Specific heat capacity

A student investigated the specific heat capacity of aluminium.

The student used an electric heater to increase the temperature of an aluminium block.

The student measured the:

• mass of the block

• energy transferred to the block

• temperature change of the block.

Table 2 shows the results.

Calculate the specific heat capacity of aluminium.

Use the Physics Equations Sheet.

Describe a method the student could have used to obtain the results in Table 2.

Wrapping the aluminium block in insulation makes the value for the specific heat capacity of aluminium more accurate.

Which are two reasons why?

Tick () two boxes.

A student investigated the specific heat capacity of aluminium.

The student used an electric heater to increase the temperature of an aluminium block.

The student measured the:

• mass of the block

• energy transferred to the block

• temperature change of the block.

Table 1 shows the results.

Calculate the specific heat capacity of aluminium.

Use the Physics Equations Sheet.

Describe a method the student could have used to obtain the results in Table 1.

Wrapping the aluminium block in insulation makes the value for the specific heat capacity of aluminium more accurate.

Which are two reasons why?

Tick () two boxes.

Figure 2 shows an outdoor swimming pool.

The water in the swimming pool comes from the sea.

The water in the pool is heated using a geothermal energy resource.

Which of the following describes a geothermal energy resource?

Tick (✓) one box.

15 kg of seawater is heated before it is added to the pool.

specific heat capacity of seawater = 3800 J/kg °C

Calculate the change in thermal energy of 15 kg of seawater when its temperature is increased by 9.0 °C.

Use the equation:

change in thermal energy = mass × specific heat capacity × temperature change

The energy transferred from 1.0 m² of the surface of the pool to the air is 80 J each second.

The surface area of the pool is 120 m².

Calculate the energy transferred from the whole surface of the pool to the air each second.

Which of the following units is the same as 1 J/s?

Tick (✓) one box.

The pool is above sea level.

5.0 kg of water is pumped from sea level into the pool.

The water gains 196 J of gravitational potential energy.

gravitational field strength = 9.8 N/kg

Calculate the height of the pool above sea level.

Use the equation:

The water in some swimming pools is heated by burning fossil fuels.

Explain one environmental disadvantage of burning fossil fuels.

Energy can be stored using a Compressed Air Energy Storage (CAES) system.

When more electricity is generated than is needed, a CAES system uses the surplus electricity to compress air in a storage tank.

When there is a greater demand for electricity, the CAES system releases the compressed air to generate electricity.

Figure 7 shows a diagram of the CAES system.

The CAES system has two processes:

• compressing air to store energy. This process has an efficiency of 0.72

• releasing the air to generate electricity. This process has an efficiency of 0.86

Calculate the efficiency of the CAES system.

Give your answer to 2 significant figures.

The generator works when forces from the compressed air cause a turbine to rotate.

When particles of air collide with the turbine they transfer energy to the turbine.

In warm weather the temperature of the compressed air increases, increasing the pressure inside the storage tank.

Explain how the motion of the particles in warmer air causes an increase in the power transferred to the turbine.

The volume of the storage tank is 5.0 × 10⁵ m³.

The density of the compressed air is 48 kg/m³.

specific heat capacity of air = 1100 J/kg °C

The temperature of the compressed air increases from 12 °C to 27 °C.

Calculate the energy transferred to the compressed air in the storage tank.

Use the Physics Equations Sheet.

Give your answer in standard form.

The UK government wants the amount of carbon dioxide released into the atmosphere to be reduced.

Explain why efficient energy storage is important in reducing the amount of carbon dioxide released when generating electricity.

A piece of steel is heated until it has all melted.

Calculate the change in thermal energy when the temperature of the piece of steel is increased by 50 °C.

mass of steel = 4.0 kg

specific heat capacity of steel = 420 J/kg °C

Use the equation:

change in thermal energy = mass × specific heat capacity × temperature change

The internal energy of the steel increases as the steel is heated.

What is meant by ‘internal energy of the steel’?

Tick (✓) one box.

Solid steel cannot be poured.

Which statement about the particles in a solid gives the reason why?

Tick (✓) one box.

Complete the sentence.

Choose the answer from the box.

Which diagram shows how the arrangement of particles changes when a solid melts and becomes a liquid?

Tick (✓) one box.

The density of steel decreases as it melts.

How does the spacing of the particles change as the steel melts?

Complete the sentence.

Choose the answer from the box.

Steel is a mixture of iron and a small amount of carbon.

Table 1 shows the mass of carbon in 1.0 kg of different types of steel.

A 4.0 kg piece of steel contains 18 grams of carbon.

Determine which type of steel the 4.0 kg piece is made from.

You should include a calculation in your answer.

The 4.0 kg piece of solid steel was heated until it reached its melting point.

The additional energy required to melt the piece of steel was 280 000 J.

Calculate the specific latent heat of fusion of the steel.

Use the Physics Equations Sheet.

Figure 12 shows a device that uses a mug of hot coffee to turn a wheel.

