Chapter 4 Glossary PDF

CHAPTER 3 Glossary incomplete combustion: radiation sickness: a condition that results from a combustion that occurs when large dose of ionising radiation, causing significant oxygen is limited; produces...

CHAPTER 3 Glossary incomplete combustion: radiation sickness: a condition that results from a combustion that occurs when large dose of ionising radiation, causing significant oxygen is limited; produces cell death; symptoms include nausea, vomiting, fever, carbon (soot, smoke) and hair loss and diarrhoea carbon monoxide, and does not radioactive: emitting radiation release as much heat or light as radioisotope: an isotope with a nucleus that may complete combustion incomplete combustion undergo a nuclear reaction ionising radiation: any form radiotherapy: a cancer treatment in which tumours of radiation that has the ability to remove electrons are exposed to high concentrations of radiation from atoms and molecules reactants: chemicals that take part in a chemical isotopes: atoms that have the same number of reaction; they are written on the left-hand side of the protons but a different number of neutrons arrow law of conservation of mass: atoms are not created respiration: a series of chemical reactions that or destroyed in a chemical reaction; they can only be releases energy from glucose; it takes place in the rearranged mitochondria inside cells mitochondria: organelles in rust: hydrated iron(III) oxide; chemical formula plant and animal cells where Fe2O3.H2O respiration takes place salt: the term commonly used for sodium chloride, mutation: a change in the but which covers any compound formed by a metal DNA of a cell that causes it taking the place of the hydrogen atom in an acid to change how it works and mutation stable nuclei: nuclei that will never undergo a reproduces nuclear reaction neutralisation: a reaction of an stomata: microscopic holes in the leaves of plants acid with a base, forming a salt and where gases such as oxygen, carbon dioxide and water water vapour can enter or exit the plant nuclear decay: when a nucleus tarnish: a black coating of silver sulfide that is undergoes a nuclear reaction and produced when silver reacts with sulfur in food or emits radiation neutralisation the atmosphere; chemical formula Ag2S nuclear radiation: rays or particles transmutation: a nuclear that are emitted by a nucleus during reaction that converts one proton a nuclear reaction type of atom into a different Na Ne nuclear reaction: a process that causes a nucleus to type of atom change, including alpha decay, beta decay, fission transmutation unstable nuclei: nuclei that and fusion may undergo a nuclear reaction at any time photosynthesis: endothermic reaction that takes verdigris: a green coating of copper hydroxide that is place in green plants; uses energy from sunlight to produced when copper reacts with moisture, carbon combine water and carbon dioxide and produce dioxide and oxygen in the atmosphere; chemical glucose and oxygen gas formula Cu(OH)2 products: chemicals produced in a word equation: simple written description of what is chemical reaction; they are written happening in a reaction on the right-hand side of the arrow radiation burns: redness and blistering on the surface of the skin or other organs caused by intense exposure to ionising radiation radiation burns AB 3.11 CHAPTER 3 REACTION TYPES 123 4 CHAPTER Heat, sound and light Have you ever wondered... why a doona keeps you warmer than just a sheet? why tiles feel colder than carpet? how musical instruments make different sounds? why you cannot see clearly underwater? LightbookStarter why diamonds sparkle? LS LS After completing this chapter you should be able to: discuss how the wave and particle models explain how energy is transferred outline how energy moves differently, depending on the material it passes through investigate the transfer of heat through convection, conduction and radiation use the particle model to explain conduction and convection identify safe sound levels for humans and how this affects leisure and the workplace. This is an extract from the Australian Curriculum AB 4.1 Victorian Curriculum F–10 © VCAA (2016); reproduced by permission 124  MODULE 4.1 Heat In cold weather, you seek extra jumpers or thicker doonas to keep warm. When it is really hot, you wear less clothing and cool yourself with a fan or by jumping in the pool. Heat is a form of energy that you sense through receptors in your skin. Heat is lost from your skin as you stand in front of a fan and is gained as your body absorbs radiant heat from the flames of a log fire. science 4 fun Burning a balloon! Can you heat water in a balloon without NO 4 Now hold another balloon bursting the balloon? under a tap and fill it up with Collect this … water to about the size of a rockmelon. two balloons matches 5 Place a lit candle underneath this second balloon, and candle again observe what happens. Do this … Record this … 1 Blow up a balloon and tie its end. 1 Describe what happened. 2 Hold a lit candle below the balloon. 2 Explain why you think this happened. 3 Observe what happens. The particle model The particles of a gas are not bound together at all and are free to move in straight lines until they collide Heat is a form of energy that can be transferred with other gas particles, or the walls of the container through solids, liquids and gases. To understand how in which they are held. Particle model diagrams for a this happens, you first need to understand the particle solid, a liquid and a gas are shown in Figure 4.1.1. model of matter. In the particle model, atoms are considered as small, hard balls. In a solid, the particles are closely packed. The particles vibrate on the spot but keep the shape of the substance they form. Particles in a liquid are packed closely together too. The particles vibrate but are also free to move or flow over each other. solid liquid gas FIGURE 4.1.1 Particle model diagrams for a solid, a liquid and a gas CHAPTER 4 HEAT, SOUND AND LIGHT 125  Heating substances Temperature Heating a substance adds energy to its particles. Some Temperature can be measured using a thermometer. of this energy is stored in the material itself as potential A thermometer contains a liquid (alcohol or mercury) energy. The remaining heat energy increases the kinetic inside a narrow glass tube. This liquid expands when energy of the particles in the material. Kinetic energy heated and contracts when cooled. Temperature is read is the energy of movement. So if the temperature of from a scale on the thermometer corresponding to the a substance increases, then its particles move faster expansion or contraction of the liquid. Temperature is and faster. This spreads the particles further apart and commonly measured in degrees Celsius (°C). the substance expands. Similarly, particles lose kinetic The Fahrenheit (°F) and kelvin (K) scales are also used energy when the temperature decreases. The particles to measure temperature. The three scales are compared slow down and the substance contracts. Figures 4.1.2 in Figure 4.1.4. and 4.1.3 show what happens when a solid and a gas is heated or cooled. boiling point of When sufficient heat energy is added to a solid or a water 212°F 100°C 373 K liquid, the particles break free from each other and the substance changes state and melts or evaporates. freezing point of water 32°F 0°C 273 K absolute zero –459°F –273°C 0K Fahrenheit Celsius Kelvin scale scale scale FIGURE 4.1.4 The three scales commonly used to measure temperature hot expansion contraction FIGURE 4.1.2 The particles in a solid vibrate more when heated. This causes the cold solid to expand. hot expansion FIGURE 4.1.3 The particles of a gas travel contraction faster when heated. They hit the sides of the container more frequently and with more cold force. A balloon has flexible walls so this force will cause it to expand. 