Chapter 4.1 Review - Heat

Front 1

State the temperature on the Fahrenheit, Celsius and Kelvin scales at which water freezes.

Back 1

Water freezes at: 32 degrees on the Fahrenheit scale, 0 degrees on the Celsius scale and 273 Kelvin.

Front 2

Heat always flows from an object of higher temperature to one of lower/higher temperature.

Back 2

Heat always flows from an object of higher temperature to one of lower temperature.

Front 3

Insulators are good/poor conductors of heat.

Back 3

Insulators are poor conductors of heat.

Front 4

Gases are good/poor conductors of heat.

Back 4

Gases are poor conductors of heat.

Front 5

On a warm day, a house is warmer upstairs because of conduction/convection currents.

Back 5

On a warm day, a house is warmer upstairs because of convection currents.

Front 6

The element of a hot water system will be located near its top/base and the heat is spread by convection.

Back 6

The element of a hot water system will be located near its base and the heat is spread by convection.

Front 7

List three insulators.

Back 7

Three insulators— plastic, air, cloth, rubber, wool, polystyrene (or other alternatives).

Front 8

Describe how heat is conducted along a metal rod.

Back 8

Particles in the metal rod near the source of the heat vibrate faster. These vibrations are passed on to nearby particles, which also vibrate with increased kinetic energy. The transfer of heat occurs as particles in contact transfer this kinetic energy along the metal rod.

Front 9

Figure 4.1.2 on page 100 shows saucepans X and Y of water being supplied with equal amounts of heat energy. Explain why the temperature rise in saucepan X is greater.

Back 9

The water in saucepans X and Y absorbs equal amounts of heat energy. As there are fewer water particles in saucepan X, each particle absorbs more energy. This means these particles will vibrate faster and their average kinetic energy, or temperature is greater than that of saucepan Y.

Front 10

A wetsuit traps a layer of water between the wearer and the fabric of the suit. State whether water is a good or poor conductor of heat.

Back 10

Water is a poor conductor of heat.

Front 11

A wetsuit traps a layer of water between the wearer and the fabric of the suit. Explain how this design helps to keep the wearer of the suit warm.

Back 11

Being a poor conductor, this layer of water does not effectively transfer the body heat from the wearer of the suit to the fabric of the wetsuit. This allows the wearer to stay warmer.

Front 12

Explain why the vents for a ducted heating system are usually placed near the floor and not the ceiling.

Back 12

Warmer air released from the heating vents will rise, to a point where it cools and then falls as more hot air rises to take its place. This process of convection heats up a room. If the vents were placed near the roof, the room would still be warmed but the process would not be as effective.

Front 13

You lose a lot of heat from your head. For most people, their hair protects them from losing too much heat from their heads. Explain why hair is an effective insulator.

Back 13

Hair traps pockets of air close to your head. Air is a poor conductor of heat, and this minimises the heat you lose from your head. In this way, hair is an effective insulator.

Front 14

You lose a lot of heat from your head. For most people, their hair protects them from losing too much heat from their heads. Describe a hair style that would give you excellent insulation.

Back 14

hairdo that has a thick layer of hair insulating the head would trap the heat. An example is long hair wrapped into a bun at the top of the head.

Front 15

Heat transfer can occur by conduction, convection or radiation. Identify the main method of heat transfer in each situation below. Your feet get hot when you are walking on sand at the beach.

Back 15

conduction.

Front 16

Heat transfer can occur by conduction, convection or radiation. Identify the main method of heat transfer in each situation below. Your back feels warm when you are sitting in the sun.

Back 16

radiation.

Front 17

Heat transfer can occur by conduction, convection or radiation. Identify the main method of heat transfer in each situation below. You boil water in an electric kettle.

Back 17

convection.

Front 18

Heat transfer can occur by conduction, convection or radiation. Identify the main method of heat transfer in each situation below. You feel cold when you dive into a swimming pool.

Back 18

conduction.

Front 19

Heat transfer can occur by conduction, convection or radiation. Identify the main method of heat transfer in each situation below. You feel warm air as you walk into a school disco held in a hall.

Back 19

radiation.

