.  Heat naturally moves from an object with high temperature to an object with low.  Heat formula: q=mcΔT (quantity of heat) q=heat in joules (J) or calories (cal). m=mass c=specific heat in J ΔT=change in temp  Objects do not contain heat, but contain thermal energy.  Thermal Energy (internal heat energy) is produced when a rise in temperature causes atoms and molecules to move faster and collide.  Ice hurts, why? (Heat energy is released) Temperature = the amount of energy present in an object due to the motion of its particles or molecules.  Our bodies’ normal temp is 370 Celsius.  At 37.50C, germs, viruses, and bacteria die. Weakness, body pain, runny nose, and no appetite. Thermal Expansion = happens when the internal energy of a substance increases, causing the particles to spread out expanding the mass.  When an object is cooled, it contracts. Thermoscope = device that shows changes in temperature with expansion of air. Phase Change = when an object absorbs or takes in heat or releases or gives off heat, its phase also changes. SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 9 Activity (Letter G, Activity #4) 1. Why do we get a fever? 2. If our normal body temperature is 370 Celsius, what temperature starts a fever? 3. List down symptoms of a fever? a. W______________ b. B______ P_______ c. R______ N_______ d. No A___________ 4. Why do we experience these symptoms? SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 10 Science 8 (1st Quarter) Lesson/Week 7: Current and Voltage MELC = " Infer the relationship between current and voltage." (No CODE in PDF MELC) What is Electricity? The phenomenon associated with stationary or pushing electric charges (electrons).  Electric charges can be made to move through a conducting material. The electric charges are the electrons of the conducting materials.  Materials such as copper, steel, and aluminum have a lot of loosely held electrons which made them good conductors of electricity.  Similarity between thermal and conductivity. What is Current? = (I) measure of the number of charges passing through a cross-section of a conductor in a given time. Measured by ampere (A). What is the direction of current? A battery has terminal marks “+”and “-“. The plus (+) sign indicates surplus or excess of charge and the negative (-) sign means deficiency. The movement of charges from the negative side of the battery to the positive side is called conventional current or simply current. Ammeter = measures electric current. Ampere = unit of measure of the rate of electron flow or current in an electrical conductor. Voltage = (V) the pressure from an electrical circuit's power source that pushes charged electrons (current) through a conducting loop. Measured by voltage. We have 220 Volts Voltmeter = measures voltage. Resistance = (R) a measure of the opposition to current flow in an electrical circuit. Measured by ohm (Ω).  The resistance of an object also changes when the object becomes wet. Dry human skin for instance has a resistance of 100,000 ohms but when it gets wet its resistance is reduced to 1,000 ohms. That is why it is important to dry the hands when plugging electrical appliances. SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 11  What’s the problem here? Activity 4: PERFORMANCE TASK (15 points): Using the materials provided: Battery, wires, and led or bulb... 1. How is light produced? 2. How do a battery give energy? 3. What is the most efficient way to light the led? (sketch or draw your electrical diagram) SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 12 Science 8 (1st Quarter) Lesson/Week 8: Advantages and Disadvantages of Series and Parallel Connections MELC = "Explain the advantages and disadvantages of series and parallel connections in homes." (S8FE-li-31) What is a Circuit? An electrical network by interconnection of electrical components like light and appliances. Properties of a Series Circuit  A circuit that consists of one loop.  Total resistance is always greater than the individual resistances in a series circuit.  The voltage source is equal to the sum of all voltage in each load in a circuit.  The current is constant across each load. Advantages of Using Series: 1. A series connection does not overheat easily. For a given circuit of two loads, the amount of current passing through each load is constant. 2. In a series circuit, there is the only one path For the current to flow from the source to different loads. Easy to connect/disconnect new load. 3. Since series circuit is less likely to overheat, there is no need to use expensive, thick wires. Disadvantages of Using Series: 1. If one of the light bulbs is damaged or removed in a series connection, other bulbs in the circuit will not light because of discontinue of flow. 2. The addition of more light bulbs in series circuit causes a decrease in the brightness of the bulbs because there’s a sharing of energy. 