126 PEARSON SCIENCE 9 2ND EDITION The temperature of a substance is a measure of the average kinetic energy of its particles. The particles Heat flows from the warmer hands into of hotter substances move faster than the particles of the ice. cooler substances. As the temperature drops, particles lose kinetic energy. Eventually the particles barely move at all. This happens at –273°C, at a point called absolute zero. Thermometers measure temperature but do not measure the heat of a substance. Heat is a form of energy and is a way of describing the total energy of all particles within an object. For example, saucepans A and B in Figure 4.1.5 both contain boiling water. Their temperatures are equal. However, saucepan B contains Heat flows from twice the volume of water and so it has twice the heat the hotter cup into the hands. energy of saucepan A. Saucepan A 100°C fewer particles less energy overall FIGURE 4.1.6 Heat flows from your hands into an ice block, Saucepan B and from a hot cup into your hands. 100°C Hotter substances have faster moving particles more particles than particles in cooler substances. For example, more energy overall the particles in a cup of hot coffee vibrate rapidly because of its temperature. If a metal spoon is put into the coffee, then the particles of the spoon vibrate FIGURE 4.1.5 The amount of boiling water in saucepan B is faster too. This spreads the heat through the spoon twice that in saucepan A. For this reason, saucepan B has twice and increases the temperature of the spoon, making the energy. it hot to touch.This process of heat transfer by vibrating particles is called conduction and is shown Heat transfer in Figure 4.1.7. Heat flows from areas of higher temperature to areas of lower temperature. The greater the temperature difference, the faster the flow of heat from one object to another. This process of heat transfer can happen in Vibrations pass energy on. three ways: conduction, convection and radiation. Conduction Hold an ice block and your hands get cold. This is because heat flows from your skin into the ice, lowering the temperature of your skin in the process.You know that Heat is conducted in this direction. the ice cube is absorbing this heat because it starts to melt. Heat has flowed from a high temperature (your hands) to a lower temperature (the ice block). This is shown in Figure 4.1.6. Likewise, when you grip a hot cup, FIGURE 4.1.7 Particles near the flame vibrate more as they heat flows from the cup into your hands warming them absorb heat energy. These vibrations transfer energy to conduct heat along the solid. up—the cup is at a higher temperature than your hands. CHAPTER 4 HEAT, SOUND AND LIGHT 127  Conductors Some materials conduct heat well while others do not conduct heat at all. A glass of ice-cold lemonade feels much colder than a polystyrene cup of ice‑cold lemonade. This is because glass is a better heat conductor than polystyrene. As a result, heat flows from your warm hand into the cooler glass and your hand feels cold. When holding the polystyrene cup, your hand is not losing heat and so it still feels warm. Substances that transfer heat easily are known as conductors. Metals are good conductors of heat. This is why most saucepans are made of stainless steel FIGURE 4.1.9 Wool fibres and the fluffy polyester, down or (Figure 4.1.8). Silver, gold, aluminium and copper cotton filling inside a ski parka trap air and help prevent heat loss from your body. are particularly good conductors of heat. Sometimes, saucepans have a copper base to better conduct heat. FIGURE 4.1.8 Metals are good conductors of heat. FIGURE 4.1.10 These animals must stay warm in very cold conditions. Insulators Polar bears rely on body fat and a thick coat of fur for insulation, Plastic, air, cloth, cork, wood and rubber are all very and penguins have layers of fat and poor conductors of heat, and sometimes can block feathers that they can fluff up to trap heat transfer completely. Such substances are known more air. as insulators. The handles of a saucepan are usually made from insulating materials to allow you to lift them without burning your hands. An Esky uses insulators such as polystyrene to keep food and drinks cool. SciFile Gases are poor conductors of heat. Air trapped by Penguins master the cold woollen jumpers and blankets helps to insulate your Penguins live in some of the coldest conditions body from losing heat. Ski parkas, doonas and sleeping on Earth. They huddle together during storms bags are filled with cotton, feathers, wool and polyester to minimise the surface area of the flock and to that also traps air and helps to protect you from the minimise the heat loss through conduction to the cold (Figure 4.1.9). Similarly, animals like penguins cold air around them. Most of a penguin’s heat and polar bears that live in cold climates have should conduct to the ice they stand on, but heat adaptations that help them stay instead conducts from hot blood flowing through arteries passing down their legs to the cold blood warm (Figure 4.1.10). Prac 1 Prac 2 AB p. 134 p. 135 4.2 flowing through veins returning from their feet. 128 PEARSON SCIENCE 9 2ND EDITION Convection Convection explains the formation of a sea breeze during the day and a breeze towards the sea at night. As air is heated, its particles gain energy and move This process is shown in Figure 4.1.13. Convection also further apart. This hot air is less dense than cool air, circulates heat in a hot water system.You can see this in and so it is pushed upwards by cooler air around it. Figure 4.1.14. This method of heat transfer is called convection. The air flow it creates is called a convection current. Such a current is shown in Figure 4.1.11, transferring heat from an open fire. warm air air cools rises and drops insulated ceiling cool air rushes in to fill space Warm air is Air cools left by warm air pushed upwards. and sinks. warmer land cooler sea A sea breeze during the day Fire warms air. Cooler air flows in. air cools