Front 20

Compare heat and temperature.

Back 20

Heat is the total energy contained within a substance, whereas temperature is the average kinetic energy of its particles.

Front 21

Compare the Fahrenheit, Celsius and Kelvin temperature scales.

Back 21

Similarities—the Fahrenheit, Celsius and Kelvin temperature scales: have increments of the same size, are based on at least one fixed point, increase as substances get warmer.
Differences: Fahrenheit and Celsius are measured in degrees, whereas Kelvin temperatures are not, Water freezes at 0 degrees Celsius, 32 degrees Fahrenheit and 273 Kelvin.

Front 22

Two identical bathtubs are filled to the same level with water. The particles in bathtub A move with greater speed than the particles in bathtub B. State in which bathtub the water will be at a higher temperature.

Back 22

The water in bathtub A is at a higher temperature.

Front 23

Two identical bathtubs are filled to the same level with water. The particles in bathtub A move with greater speed than the particles in bathtub B. State which bathtub has more heat energy.

Back 23

The water in bathtub A has greater heat energy.

Front 24

Two identical bathtubs are filled to the same level with water. The particles in bathtub A move with greater speed than the particles in bathtub B. As the water cools, each bath loses heat energy. List three places this heat energy could go.

Back 24

Heat will be transferred to the bath itself, any objects floating in the bath and to the air surrounding the bath.

Front 25

Figure 4.1.17 shows the experimental set-up for a radiation experiment. The same sized black and white cardboard squares are attached to two thermometers close to an incandescent globe. Propose what the student performing the experiment is trying to test.

Back 25

The student is comparing the amount of infrared radiation absorbed by a black cardboard square and a white cardboard square.

Front 26

Figure 4.1.17 shows the experimental set-up for a radiation experiment. The same sized black and white cardboard squares are attached to two thermometers close to an incandescent globe.State three variables that must be controlled to ensure a fair test.

Back 26

Variables to control include:
• the size of cardboard used
• the thickness of cardboard used
• the distance between the cardboard and the light source.

Front 27

Figure 4.1.17 shows the experimental set-up for a radiation experiment. The same sized black and white cardboard squares are attached to two thermometers close to an incandescent globe.Predict which thermometer will show the highest reading after 5 minutes.

Back 27

The thermometer behind the black cardboard

Front 28

Figure 4.1.17 shows the experimental set-up for a radiation experiment. The same sized black and white cardboard squares are attached to two thermometers close to an incandescent globe. Discuss reasons for your answer to question c.

Back 28

Dark-coloured objects are better absorbers of radiation than light-coloured objects. As such, the thermometer behind the black cardboard is expected to show the highest temperature reading after 5 minutes.

Front 29

Propose reasons why it is important for babies to wear a hat on a cool and windy day.

Back 29

Compared with an adult, a baby’s head is much larger relative to the size of the rest of their body. Usually a baby does not have much hair to act as an insulator to prevent heat loss from their head. Therefore, wearing a hat on a cool, windy day will provide additional insulation to protect the baby from getting too cold.

Front 30

You walk barefoot on carpet in the living room of your house and your feet feel warm, yet when you walk into the bathroom and stand on the ceramic tiles your feet feel cold. The carpet and tiles are at the same temperature. Propose an explanation for why this is the case.

Back 30

Although the carpet and ceramic tiles are at the same temperature, the ceramic tiles are a better conductor of heat than the carpet. Heat is conducted away from your feet, which are warmer than the tiles. As a result, your feet feel this loss of heat as cold. Your feet are insulated from heat loss by the carpet and feel warmer.

Front 31

On a hot day, you have a choice of travelling in a red car, a white car or a black car, all of the same model. All have been parked in the sunlight for three hours. Identify which car you would choose.

Back 31

The white car is the best choice.

Front 32

On a hot day, you have a choice of travelling in a red car, a white car or a black car, all of the same model. All have been parked in the sunlight for three hours. Justify your choice.

Back 32

Lighter colours reflect more infrared radiation than darker colours, which absorb more radiation. The white car should therefore have absorbed the least amount of infrared radiation and be slightly cooler than the other two cars.