Energy Basics & Electromagnetic Energy

Heat energy transfer will normally occur between two objects that are close to each other if the objects have different

• specific heats

• temperatures

• masses

• densities

Answer explanation

o Heat energy moves from a warmer object to a cooler object. If two objects have different temperatures, energy will flow from the hotter object to the colder one until they reach the same temperature.

When a heat source loses energy, that energy is

• reflected by a heat sink

• refracted by a heat sink

• scattered by a heat sink

• absorbed by a heat sink

Answer explanation

o A heat sink is something that absorbs heat energy. For example, if you place a hot metal spoon in cold water, the spoon loses heat, and the water absorbs it.

The pictures below show pairs of metal blocks and their temperatures. Which of these correctly shows the direction that heat energy will move?

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Answer explanation

o Heat always moves from a higher-temperature object to a lower-temperature object. The correct diagram should show heat flowing from the warmer block to the cooler block.

Which of the following figures correctly shows the directions of heat flow within the system of the metal blocks?

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Answer explanation

o Heat spreads through conduction in solids, moving from hotter areas to cooler areas. The correct answer will show heat moving from the hottest block toward the cooler ones.

Three metal cubes are heated to the temperatures shown and placed in contact with one another on a non-conducting surface. The picture below shows the cubes next to one another and their temperatures.
In which direction does heat energy begin to flow between the metal cubes?

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Answer explanation

o The cube with the highest temperature will transfer heat to the cubes with lower temperatures.

A teacher put one test tube of 50°C liquid and one test tube of 10°C liquid into a 20°C water bath, as shown in the diagram below.
Which of the following diagrams best represents the directions that heat will move when the test tubes are placed into the water bath?

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Answer explanation

o Heat will flow from the warmer test tube (50°C) to the warmer water (20°C), and at the same time from the warmer water (20°C) to the cooler test tube (10°C).

A solid object at 30°C is placed inside a container of liquid at 60°C. What will most likely be observed?

• The temperature of the liquid will remain the same.

• The temperature of the solid object will decrease.

• The temperature of the liquid will increase.

• The temperature of the solid object will increase.

Answer explanation

o Heat moves from the warmer liquid (60°C) to the cooler solid (30°C).

The diagram below shows a melting ice cube. Which statement best describes the energy transfer?

• The meltwater is a heat source and the surrounding air is a heat sink.

• The meltwater and ice cube are both heat sources.

• The ice cube and surrounding air are both heat sources.

• The ice cube is a heat sink and the surrounding air is a heat source.

Answer explanation

o The ice cube absorbs heat from the warmer air, causing it to melt. The warmer air is the heat source.

9. Kaleigh placed a glass of ice cubes on the table. The temperature inside the glass was 0˚C. Thirty minutes later, the glass contained water and smaller ice cubes at a temperature of 4˚C. Which best describes the transfer of energy that occurred as the ice melted?

• The water transferred heat to the air.

• Ice transferred heat to the glass.

• Air transferred heat to the ice.

• The glass transferred heat to the table.

Answer explanation

o The air around the glass is warmer than the ice, so heat moves from the air into the ice, causing it to melt.

The diagram below shows temperature values at various points in a solid piece of aluminum. Toward which point will heat flow from point P?

• A

• B

• C

• D

Answer explanation

o Heat always moves from hotter regions to cooler ones, so it will travel toward the area with the lowest temperature.