warm air and drops rises cool air rushes in to fill space FIGURE 4.1.11 Convection currents gradually spread heat from left by warm air the open fire through the air in a room. Heat is transferred by convection in liquids and gases because their particles can move around. Figure cooler land warmer sea 4.1.12 shows how liquid in a saucepan is heated by A land breeze at night convection. Convection cannot happen in a solid FIGURE 4.1.13 In the daytime, land heats up more quickly because the particles can only vibrate and cannot move than the sea. Hot air is pushed upwards by cooler air that flows freely like they do in a liquid or gas. in towards it, producing a sea breeze. At night, the sea stays warmer for longer than the land and the process is reversed to Water heats by convection. produce a land breeze. Saucepan heats to hot taps by conduction. hot water rises convection current FIGURE 4.1.12 Particles gain heat from the hot base of the saucepan and rise. Cooler liquid sinks down, is heated and the cycle continues. cold water sinks cold water boiler FIGURE 4.1.14 Convection assists in circulation of water in a hot water system. CHAPTER 4 HEAT, SOUND AND LIGHT 129  science 4 fun SciFile Ups and downs! Feeling chilly? Naked mole rats are the only mammals known Can you see convection currents in NO to not control their body temperature. Their action? bodies are warmed to the temperature of their Collect this … burrows, about 30°C. dried beans, such as borlotti beans or chickpeas Bunsen burner, gauze mat, tripod and bench mat large beaker of water Do this … 1 Add dried beans to cover the base of the beaker. 2 Cover the beans with water and then heat the mixture carefully over a Bunsen burner. 3 Turn off the heat after you have observed the behaviour of the beans in the hot water. Record this … 1 Describe what happened. 2 Explain why you think this happened. beaker water beans gauze FIGURE 4.1.15 Radiation from the Sun travels through the mat vacuum of space to reach us. It is cooler in the shade because tripod place this radiation has been blocked. Bunsen burner The hotter something is, the more heat it radiates. For off-centre example, a hot oven radiates more heat than an oven bench mat set at a lower temperature. Similarly, the red-hot coals of an open fire radiate such enormous amounts of heat that you cannot sit too close to them (Figure 4.1.16). Radiation When you go outside and into the sunlight, you can feel the heat from the Sun on your skin (Figure 4.1.15). Heat has travelled through empty space between the Sun and the Earth to reach you. It cannot be transferred by conduction or convection on its journey because there are no particles to vibrate or flow in the vacuum of space. The Sun transfers its heat energy through a process called radiation. FIGURE 4.1.16 You can feel the radiant heat emitted from the Radiation transmits heat as invisible waves that travel glowing coals of an open fire. at the speed of light, which is around 300 000 km/s. Infrared radiation is heat energy that is transmitted When radiated energy hits a surface, the heat may this way. All objects emit (release) some infrared be absorbed into the surface, reflected from the radiation. surface or transmitted through the surface. 130 PEARSON SCIENCE 9 2ND EDITION This is shown in Figure 4.1.17. Often radiation will be partially absorbed, reflected or transmitted according to SciFile the material and its colour. Home insulation Dark colours Light colours Clear materials, such absorb reflect radiated as glass, transmit Heat transfer in a home occurs by conduction, radiated heat. heat. radiated heat. convection and radiation. In winter, warm air flows out of the house, and in summer, warm air flows in. Insulation added to the ceiling and walls of a home helps to stop this transfer of heat and makes your home more energy efficient. absorption reflection transmission FIGURE 4.1.17 When radiation hits an object, it may be absorbed, reflected or transmitted. For example, a dark-coloured car heats up more quickly in sunlight than a lighter-coloured car. This happens because dark-coloured objects absorb most of the radiation that fall on them. This means that they STEM 4 fun absorb much of the heat falling on them from the Sun. Insulated ice cube Solar pool heaters and hot solar hot water systems use PROBLEM black tubes and collection panels to absorb as much How long can you keep an ice cube frozen? radiant heat from the Sun as possible (Figure 4.1.18). Lighter coloured objects reflect much of the radiation SUPPLIES frozen ice cube falling on them—most of the heat that plastic cup falls on them is reflected and so they Prac 3 AB p. 136 4.3 assortment of items as possible insulation don’t heat up as rapidly. materials including cotton balls, polystyrene, aluminium foil, rags, petroleum jelly, etc. PLAN AND DESIGN Design the solution: what to hot water information do you need to solve the problem? taps radiation Draw a diagram. Make a list of materials you from Sun will need and steps you will take. CREATE Follow your plan. Draw your solution to the problem. IMPROVE What works? What doesn’t? How do you know it solves the problem? What could work better? Modify your design to make it cold better. Test it out. water roof REFLECTION 1 What field of science did you work in today? Are there other fields where this activity applies? 2 In what career do these activities connect? 3 What did you do today that worked well? FIGURE 4.1.18 Heat energy radiated by the Sun is absorbed by What didn’t work well? the cold water within the black collection panels of a solar hot water system. CHAPTER 4 HEAT, SOUND AND LIGHT 131  LightbookStarter MODULE 4.1 Review questions LS LS Remembering 9 You lose a lot of heat from your head. For most people, their hair protects them from losing 1 Define the terms: too much heat from their heads. Why is hair an a temperature b conduction effective insulator? c insulator. 10 You walk barefoot on carpet in the living room 2 What term best describes each of the following? of your house and your feet feel warm, yet when a the temperature at which particles barely you walk into the bathroom and stand on the move at all ceramic tiles your feet feel cold. The carpet and b heat transfer involving particles that are free tiles are at the same temperature. Explain why to move the carpet and the tiles feel so different. c cool air that flows from above a body of water towards land during the daytime. Applying 11 Use the particle model to explain why the 3 What is the temperature that water freezes on the following expand when heated. following scales? a a solid metal rod a Fahrenheit  b Celsius  c kelvin. b a balloon. 