The hot coffee increases the temperature of the air in the chamber. Explain how the pressure in the chamber changes.

For the device to work, the air in the chamber must increase in temperature quickly. Explain why the bottom of the air chamber is made of metal rather than plastic.

The mass of air in the chamber is constant. What property of air allows a small change in internal energy to cause a large temperature change to the air in the chamber?

The changes in pressure in the air chamber cause the wheel to turn. Suggest one way to increase the speed at which the wheel turns.

The temperature of the coffee decreases as the device is used. The initial temperature of the coffee was 76 °C. The internal energy of the coffee decreased by 15 kJ.

specific heat capacity of coffee = 4200 J/kg °C Calculate the final temperature of the coffee. Use the Physics Equations Sheet.

A student made measurements to determine the specific heat capacity of vegetable oil.

Figure 10 shows the equipment used.

Describe how the student could use the equipment shown in Figure 10 to determine the specific heat capacity of vegetable oil.

Give one risk when using the equipment in Figure 10.

A different student did not have a joulemeter and calculated the energy transferred by the electric heater.

Use the Physics Equations Sheet to answer questions 06.3 and 06.4.

Write down the equation linking energy transferred (E), power (P) and time (t).

The electric heater had a power output of 50 watts.

Calculate the time taken for the electric element to transfer 4750 joules of energy to the vegetable oil.

In a deep fryer, vegetable oil is heated by an electric heating element. Food is then cooked in the hot vegetable oil.

The deep fryer contains an electrical component to monitor the temperature of the vegetable oil.

Figure 11 shows how the resistance of this electrical component changes with temperature.

What electrical component is used to monitor the temperature of the vegetable oil?

The electric heating element in the deep fryer automatically switches off when the vegetable oil reaches a certain temperature.

Figure 12 shows how the temperature of the vegetable oil changed after the deep fryer was switched on.

Determine the resistance of the electrical component when the electric heating element automatically switched off.

Use Figure 11 and Figure 12.

Some chips were put in the deep fryer.

In the deep fryer, water in the chips underwent a physical change and became steam.

Why is this a physical change?

Tick (✓) one box.

A student made measurements to determine the specific heat capacity of vegetable oil. Figure 2 shows the equipment used.

Describe how the student could use the equipment shown in Figure 2 to determine the specific heat capacity of vegetable oil.

Give one risk when using the equipment in Figure 2.

A different student did not have a joulemeter and calculated the energy transferred by the electric heater.

Use the Physics Equations Sheet to answer questions 02.3 and 02.4.

Write down the equation linking energy transferred (E), power (P) and time (t).

The electric heater had a power output of 50 watts. Calculate the time taken for the electric element to transfer 4750 joules of energy to the vegetable oil.

In a deep fryer, vegetable oil is heated by an electric heating element. Food is then cooked in the hot vegetable oil. The deep fryer contains an electrical component to monitor the temperature of the vegetable oil. Figure 3 shows how the resistance of this electrical component changes with temperature.

What electrical component is used to monitor the temperature of the vegetable oil?

The electric heating element in the deep fryer automatically switches off when the vegetable oil reaches a certain temperature. Figure 4 shows how the temperature of the vegetable oil changed after the deep fryer was switched on.

Determine the resistance of the electrical component when the electric heating element automatically switched off. Use Figure 3 and Figure 4.

Some chips were put in the deep fryer. In the deep fryer, water in the chips underwent a physical change and became steam. Why is this a physical change? Tick (✓) one box.

Solar intensity is a measure of the radiation received from the Sun at the surface of the Earth.

Figure 7 shows how the mean solar intensity changes with the distance from the equator.

The city of Athens is 4200 km from the equator.

What is the mean solar intensity in Athens?

Solar water heaters use radiation from the Sun to heat water.

The heated water is stored in a water tank.

Figure 8 shows a solar water heater on the roof of a building.

Cities closer to the equator have many more buildings with solar water heaters than cities further away from the equator.

Suggest why.

The use of solar water heaters may reduce the need to burn fossil fuels.

Complete the sentence.

Choose the answer from the box.

Burning fossil fuels contributes to global warming because there is an increase in

The efficiency of the solar water heater is 0.61

Calculate the useful power output when the total power input to the solar water heater is 1100 W.

Use the equation:

useful power output = efficiency × total power input

Different solar water heaters have different sized heating panels.

Suggest how the size of the heating panels affects the input power to a solar water heater.

Water has a high specific heat capacity.

What is meant by the specific heat capacity of water?

Tick (✓) one box.

The water tank contained 80 kg of water.

The change in thermal energy of the water was 8 400 000 J.

specific heat capacity of water = 4200 J/kg °C

Calculate the temperature change of the water.

Use the Physics Equations Sheet.

The water tank is thermally insulated.

How does thermal insulation affect the rate of energy transfer from the water in the tank?

Tick (✓) one box.

Table 1 shows information about different materials.

Which material in Table 1 is the best thermal insulator?

Tick (✓) one box.

