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Science 7 Unit C: Heat and Temperature

Topic 6

Transferring Energy pp. 226-236

WORKBOOK

Name: _____________________________

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Read pp. 226-227

_____________________ 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 (300 000 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. 228

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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

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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.

4

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

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Radiation

Thermal energy is transferred from the

heat source in the form of a wave.

The wave can travel through materials,

and even through empty space.

The radiant energy is absorbed or

reflected by objects in the path of the

wave.

Conduction

Particles near the heat source absorb

energy from it. They begin to vibrate

more rapidly.

The fast-moving particles bump into

neighbouring particles, increasing their

energy and motion.

Neighbouring particles bump into their

neighbours, and so on. In this way,

thermal energy is transferred throughout

the material.

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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. 230

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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?

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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.

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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.

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Read pp. 231-233

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?

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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 0.24 5

vermiculite 2 0.32

plywood 0.087 0.35

glass 0.017 7

clay brick 10 0.07

2. 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.

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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

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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.