4 Fill in the following statements with the term that makes them true. 12 Heat transfer can occur by conduction, a Heat always flows from an object of higher/ convection or radiation. Identify the main lower temperature to one of lower/higher method of heat transfer in each situation below. temperature. a Your feet get hot when you walk on sand at the beach. b Insulators are good/poor conductors of heat. b Your back feels warm when you sit in the sun. c Gases are good/poor conductors of heat. c You boil water in an electric kettle. d On a warm day, a house is warmer upstairs because of conduction/convection currents. d You feel cold when you dive into a swimming pool. 5 In the science4fun on page 130, the beans moved e You feel warm air as you walk into a school about the beaker because of the transfer of heat. disco held in a hall. Was the heat transfer an example of conduction, convection or radiation? Analysing Understanding 13 What is the difference between heat and temperature? 6 Group the following objects as either conductors of heat or insulators. 14 Two identical bathtubs are filled to the same level a a gold wedding ring with water. The particles in bathtub A move with b a polystyrene cup greater speed than the particles in bathtub B. Analyse this situation to answer the following. c a metal seatbelt buckle a Which bathtub will have warmer water? d an aluminium fence b Which bathtub will have more heat energy? e thermal underwear. c As the water cools, each bath loses heat 7 Describe how the motion of particles in a solid energy. List three places this heat energy change as the solid is heated. could go. 8 A wetsuit traps a thin layer of water between the wearer and the neoprene fabric of the suit. a State whether water is a good or poor conductor of heat. b How does the wetsuit keep the wearer warm? 132 PEARSON SCIENCE 9 2ND EDITION  MODULE 4.1 Review questions 15 Water absorbs a large amount of heat energy for 19 Sonja and Marcos are testing the insulating a relatively small rise in temperature compared to properties of cup A and cup B in their science other substances. Use this information to analyse laboratory. After testing, they plot the graph why in the science4fun on page 125 the balloon shown in Figure 4.1.20. does not burn when filled with water. Cooling of cups A and B 90 Evaluating 80 Temperature (degrees celsius) 16 On a hot day, you have a choice of travelling in a 70 red car, a white car or a black car, all of the same 60 model. All have been parked in the sunlight for three hours. 50 a Which car would you choose? 40 Temperature cup A b Justify your choice. 30 Temperature cup B 17 Pyrex glass expands less than ordinary glass 20 when heated. Use this information to propose a 10 reason why Pyrex is used in cooking instead of 0 ordinary glass. 0 1 2 3 4 5 6 7 8 9 10 Time (minutes) 18 Figure 4.1.19 shows the experimental FIGURE 4.1.20 set-up for a radiation experiment. The same-sized black and white cardboard squares a What procedure do you think the students are attached to two thermometers close to an used in their experiment? incandescent globe. b What is the independent variable being a What do you think the student is trying to tested? test in this experiment? c What is the dependent variable that Sonja b State three variables that must be controlled and Marcos are measuring in this task? to ensure a fair test. d To be a fair test, which variables would c Predict which thermometer will show the Sonja and Marcos need to control in this highest reading after 5 minutes. experiment? d Discuss reasons for your answer to part c. e What is the initial temperature of the contents of cup A and cup B? f Describe how the temperature of this liquid varied over the 10 minutes in cup A and cup B. g Assess which cup is the better insulator. Creating 20 Create a short story in which you imagine that you are one of the beans that was heated in the science4fun on page 130. Describe how your temperature and movement change as the beaker is heated. For at least four stages of your motion, add illustrations showing where you are FIGURE 4.1.19 positioned inside the beaker. 21 a  onstruct a diagram of a new type of suit C that will keep you warm in cold conditions. b On your diagram, label what the suit is made from and how it keeps the heat in. CHAPTER 4 HEAT, SOUND AND LIGHT 133  MODULE 4.1 Practical investigations 1 Comparing materials metal icy-pole spoon Purpose plastic stick To compare how well plastic, wood and metal spoon conduct heat. Hypothesis Which do you think will conduct heat better—a plastic spoon, a wooden stick or a metal spoon? Before you go any further with this investigation, write a hypothesis in your workbook. Timing 30 minutes hot water Materials butter SAFETY very hot water (from a kettle) Handle hot water FIGURE 4.1.21 with care. plastic spoon metal spoon Results wooden icy-pole stick Record all results in your results table. 250 mL beaker Time taken to drop (seconds) small beads or similar stopwatch Bead on Bead on Bead on ruler plastic spoon icy-pole stick metal spoon Procedure 1 In your workbook, construct a results table like Review the one in the Results section. 1 Which of the materials used was the best 2 Put a dob of butter near the top of the handle of conductor of heat? the plastic spoon. 2 Assess whether or not your hypothesis was 3 Push a bead onto the dob of butter. correct. 4 Repeat steps 1 and 2 for the metal spoon and 3 Which material was the best insulator? icy-pole stick. Make sure the beads are placed at 4 Explain why it was important to place the beads equal heights and that the same amount of butter at the same height, and use the same amount of is used each time. butter. 5 Carefully place the spoons and the icy-pole stick 5 The thermal conductivity of a material is a into very hot water in the beaker as shown in measure of how well the material conducts heat. Figure 4.1.21. It has the unit watts per metre kelvin (W/m/K). 6 Time how long each bead takes to fall off, and The higher this value is, the better the substance record your results in a table like the one shown conducts heat. in the Results section. Use your results to identify which of the following thermal conductivities belong to the plastic spoon, the metal spoon and the wood icy-pole stick. 0.17 16.0 0.19 134 PEARSON SCIENCE 9 2ND EDITION  MODULE 4.1 Practical investigations 2 Testing insulators 2 Carefully measure 200 mL of hot water using a beaker, and pour this into your can. Purpose 3 Place the can inside the box. To test how effective different materials are in 4 Record the initial (starting) temperature of insulating heat. the water, and then measure and record the Hypothesis temperature every 2 minutes for 10 minutes. Which of the materials that you have available Record all your measurements in a table like that for this prac do you think will keep water in a can shown below. the warmest? Before you go any further with this 5 Repeat, using water at the same initial investigation, write a hypothesis in your workbook. temperature and packing one of the insulating Timing 60 minutes materials into the space between the can and the box, as shown in Figure 4.1.22. Materials 6 Repeat the process, using a second insulating a range of insulating materials, such as newspaper strips, cloth, cotton wool, foam, polystyrene material. beads, foam packing bullets, fibreglass insulation, carpet scraps aluminium can thermometer with 200 mL water insulating thermometer or material temperature probe SAFETY cardboard box cardboard box Handle hot water hot water with care. beaker stopwatch or clock empty soft-drink cans FIGURE 4.1.22 You may use a temperature probe to gather temperature data. Procedure Results 1 In your workbook, construct a table like 1 In your results table, insert the names of two that shown below. Alternatively, construct a insulating materials you are going to test. spreadsheet with similar columns to those in 2 Record all measurements in your table or the table. spreadsheet. 