3. The loads are difficult to control individually. When switch is off, all loads will not function. 4. It is difficult to identify the damaged bulb in series. Properties of a Parallel Circuit  Circuit has two or more loops.  Total resistance is always less than the smallest resistance.  There is only one voltage which is equal to a voltage source.  The total current is equal to the sum of all currents in each load in a parallel circuit. Advantages of Using Parallel: 1. All loads in parallel are directly connected to the voltage. Even with resistances, all light bulbs can still have their maximum brightness. 2. If a bulb is damaged, all other light bulbs will still function. Therefore, it’s reliable. 3. Individual load is easy to control. Each load has a connecting wire or switch. 4. All light bulbs and appliances at home are connected in parallel. Disadvantages of Using Parallel: 1. Overloading/overheating may happen if appliances are simultaneously used at home since total resistance decreases. 2. A parallel connection is difficult to install, maintain, and repair since large volume of conducting wires is needed. 3. It requires the use of several conducting wires of varying sizes. SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 13 Activity (Letter G, Activity 4) PERFORMANCE TASK(15 points): Draw a diagram of you house or your dream house and design the electrical wirings. OPTIONAL: 1. Use Red color for live or positive. 2. Use Black color for neutral or negative. SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 14 Science 8 (1st Quarter) Lesson/Week 9: Functions of Circuit Breakers, Fuses, Earthing, Double Insulation, and other Safety Devices at Home MELC = "Explain the functions of circuit breakers, fuses, earthing, double insulation, and other safety devices in the home.." (S8FE-li-33) What is Electrical Hazard? Electrical hazard or electric shock is a condition due to direct or indirect electrical contact which a person may sustain injury.  Current does the damage, and not the voltage (60Hz). What is an Arc Flash? = or arc blast, a phenomenon where a flashover of electric current leaves its intended path and travels through the air. The Fatal (Deadly) Current 1. It can cause malfunction of the brain and heart. May lead to cardiac arrest or death. 2. The body will experience intense heat that can cause skin burning. 3. Muscles will involuntarily contract which will be hard to control. Safety Practices 1. The practice of using only one hand (keeping one hand behind your back). 2. Disconnect all sources of power if you are to repair. 3. Do not rely on insulated tool handles, rubber-soled shoes, etc., to protect you. 4. It’s better to shut down the main switch or general switch before doing repairs. What are the Types of Hazards? 1. Faulty Electrical Wiring = one leading cause of fire. Inadequate wiring, exposed electrical parts, wires with bad insulation, fuses blow or circuit breakers trip frequently. 2. Short Circuit = circuit condition in which a current takes the path of less resistance or zero resistance.  Where V = I R I = 𝑉𝑅 when R = Ø I = approaches infinity. Octopus Wiring 3. Grounded Circuit = fault occurs when electricity takes an unplanned path to a its metal casing or the ground. Electrical Safety Devices/Measures: 1. Circuit Breaker = uses electromagnets and bimetallic strips to shutdown a switch in cases of overloading. Cannot be turned on unless the short circuit is fixed. 2. Fuse = made up of metal ribbon that heats up and melt if current exceeds its rating protecting the appliance. 3. Automatic Voltage Regulator (AVR) = a device designed to protect appliances by regulating voltage. 4. Uninterruptible Power Supply (UPS) = provides emergency power to the load when there is unexpected power disruption. Also functions like an AVR. SCIENCE 8 Lecture, OGLE “SIR NUBE” MARIN... Page 15 5. Earthing or Grounding = a system of connecting the metal casing of the appliance to earth to dissipate excess current. 6. Double Insulation = a safety measure done by appliance manufacturers to prevent electric shock and grounded external casing of appliances, eliminating the need for earthing. Activity (Letter G, Activity 4) PERFORMANCE TASK (15 points): On a 1 whole sheet of paper, study the picture and answer the questions that follow: 1. Is the conducting wire safe to be used at home? Why? 2. Suggest ways on how to keep your family members safe from the electrical hazard. 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