THERMAL ENERGY

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I. Energy (Science textbook page E94-E95)

Energy is not a type of matter because it does not have a mass and it does not occupy space.

Energy is the ability to do work or to move matter around. Work is using a force to move an object. There are different types of energy.

Kinetic energy is the energy of movement. Ex: A boy who is running.

Potential energy is stored energy. Ex: A ball at the top of stairs, an arrow ready to be thrown on a bow and arrow.

Matter always has at least one of these forms of energy (kinetic or potential).

II. Thermal energy (= energy of heat) Heat: The transfer of thermal energy from one object to another. Heat always flows from HOTTER materials to COOLER materials. Temperature: The measure of thermal energy. When an object gains energy its temperature rises, when an object loses

energy, its temperature decreases. High temperatures mean that the molecules are moving faster and have lots of energy. Lower temperatures mean the molecules are moving more slowly and have less energy.

III. How does heat move? (Science textbook E97) Heat can flow in 3 ways.

CONDUCTION CONVECTION RADIATIONDirect Contact

Occurs mainly in solidsEX: Hands on a mug of hot chocolate.

Hot parts of a material rise, while cooler part sink.In liquids and gases.Ex: Pot of water on a stove.

Transfer of heat through electromagnetic rays.No matteris needed.Ex: Rays of the sun that warms the Earth.

IV. Conductors (Science textbook E98) Best conductors of heat: Metals (aluminum, copper, iron,…). Poor conductors of heat, good insulators: wood, glass, air, plastic, foam.

Heat Transfer

1. Which of the following substances is a good conductor of heat?

A. wood

B. glass

C. plastic

D. metal

2. Imagine that you are baking brownies for a bake sale at school.

Which of the following pans is least likely to cause you to burn the bottoms of your brownies?

A. a copper pan

B. an aluminum pan

C. a glass pan

D. a cast iron pan

3. Brittany placed a cold piece of butter on a hot ear of corn. The butter began to melt.

The butter melted when it came into contact with the corn because heat was transferred from the corn to the butter by _______.

A. conduction

B. evaporation

C. radiation

D. convection

4. Sometimes manufacturers do not want heat to be conducted through certain parts, such as the handles of pots, the steering wheels in cars, and swings on playgrounds.

What material are these parts likely to be made out of?

A. copper

B. aluminum

C. steel

D. plastic

5. The picture shows how adding heat or taking heat away causes matter to change state.

What is it called when a solid is formed by removing heat from a liquid?

A. condensation

B. evaporation

C. freezing

D. melting

6. Radiation occurs when heat is transferred

A. through space.

B. by the direct contact of two objects.

C. through solid particles.

D. through liquid particles.

7. Mr. Polifka does a demonstration in science class. He holds an unlit match six inches above a candle flame. After a while, the match bursts into flame.

What most likely caused the match to catch fire?

A. Matches are flammable—they catch fire when exposed to air.

B. Heat from the candle flame was transferred to the match.

C. The match absorbed heat from the air until it was hotter than its environment.

D. A spark from the flame leapt up to the match and caught it on fire.

8. On a summer afternoon, the sand on the beach can get very hot. When you step on the sand in bare feet, you can burn yourself.

Which of the following sentences best describes how this happens?

A. Heat from the Sun is transferred to the sand by direct contact. This heat is then transferred to your feet by direct contact.

B. Heat from the Sun is transferred to the sand by direct contact. This heat is then transferred to your feet without direct contact.

C. Heat from the Sun is transferred to the sand without direct contact. This heat is then transferred to your feet by direct contact.

D. Heat from the Sun is transferred to the sand without direct contact. This heat is then transferred to your feet without direct contact.

9.

The picture above shows a frying pan. Why are frying pans usually made out of metal?

A. because metal is a poor conductor of heat

B. because metal is a good conductor of heat

C. because metal is a poor conductor of electricity

D. because metal is a good conductor of electricity

10. Johnny has been sitting on the rock at point X near the campfire, shown below. The fire produces heat energy.

What will happen if he moves to point Y?

A. He will be more likely to get burned.

B. The temperature will not change.

C. He will feel colder.

D. He will feel warmer.

11. Which of the following is an example of heat being transferred by conduction?

A. a cup warming in the microwave

B. a pot on a hot stove

C. a car sitting in the sun

D. a pan baking in the oven

12. The picture shows how adding heat or taking heat away causes matter to change state.

A gas forms when enough heat is added to _______  a liquid.