3 Construct a line graph of temperature versus time for each sample tested, to show the Water temperature temperature drop over time. Alternatively, use Time Water temperature (°C) data-logging equipment to produce a graph. (minutes) Can with no Can with Can with Review insulating insulating insulating materials (air only) material A material B 1 a Construct a conclusion about which material was the best insulator. 0 b Assess whether your hypothesis was 2 supported or not. 4 2 Why was it important to test one can with no 6 insulating materials? 3 Identify any sources of error in your experiment. 8 4 Outline any improvements that could be made to 10 the design of the experiment. CHAPTER 4 HEAT, SOUND AND LIGHT 135  MODULE 4.1 Practical investigations STUDENT DESIGN 3 Comparing heat radiation Purpose Hints To compare how silver, white and black cans radiate Make sure: heat. your cans all contain the same amount of water Hypothesis the water is at the same starting temperature. Which colour aluminium can do you think will Use the STEM and SDI template in your eBook radiate more heat over time—silver, white or black? to help you plan and carry out your investigation. Before you go any further with this investigation, write a hypothesis in your workbook. Results Timing 45 minutes 1 Write a report on your findings. Materials 2 Construct a line graph to display your results. SAFETY Review silver, white and black aluminium cans A risk assessment 1 Evaluate your procedure. Pick two other prac is required for this thermometer or investigation. groups and evaluate their procedures too, temperature probe Be careful when identifying their strengths and weaknesses. handling hot liquids. 2 a Construct a conclusion for your Procedure investigation. 1 Design an investigation to compare the amount b Assess whether your hypothesis was of heat that is radiated over time from silver, supported or not. white and black aluminium cans. 2 Brainstorm in your group and come up with several different ways to investigate the problem. Select the best procedure and write it in your workbook. Draw a diagram of the equipment you need. 3 Before you start any practical work, assess all risks associated with your procedure. Construct a risk assessment that outlines these risks and any precautions you need to take to minimise them. Show your teacher your procedure and your risk assessment. If they approve, then collect all the required materials and start work. See Activity Book Toolkit to assist with developing a risk assessment. 136 PEARSON SCIENCE 9 2ND EDITION MODULE 4.2 Sound Indigenous Australians developed the didgeridoo thousands of years ago. The player blows air into the didgeridoo while vibrating his lips to produce a low rumbling sound. In addition to the didgeridoo, wind instruments like trumpets, flutes and trombones rely on vibrating air to make sounds. Other instruments, like violins, pianos and guitars, produce sound using strings that vibrate. science 4 fun Straw clarinets Sound waves How does changing the length of a Sound is produced when something vibrates, moving flute or a clarinet change the sound it back and forth very quickly. Table 4.2.1 shows some produces? common sounds and the objects that vibrate to produce Collect this … them. When something vibrates, it passes the vibrations straw into its surroundings, e.g. air. These vibrations create pair of scissors regions of space in which the air particles are bunched Do this … together and regions in which they are more spread 1 Squash the end of the straw and cut it to out. The bunched up areas are called compressions make a point. and the spread-out areas are called rarefactions. Both 2 Blow into the pointy end of the straw. areas are shown in Figure 4.2.1 on page 138. A sound 3 Try different positions until you get a wave is the movement of alternating compressions buzzing sound. and rarefactions. Sound waves travel away from the 4 As you are making the sound, have a source of a sound, in the same way that ripples of water partner carefully cut the other end of your move outwards when a stone is dropped into a pond. straw. TABLE 4.2.1 Common sounds and their sources 5 Keep cutting, making the straw shorter and shorter. Sound Vibrating source Record this … speech folds of skin (called vocal cords) 1 Describe how the sound changed drum drum skin as the straw got piano string inside piano (when you strike a shorter. key, the string is struck by a hammer) 2 Explain how you saxophone reed inside the mouthpiece and think the straw therefore the air inside the saxophone produced a sound. car stereo speaker cone system a bell ringing metal casing of the bell (when struck) CHAPTER 4 HEAT, SOUND AND LIGHT 137  Vibrating speaker air particles A sound wave differs from a transverse wave. In a sound wave, the particles that make up the wave move back and forth in the same direction as the wave is travelling. This type of wave is called a longitudinal wave, or compression wave. This type of wave is shown in Figure 4.2.3. direction of energy flow Push, then pull repeatedly compressions rarefactions compression rarefaction FIGURE 4.2.1 A vibrating speaker produces regions in which air particles are squashed close together (compressions) and regions in which air particles are spaced further apart (rarefactions). The energy moves through air as a sound wave. coil movements wave direction FIGURE 4.2.3 In a longitudinal wave, particles move in the Sound relies upon vibrating particles. This means that same direction that the wave is moving. sound can pass through solids, liquids and gases but not through a vacuum where there are no particles. When a guitar string is plucked, it vibrates and a Hence, sound can pass through railway tracks, water in transverse wave moves along the string. This vibrating a swimming pool and air but not through space. string then sets up a longitudinal sound wave in the surrounding air particles. This is the wave that carries Types of waves the sound to our ear. The differences between these A wave carries energy from one point to another. This waves can be seen in Figure 4.2.4. can happen in two ways. The energy carried by waves Prac 1 p. 145 at a beach moves horizontally, but