Science 7 Unit C: Heat and Temperature. Topic 6. Transferring Energy. pp WORKBOOK. Name:

Transcription

1 Science 7 Unit C: Heat and Temperature Topic 6 Transferring Energy pp WORKBOOK Name: 0

2 Read pp object or material that can transfer energy to other objects Example: light bulb, the Sun Methods of Energy Transfer 1) Radiation 2) Conduction 3) Convection Radiation transfer of energy without any movement of matter energy transferred this way is called or (EMR). o travels through empty space, air, glass and many other materials o there are many forms of EMR: radio waves, microwaves, visible light (ROYGBIV), X-rays if the energy source is a warm object, like the Sun, then some of its thermal energy is transferred as infrared radiation (IR) all radiant energy shares several characteristics: o behave like waves o can be absorbed and reflected by objects o can travel across empty space at the same very high speed ( km/s) Discuss Find Out Activity p. 227 (thought experiment) dark, dull objects absorb more radiant energy than light, shiny objects that reflect Read Off the Wall p

3 TASK: Complete the Decision Making Investigation 3-G on p. 228 Comparing Surfaces Please record your answers below or on an attached sheet of loose leaf. Think About It From your own experience, can you think of examples of the following scientific observations? Dark coloured surfaces absorb and radiate energy better than light coloured ones. Dull surfaces absorb and radiate energy better than shiny ones. Light coloured surfaces reflect radiate energy better than dark colours ones. Procedure 1. Complete the following table to describe the behaviour of each surface. ( = better, X = worse) Title: Ability to Surface Absorb Radiate Reflect light coloured X X dark coloured shiny texture dull texture 2. Identify the combination so color and texture that would be the a. Best reflector c. Best absorber b. Worst reflector d. Worst radiator Analyze 2

4 Radiation BLM 3-20 Goal: Check your knowledge and understanding of radiation. What to Do Answer the following questions in the space provided. 1. When you sit in front of a fire, you feel warmed by radiant energy. When someone stands between you and the fire, you feel cold again. Explain why this happens. Draw and label a diagram to illustrate your explanation. 2. Why are white or light-coloured clothes recommended for hot, sunny locations? 3. Why did the Apollo astronauts wear shiny suits on the moon? 4. Explain how insulation between the outer and inner walls of a home helps to reduce thermal energy transfer. 5. Explain how a reflective film on windows helps to keep a home cool in the summer but warm in the winter. 3

5 Read p. 229 Conduction transfer of thermal energy by contact direct collisions between particles reduce transfer of thermal energy to or from its surroundings Conduction BLM 3-21 Goal: Check your knowledge and understanding of thermal conduction. What to Do Answer the following questions in the space provided. 1. On a cold winter day, why would an iron post in a park feel much colder to the touch than a wooden bench? 2. Potatoes cook from the outside in. (a) Why does a small potato cook faster than a large potato? (b) Why does sticking a metal skewer through the middle of a potato make it cook faster? 3. A metal spoon is used to stir a pot of hot soup. Draw three diagrams to show the behaviour of the particles in the spoon. Write captions to help explain what each diagram illustrates 4

6 Radiation Conduction Thermal energy is transferred from the heat source in the form of a wave. Particles near the heat source absorb energy from it. They begin to vibrate more rapidly. The wave can travel through materials, and even through empty space. The fast-moving particles bump into neighbouring particles, increasing their energy and motion. The radiant energy is absorbed or reflected by objects in the path of the wave. Neighbouring particles bump into their neighbours, and so on. In this way, thermal energy is transferred throughout the material. 5

7 Read p. 230 Convection thermal energy can also be transferred by o materials that can be poured or that flow from place to place i.e. liquids and gases warm fluid moves around and carries thermal energy warmer fluid expands, becomes less dense, and rises rising fluid, moving away from the heat source, cools, and contracts denser cooled fluid sinks, pushing nearby warmer fluid upwards colder fluid that replaced warm fluid is warmed again by the heat source process repeats, creating continuous fluid movement in the form of currents See Figure 3.25 p. 230 Read Career Connect p