A. melt

B. condense

C. freeze

D. boil

13. If a metal spoon is placed in a cup of hot water, the spoon will

A. stay the same temperature.

B. get hot.

C. melt.

D. get cold.

14. Which of the following is an example of heat being transferred from one object to another without direct contact?

A. Caleb burned himself by holding his hand too close to a fire for too long.

B. Caleb burned himself by taking a shower in water that was too hot.

C. Caleb burned himself by touching the end of a poker that was sitting in a fire.

D. Caleb burned himself by spilling a hot drink on his hand.

15. Vivian poured some water into a bottle. She placed the bottle into the freezer until the water became ice. What property change did the water go through?

A. The water changed from big to small.

B. The water changed from hard to soft.

C. The water changed from clear to white.

D. The water changed from a liquid to a solid.

16. Warm air and water both tend to rise while cooler air and water sink. When different parts of the oceans are heated unevenly, this causes the water to

A. move in convection currents.

B. form a tsunami.

C. stay in the same place.

D. mix together in the water cycle.

17. What happens when a body of cold air approaches a body of warm air?

A. The cold air rises.

B. The warm and cold air both disappear.

C. The warm air rises.

D. The warm and cold air mix immediately.

18. The Earth receives electromagnetic energy from the Sun.

How does the electromagnetic energy from the Sun travel through empty space to reach the Earth?

A. by convection

B. by conduction

C. by radiation

D. by evaporation

19. When does heat naturally move from warmer objects to cooler objects?

A. when the objects are touching

B. always

C. never

D. when one of the objects is a good conductor of heat

20. Through which of the following ways can heat be transferred?

A. Heat can never be transferred between objects.

B. only by direct contact between objects at different temperatures

C. only by indirect contact between objects at different temperatures

D. by direct or indirect contact between objects at different temperatures

21. Jasmine has toast for breakfast every day. As soon as the toast pops out of the toaster, she puts butter on it. If she does it quickly, she can spread the butter over the toast with her knife, and it melts into the toast.

Why does the butter melt?

A. because heat from Jasmine's hand moves into the cool butter

B. because heat from the hot toast moves into the cool butter

C. because the pressure of her knife softens the butter

D. because heat from the hot knife moves into the cool butter

22. Josiah is going to have a cup of hot cocoa. If he wants the cocoa to stay warm as long as possible, which type of cup should he put his hot cocoa in?

A. a glass cup

B. a foam cup

C. an iron cup

D. an aluminum cup

23. Some cooking spatulas are made out of plastic.

Why are cooking spatulas often made out of plastic?

A. Because plastic is a poor conductor of heat, and this keeps the handle from getting too hot to touch while cooking.

B. Because plastic is a good conductor of electricity, and this makes it safe to use while cooking.

C. Because plastic is a good conductor of heat, and this keeps the handle from getting too hot to touch while cooking.

D. Because plastic catches fire very easily when it is used for cooking.

24. Alonzo has a hot brick. He knows that a hot object can transfer its heat to other objects in three ways:

by touching other objects

by touching air, which carries the heat to other objects

by radiating the heat away like light radiates from a light bulb.

Alonzo designs an experiment to test how quickly the brick will transfer its heat to the rest of the room. The table below shows in which of the three ways the brick can lose heat for each way Alonzo plans to set up the brick.

Way of transferring heat

Situation Touching Objects

Touching Air

Radiating like a light bulb

 1  The brick sits on a piece of metal with a fan blowing air over it

 2  The brick sits in a metal box with air flowing through it.  

 3  The brick is hung in the middle of a room  

 4  The brick is hung in a room with no air in it    

Alonzo now needs to make a prediction about what will happen. In which situation will the brick stay the warmest longest?

A. 4

B. 3

C. 1

D. 2

25. Margie and her class are doing an experiment. They first fill a large jar with hot water and a small jar with cold water. Then, they add red food coloring to the small jar of cold water and cover the jar with foil. A hole is poked in the foil, and the small jar is turned over and placed on top of the large jar. The cold, red-colored water slowly flows through the hole from the small jar to the large jar.

Which of the following will likely occur as the cold red-colored water mixes with the hot water?

A. The red-colored water will stay at the top of the large jar.

B. The red-colored water will spread through the large jar quickly, then sink to the bottom.

C. The red-colored water will sink at first, then slowly spread through the large jar.

D. The red-colored water will instantly spread through the large jar.

26. At 0°C, frozen water (ice) changes to liquid water. When an ice cube is placed on something that is warmer than it, heat will move from the warmer substance to the water until

A. the ice reaches 0°C.

B. the ice melts.

C. both objects are the same temperature.

D. the warmer substance cools to 0°C.

27. Cynthia gets two glasses of cold water. She sets both glasses down. She sets one in the sunlight. The second she sets in the shade.