the particles making up the wave move in a vertical direction. This is shown Transmission of sound in Figure 4.2.2. This vertical movement explains why Sound energy is transmitted through a material as a boat or a seagull floating on the sea bob up and longitudinal waves. The particles of the material vibrate down as a wave travels to the shore. This type of wave as the sound energy flows through it. If you have ever is called a transverse wave. Radiated heat energy is been to a concert or stood near an aircraft that is taking transferred as a type of transverse wave. off, then you will have physically felt the energy that can be transmitted by sound waves. The speed that sound travels through a material depends on the qualities of the material. In general, wave direction if a sound wave hits a dense material, made of lots of particles closely packed together, then the coil movement compressions and rarefactions will travel quickly. As a result, sound travels faster through solids than through FIGURE 4.2.2 In the transverse wave shown here, the particles of the wave vibrate up and down whilst the wave travels liquids, and faster through liquids than through gases. forward. Table 4.2.2 shows that sound travels much faster through glass or steel than through air, the temperature of the material also affects the speed of sound transmission. Guitar string sound wave compression compression compression compression rarefaction rarefaction rarefaction FIGURE 4.2.4 The top or crest of the transverse wave of a vibrating guitar string correlates to the compression of the particles of the longitudinal wave and the bottom or trough of the transverse wave correlates to the rarefaction. 138 PEARSON SCIENCE 9 2ND EDITION The particles of warmer materials vibrate faster than particles in cooler materials. As a result, sound travels SciFile faster through warm air than through cool air and faster through warm water than through cold water. Lightning speed TABLE 4.2.2 Speed of sound in various materials You will see the spectacular effects of Material Speed of sound a fireworks display (metres/second) before you hear the air (at 0°C)   331 explosions. This is air (at 18°C)   342 because light travels much faster than water 1440 sound. wood 4500 steel 5100 glass 5200 A bare and empty room has multiple hard surfaces which reflect sound with little if any absorption Reflection and absorption of (Figure 4.2.6). This causes any sound to bounce around as a series of echoes, allowing the sound to be sound heard for a considerable time. The length of time a You can usually hear people in the next room if they sound can be heard for is known as reverberation. are noisy. This happens because sound passes through Soft materials such as curtain fabric, carpet and thin walls and is transmitted short distances through cushions absorb sound and convert it into heat. This most materials. reduces the reverberation, or length of time a sound is Hard surfaces, such as concrete or bathroom tiles, heard. reflect sound waves. This reflected sound is heard as an echo. The time difference between sending and receiving sound waves can be measured. This difference can be used to calculate the depth of objects under water, using a technique called sonar (sound navigation and ranging), shown in Figure 4.2.5. In this process, a ship sends a sound wave into the water. The sound wave bounces off any hard surfaces in the water such as fish. We can calculate the depth of objects In an unfurnished under water by measuring the time a sound wave takes room, sound reflects from the hard surfaces to bounce off them and return to the ship/surface. and causes echoes. In a furnished room, sound is Acoustic material absorbed by soft furnishings such as this can like heavy curtains, cushions be used to absorb and floor coverings, so there sound in buildings. are few echoes. FIGURE 4.2.5 Sonar can be used to determine the depth of FIGURE 4.2.6 Different materials give a room different objects in the sea, such as this school of fish. reverberation times. CHAPTER 4 HEAT, SOUND AND LIGHT 139  SciFile Boom! Fighter jets regularly travel at supersonic speeds—faster than the speed of sound. As the jet catches up to and then overtakes the sound waves it has produced, a very loud ‘sonic boom’ is heard. Sonic booms can smash windows and damage the hearing of humans, birds and other animals. The sound of this jet breaking the sound barrier has compressed water vapour in the air to form an instantaneous cloud. Sound absorption like this is needed in concert halls, so that there is no overlap between the sounds being performed and their echoes, which would otherwise microphone distort what you hear. Figure 4.2.7 compares how well some materials absorb sound. Typical airborne sound absorption values High 100 90 Low frequency 80 oscilloscope Sound absorption High frequency tuning 70 fork 60 Medium 50 FIGURE 4.2.8 An oscilloscope converts sound waves into 40 electrical signals that can be viewed on a screen. 30 20 Low 10 The wavelength of a sound is the distance between 0 two peaks that are next to each other. It is measured Concrete Brick PVC Nylon Wool acoustic tiles carpet carpet in metres (m). A loud sound has a sound wave with steep peaks, also known as greater amplitude. A soft FIGURE 4.2.7 A comparison of the sound absorption levels of sound has a sound wave with smaller, less steep peaks, different materials also known as lower amplitude. Figure 4.2.9 shows that graphs of louder sounds have larger peaks. Frequency and pitch A dog has a low-pitched growl, whereas a bird chirps sound is with a high-pitched sound. The different sounds can louder but same be compared by analysing their sound waves using frequency an oscilloscope (also known as a CRO), as shown in and pitch Figure 4.2.8. A source that vibrates rapidly produces sound of higher a higher pitch, than one that vibrates more slowly. frequency reference sound and pitch The number of vibrations a sound makes each second but sound is called the frequency of a wave. High frequency is same loudness sound waves have a higher pitch, and low frequency waves have a low pitch. Frequency is measured in FIGURE 4.2.9 A loud sound has a taller graph on an oscilloscope than a quiet sound. Higher-frequency sound waves hertz (Hz). Sound waves also have a wavelength. have a shorter wavelength. 