8 Convection BLM 3-22 Goal: Apply your knowledge and understanding of convection currents in nature. What to Do Answer the following questions in the space provided. 1. During the winter, colder water near the surface of a pond sinks. Warmer water at the bottom of the pond rises. a) Why are convection currents important for pond life? b) Can you suggest a reason why ponds become stagnant in the summer? c) What could happen to the biotic components of a pond if convection did not occur? 2. How can birds use warm air currents? 7

9 Convection BLM 3-22 Continued 3. Sea and land breezes are convection currents that occur in nature. Warmer air rises and cooler air moves in to take its place. a) During the day, the land heats up faster than the sea. The warmer air above the rises. This allows the sea air to move in, causing a sea breeze. In the space below, draw and label a diagram of the air currents during a hot, sunny day by the sea. b) During the night, the land cools faster than the sea. The warmer air above the rises. The cooler air over the moves in to take its place, creating a land breeze. In the space below, draw and label a diagram of the air currents during a night by the sea. c) Under what conditions would no breezes occur? d) Explain how cold temperatures along a beach affect the direction of a sea breeze. 8

10 Convection Particles near the heat source absorb energy and become warmed. The less dense, warmed column of particles pushes up through the fluid. The surrounding cooler particles sink and move in to replace the rising column of warm particles. 9

11 Read pp Energy Transfer Systems Common Features: 1) Energy Source some part of the system acts as an energy source supplying energy to the rest of the system; the source can be mechanical, chemical, nuclear or electrical 2) Direction of Energy Transfer energy is always transferred away from concentrated sources 3) Transformations energy doesn t necessarily keep the same form as it is transferred from place to place 4) Waste heat almost all energy systems transfer at least a little thermal energy into the surroundings 5) Control systems some way of adjusting energy transfers Heat Energy Systems BLM 3-24 Goal: Recognize that heat energy systems are a specific type of energy system. Think About It All energy systems require input energy from a source. All energy systems change the form of input energy into a desired output energy form. What to Do Complete the chart to see how we change one form of energy into heat energy, and then use this heat energy to our advantage. Answer the following questions in the space provided. Device Source (Input Energy) Direction of Energy Transfer Transformation Control System Hair Dryer Light Bulb Car Engine Bicycle Brakes Where does all the waste heat go in each of these systems? 10

12 Discuss Find Out Activity p. 235 Insulation and RSI Values BLM 3-30 Goal: Practice solving problems related to insulating materials and their RSI values. What to Do Answer the following questions in the space provided. Show all your work. 1. Complete the following table. Insulating Material RSI value/cm Thickness (cm) Total RSI value fibreglass vermiculite plywood glass clay brick Explain which is a better insulator, plywood or glass, if the same thickness of material is used? 3. The total RSI value of a wall is found by adding together the RSI values for the different layers of insulating material. In the space below, calculate the total RSI value of a wall that has 10 cm of clay brick, 15 cm of fiberglass, and 1 cm of plywood. 4. In the space below, calculate the thickness of vermiculite that will provide the same resistance to conduction as 4 cm of fiberglass. 11

13 Energy Transfer Systems BLM 3-27 Vocabulary Check What to Do Complete the following crossword puzzle using the clues provided. Across 2. systems that regulate the energy transfer process 3. property of energy transfer that is always away from the source 6. something that can happen to energy as it is transferred from place to place 9. thermal energy that is unintentionally released into the surroundings 10. type of energy that is provided by gasoline, diesel fuel, or food Down 1. information that is returned to a system to help maintain its efficient operation 3. property that eventually becomes the same throughout a system when thermal energy is transferred from hot objects to cooler objects 5. concentration of energy before it is transferred 7. energy from substances whose smallest particles are fused or broken apart, releasing large amounts of energy 8. term that means the total energy of a system stays the same 12

14 Read Did You Know p. 236 Complete Topic 6 Review Questions p. 236 #1-4 Please record your answers below or on an attached sheet of loose leaf. 13