An air source heat pump transfers energy from the air outside a building to increase the temperature of the air inside the building. Figure 13 shows an air source heat pump.

The compressor is connected to the mains electricity supply. The pipe in the heat pump contains a substance called coolant. In the evaporator, energy is transferred from the air outside the building to the liquid coolant. The temperature of the coolant increases and it evaporates.

Explain what happens to the internal energy of the coolant as its temperature increases.

What name is given to the energy needed to change the state of the liquid coolant?

What happens to the mass of the coolant as it evaporates and becomes a vapour? Tick (✓) one box.

The compressor increases the density and temperature of the coolant vapour inside the pipe. Explain why the pressure in the pipe increases.

The condenser transfers energy from the coolant to the air in the building. When the total energy input to the heat pump system is 1560 kJ the temperature of the air in the building increases from 11.6 °C to 22.1 °C. The efficiency of the heat pump system is 87.5%. The mass of the air inside the building is 125 kg. Calculate the specific heat capacity of the air in the building. Give your answer in standard form.

The air in the building gains 400 J for every 100 J of energy transferred from the mains electricity supply to the compressor. An advertisement claims that the heat pump system has an efficiency of 400%. Explain why the advertisement is not correct.

A scientist had a balloon which was filled with air.

Which statement describes how air particles move? Tick (✓) one box.

The temperature of the air was 19 °C The scientist dipped the balloon into liquid nitrogen. The temperature of the liquid nitrogen was −196 °C

Which thermometer could be used to measure the temperature of the liquid nitrogen? Tick (✓) one box.

The scientist wore special insulating gloves when putting the balloon into the liquid nitrogen. Suggest why.

When the balloon was put into liquid nitrogen the temperature of the air in the balloon decreased. Complete the sentences. Choose answers from the box. Each answer may be used once, more than once or not at all.

As the air in the balloon cooled down, the speed of the particles

The air in the balloon had a mass of 0.00320 kg The temperature of the air in the balloon decreased by 215 °C The change in thermal energy of the air in the balloon was 860 J Calculate the specific heat capacity of the air in the balloon. Use the Physics Equations Sheet.

The liquid nitrogen boiled. What happens to the temperature of nitrogen as it boils?

Tick (✓) one box.

The scientist recorded measurements to calculate the specific latent heat of vaporisation of nitrogen.

What is meant by vaporisation? Tick (✓) one box.

The mass of nitrogen that vaporised was 0.0072 kg 1440 J of energy was transferred to the nitrogen as it vaporised. Calculate the specific latent heat of vaporisation of nitrogen. Use the Physics Equations Sheet.

Ice cream is made by cooling a mixture of liquid ingredients until they freeze.

Which statement describes the motion of the particles in solid ice cream? Tick (✓) one box.

How do the kinetic energy and the potential energy of the particles change as a liquid

Figure 6 shows a bowl used for making ice cream.

The walls of the bowl contain a liquid coolant. The bowl is cooled to –20 °C before the mixture is put in the bowl. The bowl causes the mixture to cool down and freeze.

Explain why the different thermal conductivities of metal and plastic are important in the design of the bowl.

The liquid coolant has a freezing point below –20 °C Explain one other property that the liquid coolant should have.

The initial temperature of the mixture was +20 °C. The mixture froze at –1.5 °C. A total of 165 kJ of internal energy was transferred from the mixture to cool and freeze it. specific heat capacity of the mixture = 3500 J/kg °C specific latent heat of fusion of the mixture = 255 000 J/kg

Calculate the mass of the mixture. Give your answer to 2 significant figures.

A student investigated how the mass of water in an electric kettle affected the time taken for the water to reach boiling point. The kettle switched off when the water reached boiling point. Figure 4 shows the kettle.

The heating element of the kettle was connected to the mains supply. Explain why the temperature of the heating element increased.

Give one variable that the student should have controlled.

Figure 5 shows how the mass of water in the kettle affected the time taken for the kettle to switch off.

Suggest why the line on Figure 5 does not go through the origin.

Suggest why the results give a non-linear pattern.

The power of the kettle was 2.6 kW The kettle took 120 seconds to heat 0.80 kg of water from 18 °C to 100 °C Calculate the specific heat capacity of water using this information. Give your answer to 2 significant figures.

Radioactive nuclei can emit alpha, beta or gamma radiation.

Which type of radiation is the most penetrating?

Tick one box.

Which type of radiation is the most ionising?

Tick one box.

Which type of radiation has the longest range in air?

Tick one box.

When radioactive isotopes in the Earth’s crust decay they release energy.

The decay causes the heating of rocks in the crust.

Figure 8 shows the decay of uranium–238 (U–238) into thorium–234 (Th–234).

Figure 8

Complete Table 2 to show the number of neutrons and protons in the nuclei.

Geothermal power stations pump water through heated rocks.

The temperature of the water increases from 20 °C to its boiling point of 100 °C

Calculate the change in thermal energy when the mass of water heated is 150 kg

Specific heat capacity = 4 200 J/kg °C

Use the Physics Equations Sheet.