140 PEARSON SCIENCE 9 2ND EDITION  SciFile The Doppler effect high-pitched Have you ever heard the wail of an sound ambulance siren rushing past? When an ambulance travels towards you, the sound waves of the siren bunch up. This makes the sound of its siren higher in pitch. As the ambulance moves away, its sound waves are spread further apart and the sound is lower in pitch. This change in pitch is called the Doppler effect, named after low-pitched sound the Austrian physicist Christian Doppler movement who first described it in 1842. Louder sounds have greater amplitude than softer sounds. The higher the frequency of a wave, the more closely the wave is bunched together and the shorter its wavelength. When we get older, we lose our ability to hear higher frequencies of sound.Young people can typically hear a range of frequencies up to 20 000 Hz, yet most people over 65 years cannot hear frequencies above 5000 Hz. Hence, some mobile phone ringtones cannot be heard by older adults. As we age, more of the tiny hair cells in our inner ear become damaged or destroyed. This happens most easily to the hair cells that we use to hear high frequency sound and once they are destroyed these cells cannot be repaired. FIGURE 4.2.10 Ultrasound waves pass easily through fluids and Many animals, such as dogs and cats, can hear sound soft tissue but are reflected from other layers within the body. frequencies that are outside our human range of Echoes of these waves are detected and analysed by computer to create the image, such as this 3D image of a human foetus. hearing. Ultrasound is the name given to sound waves with frequencies above our hearing range. Bats emit ultrasound squeaks with frequencies up to 200 000 Hz, which reflect off surfaces around them and are used by bats to avoid obstacles and to locate food. Elephants can hear a range of frequencies lower than our own hearing range. These Prac 2 Prac 3 frequencies are called infrasound. p. 145 p. 146 Computer analysis of the way ultrasound reflects from living tissue can be used to create an image, like the one shown in Figure 4.2.10. Musical instruments All musical instruments produce sounds by vibrations (Figure 4.2.11). They do this in different ways and FIGURE 4.2.11 Each of these musical instruments uses produce sounds of differing characteristic qualities. vibration to create its sound. Guitars use vibrating strings, These differences can be compared by playing the trumpets use vibration from the player’s lips and air inside the sound into a microphone attached to an oscilloscope. trumpet, and drums use a vibrating skin. CHAPTER 4 HEAT, SOUND AND LIGHT 141  Typical oscilloscope traces from the sound of four instruments are shown in Figure 4.2.12. On a guitar, a Working with Science violin and a piano, vibrations are produced by strings. Changing the length of the string alters the frequency AUDIO ENGINEER of the sound produced. Longer strings vibrate more Audio or sound engineers are involved in the slowly, producing lower-pitched sound than shorter technical and mechanical aspects of mixing, strings. When you press a string against the neck of a recording, editing and producing sound and music. guitar, you shorten the effective length of that string. They use their skills in a wide variety of industries, including music, film, television and radio. Audio In percussion instruments like drums, the skin engineers work both in and out of the studio. They stretched over the top of the drum vibrates when you are responsible for setting up audio equipment hit it. In instruments like the triangle or the cymbal, the and performing sound checks and live sound instrument itself vibrates. mixing at concerts, sports games and theatre productions (Figure 4.2.13). Audio engineers also In wind instruments, a column of air vibrates. design, develop and manufacture audio software When you play a flute or a recorder, the length of and equipment, such as microphones and sound this vibrating column of air is increased when you boards. More specialised audio engineers are cover holes along the tube, and shortened when you involved in researching the science behind sound leave the holes open. A longer vibrating column of and audio technology. There are many different air produces a lower pitched sound than a shorter areas for audio engineers to specialise in, such as vibrating air column. video game audio design, live sound engineering and recording engineering. To become an audio engineer, you will need to complete an audio engineering and sound production course at TAFE or university. Courses are available from certificate level (for example, Certificate IV in Sound Production) to degree level (for example, Bachelor of Sound and Music Design). Because audio engineering involves a lot of technical skills, an interest in maths, engineering and technology is important. Hands-on experience guitar oboe at a studio, community radio station or production company is a great way to gain valuable skills and learn how the industry works. Audio engineering offers an interesting and diverse career pathway and there are opportunities in a wide range of fields for people with these skills in Australia. piano noise FIGURE 4.2.12 Musical notes produce a smooth, repeating pattern on an oscilloscope. Different instruments produce different characteristic sounds. Background noise shows as an uneven mixture of waves. STEM AB p. 147 4.5 FIGURE 4.2.13 Audio engineers can work in a variety of roles, from recording and mixing music in a studio, to sound checks and mixing at live concerts. Review What kinds of recorded sounds do you hear every day that might have been produced by an audio engineer? 142 PEARSON SCIENCE 9 2ND EDITION  LightbookStarter MODULE 4.2 Review questions LS LS Remembering 9 Predict which of the straws in the science4fun on page 137 would produce: 1 Define the terms: a the highest pitched sound a compression b sound with the longest wavelength b transverse wave c sound of the highest frequency. c frequency. 10 Group the following surfaces into those that 2 What term best describes each of the following? would reflect sound waves and those that would a movement of alternating compressions and absorb sound waves: rarefactions marble tiles in a bathroom b energy carried by the wave moves in the polished floorboards in a school hall same direction as the wave particles carpet on the floor of a cinema c distance a particle in a wave moves from its a glass window rest position. a lounge room with a velvet couch and a deep 3 What is the unit used to measure the following shaggy carpet. quantities? a frequency Applying b wavelength 11 Figure 4.2.14 illustrates three traces of sounds on c speed of sound. an oscilloscope. 4 What is the speed of sound in air at 18 degrees Identify the: Celsius? a sound with the highest frequency 5 What is the source of vibration in a flute? b sound with the lowest frequency 6 Which of the following statements are true and c loudest sound. which are false? a Sound is produced by vibrations. b Regions of high air pressure are called rarefactions. c A sound wave can travel in a vacuum. d Waves at the beach are called transverse A B C waves. FIGURE 4.2.14 Understanding 7 Explain why sound travels faster through solids Analysing than through liquids. 