As the glasses of water sit, what will happen to the temperature of the water?

A. The water will get warmer. The glass in the sun will be warmer than the glass in the shade.

B. The water in each glass will get warmer until it boils.

C. The water in the glass in the shade will get cooler. The water in the glass in the sun will get warmer.

D. The water in both glasses will stay cold.

28. Which of the following is the best example of heat being transferred from one object to another by direct contact?

A. A drink can be cooled off by dropping ice cubes into it.

B. The coldest air in the supermarket is in the aisle where the frozen foods are kept.

C. A fire in a fireplace warms the entire room.

D. Sunlight feels warmest when it falls directly on a person's skin.

29. Which of the following is an example of heat being transferred by radiation?

A. an electric heater warming a room

B. a fire warming a group of campers

C. the Sun heating the Earth

D. all of these

30. Nate has four hot plates. Each hot plate is set at a different temperature.

Nate also has four identical pieces of ice. He puts one piece of ice on each hot plate. Which of the following is true?

A. The ice will melt at the same rate on all of the hot plates.

B. The ice will melt the fastest on hot plate 2.

C. The ice will not melt on any of the hot plates.

D. The ice will melt the slowest on hot plate 3.

31. Pauline is going on a picnic, and is bringing some sandwiches. She wants to keep the sandwiches cold for as long as possible by putting them in a cooler.

Which of these would be the best material for Pauline's cooler to be made of?

A. iron

B. plastic

C. glass

D. aluminum

32. Tony wants to figure out which materials conduct heat better than others. To do this, he fills cups that are made out of different materials with equal amounts of ice water. He then keeps track of how much time it takes the ice to completely melt in each cup. His results are below.

Time for Ice to Melt

Cup Material Time to Melt

plastic 32 minutes

glass 21 minutes

aluminum 15 minutes

foam 38 minutes

Which material was the best conductor of heat?

A. foam

B. glass

C. plastic

D. aluminum

33. In order for heat to be transferred by conduction, which of the following must occur?

A. A hot object must be directly touching a cold object.

B. The Sun must heat the cold object.

C. A hot object must be placed near a cold object.

D. A cold object must be heated with hot air.

34. Dianne's teacher has a chunk of dry ice for the class to look at. Dry ice is a kind of frozen gas—it is very cold. The teacher warns her class not to touch it. When Dianne holds her hand near it, it feels like the dry ice is radiating cold.

What is really happening?

A. Heat energy from Dianne's hand is being transferred to the dry ice even though she is not touching it.

B. Small pieces of the dry ice are breaking off and hitting Diane's hand, making it feel cold.

C. Cold energy from the dry ice is being transferred to Diane's hand even though she is not touching it.

D. Chemicals in the dry ice are tricking Diane's nerves into thinking she feels cold.

35. Cody notices that if he stirs his hot oatmeal quickly, two things happen:

Much more steam rises from his oatmeal than when he does not stir it.

His oatmeal cools off much more quickly than when he does not stir it.

What happens to the heat energy of Cody's oatmeal when he stirs it that makes it lose heat more quickly?

A. The spoon is a conductor of heat that moves most of the heat of the oatmeal away from the oatmeal.

B. The stirring motion creates friction in the oatmeal that adds heat energy to the oatmeal.

C. The heat energy of his oatmeal changes into the energy of motion of his moving oatmeal.

D. Stirring it releases steam, which transfers heat from his oatmeal to the air.

36. Bianca is sitting in front of the fireplace.

Bianca feels heat coming from the fireplace, even though she is not touching it. This is because the heat from the fireplace is being transferred by _______.

A. conduction

B. radiation

C. evaporation

D. convection

37. At room temperature, good conductors of heat usually feel cool to the touch. This is because they conduct heat so quickly, that when a finger touches them, the heat from the person's finger is immediately conducted away.

From this information, which of these materials is probably the best conductor of heat?

A. cotton

B. glass

C. plastic

D. wood

38. What causes liquid water to freeze?

A. when heat from the water is transferred to something else

B. when cold from something else is transferred to the water

C. when cold from the water is transferred to something else

D. when heat from something else is transferred to the water

39. If a substance conducts heat easily, it is considered to be a

A. good conductor.

B. bad substance.

C. poor conductor.

D. good insulator.

Answers1. D 2. C 3.A 4.D 5.C 6.A 7.B 8.C 9.B 10.C 11.B 12.D 13.B 14.A 15.D 16.A

17.C 18.C 19.B 20.D 21.B 22.B 23.A 24.A 25.C 26.C 27.A 28.A 29.D 30.B 31.B 32.D 33.A 34.A 35.D 36.B 37.B 38.A 39. A