12 Analyse the oscilloscope patterns of the sound from a guitar, oboe and piano in Figure 4.2.12 8 a What is meant by the term reverberation? on page 142. b Explain why an empty room is full of echoes. a Which instrument was being played the c Predict what happens to those echoes as loudest? furniture, curtains and carpet are moved into b Which instrument had the lowest pitch? the room. c Compare the patterns of musical instruments with the shape of the trace that is shown for noise. CHAPTER 4 HEAT, SOUND AND LIGHT 143  MODULE 4.2 Review questions 13 For the ocean wave shown in Figure 4.2.15, 15 Analyse Figure 4.2.7 on page 140 to complete determine the: the following. a wavelength of the wave a Which material listed best absorbs high b amplitude of the wave. frequency sounds? b Which material reflects the highest i  1.2 m proportion of sounds? ii Propose a reason why this material does not absorb much sound. 0.4 m 0.6 m 0.6 m c Explain what happens to the sound energy absorbed by materials. 16 Voice recognition uses computer programs to identify speech. How do you think these programs work? FIGURE 4.2.15 Creating 14 Refer to the illustration of the air particles in a 17 Construct a diagram to contrast ultrasound with sound wave shown in Figure 4.2.16 to complete infrasound. the following questions. a Determine the wavelength of this sound wave. b What would be the distance shown as x in the diagram? c Do the points marked A and B show a compression or a rarefaction? d Describe the difference in air pressure that would exist at points A and B. 25 cm A B x FIGURE 4.2.16 144 PEARSON SCIENCE 9 2ND EDITION  MODULE 4.2 Practical investigations 1 Spring waves 6 Tap one end of the spring horizontally so that a pulse travels through the spring, as shown in Purpose Figure 4.2.17b. To model transverse and longitudinal waves. 7 Try to draw what is happening here from a side Timing 30 minutes view. This is a longitudinal wave, like a sound Materials wave. slinky spring 8 Try to alter how you produce these waves to Procedure increase their frequency. 1 Hold one end of the slinky. A partner holds the Review other end. Take care not to overstretch the slinky. 1 Describe how the slinky moves when a: 2 Move your end of the slinky up and down at a a transverse wave passes through regular speed, as shown in Figure 4.2.17a. b longitudinal wave is transmitted. 3 Sketch a side view of the waves you made. These a 2 How were you able to increase the frequency of are transverse waves, like water waves. the following waves? 4 Try to alter how you produce the waves so that a transverse waves they are bunched closer together, with greater b longitudinal waves. frequency. 3 Which of the two waves you produced is more 5 You and your partner hold each end still. like a sound wave? a b FIGURE 4.2.17 b 2 Good vibrations PART B 3 Line up the beakers (or glasses) on your bench. Purpose 4 Fill each beaker to a different depth with water. To investigate the differences in producing high- 5 Carefully tap the glass of each using the pen, pitched and low-pitched sounds. chopstick or other object, and listen to the Timing 45 minutes variation in pitch. Materials Review water 1 Did the longer or shorter length of vibrating ruler make the highest pitched sound? 5 beakers (or glasses) of the same size 2 Construct a graph that shows the difference pen or a chopstick between sound waves produced. ruler 3 Describe the pitch of sound produced by the Procedure beaker with the least amount of water. PART A 4 How do you think that the length of the ruler and the depth of water in the beaker are related to the 1 Hold the ruler over the edge of a bench and flick pitch of sound they produce? it so it vibrates. 5 Do you think the vibrations would be faster or 2 Listen to how the pitch changes as you reduce slower when producing higher pitched sounds? the length of ruler vibrating. 6 Try and recreate a well-known tune, such as ‘Happy birthday’. CHAPTER 4 HEAT, SOUND AND LIGHT 145  MODULE 4.2 Practical investigations 3 Producing sound Purpose To see and hear the vibrations that produce a sound vibrating tuning fork wave. Timing 30 minutes Materials water glass selection of tuning forks rubber mallet or rubber stopper water 100 mL beaker wooden bench top or sounding box Procedure FIGURE 4.2.19 1 Strike a tuning fork with a rubber mallet or on a soft surface such as a rubber stopper or a book. 8 Extension: 2 Place the ends of the tuning fork carefully Place two identical tuning forks in two sounding towards your ear and see if you can hear a sound. boxes (Figure 4.2.20). Strike the first tuning fork and carefully observe to see if the second 3 Strike the tuning fork again and this time hold it tuning fork vibrates without being struck. This on a bench top (Figure 4.2.18) or position it in a phenomenon is called resonance. hollow wooden sounding box. rubber mallet strikes tuning fork FIGURE 4.2.20 FIGURE 4.2.18 Review 1 a Describe the difference you observed in the 4 Repeat the previous step using a selection of sound produced before and after the tuning tuning forks that are designed to produce sound fork was placed on a bench top or sounding of differing frequencies. box. 5 Half fill a beaker with water. b Propose why the sound changes in this case. 6 Strike the tuning fork and insert its ends into the 2 a Describe the effect of placing the tuning fork water as shown in Figure 4.2.19. Observe the into the water. water. b How can this provide evidence that the ends of the tuning fork are vibrating? 7 Repeat the previous step but record what happens using a phone or video camera. 3 Compare the pitch of the tuning fork with the frequency in hertz (Hz) that is inscribed at its base. Which tuning fork would produce a higher pitched sound: 256 Hz or 512 Hz? 146 PEARSON SCIENCE 9 2ND EDITION  4.2 Practical investigations ISTEM MODULE N Q U I RY Energy efficient house Background Engineering design process You are employed by a construction firm. This firm The engineering design process is outlined in is known for developing house designs that are Figure 4.2.22. sustainable, energy efficient and have spaces suited Identify the purpose. to specific needs, such as a wine cellar/cool room Identify the independent, dependent and and a cinema room/music studio. controlled variables and only change one variable A client is looking for a house design that uses the at a time. best materials and concepts. The client is a musician Based on your purpose and the controls and and environmentalist. Her house will be located variables, write a hypothesis for this experiment. in an area where summer and winter weather Before you commence your investigation you conditions are extreme. must conduct a risk assessment and write down Problem safety measures that you will follow to keep Your job is to provide information to the construction yourself and other students safe. firm about energy efficient designs, materials and See Activity Book Toolkit to assist with specific plans for specialty rooms. Using research developing a risk assessment. then trialling materials for heat-proofing or sound- Summarise your experiment in a scientific report proofing, you will present the firm with the best including the Purpose, Hypothesis, Materials, des