Specific latent heat

A scientist poured some liquid nitrogen into a container.

The container was then sealed.

Figure 10 shows the container.

The liquid nitrogen was at its boiling point.

When 9950 J of thermal energy was transferred to the liquid nitrogen, 50 g of the nitrogen turned into a gas.

Calculate the specific latent heat of vaporisation of nitrogen.

Use the Physics Equations Sheet.

Explain how the internal energy of the nitrogen changed as the nitrogen turned from a liquid to a gas.

After the nitrogen had boiled, the temperature of the gas increased.

Explain how the pressure in the container changed as the temperature increased.

An electrical appliance is connected to the mains electricity supply using a three-core cable.

Figure 13 shows a three-core cable.

What colour is the insulation covering the live wire inside the cable?

Tick () one box.

What colour is the insulation covering the neutral wire inside the cable?

Tick () one box.

The plug connected to the cable contains a fuse.

A fuse contains a wire that is designed to melt when the current is too great.

What is the circuit symbol for a fuse?

Tick () one box.

The wire in the fuse melts when there is a charge flow of 2.0 C in a time of 0.40 s.

Calculate the current in the wire when it melts.

Use the equation:

The mass of the wire is 0.016 g.

specific latent heat of fusion of the wire = 60 000 J/kg

Calculate the change in thermal energy needed to melt the wire.

Use the Physics Equations Sheet.

The fuse transfers some energy to the surroundings as it melts.

How does transferring energy to the surroundings affect the total energy needed to melt the fuse?

Tick () one box.

The live wire in a three-core cable is connected to a fuse inside a plug.

A fuse contains a wire that is designed to melt when the current gets too great.

Figure 17 shows a fuse.

What colour is the insulation covering the live wire in a three-core cable?

Draw the circuit symbol for a fuse in the box below.

The fuse wire melts when there is a charge flow of 2.0 C for 400 ms.

Calculate the current in the fuse wire.

Use the Physics Equations Sheet.

When the fuse wire is at its melting point, the additional energy needed to melt the wire is 1.02 J.

specific latent heat of fuse wire = 60 kJ/kg

Calculate the mass of the fuse wire.

Use the Physics Equations Sheet.

The calculation in Question 10.4 assumes there is no energy transferred to the surroundings.

How would the time taken for the wire to melt be affected if some energy was transferred to the surroundings?

Give a reason for your answer.

Tick (✓) one box.

Figure 14 shows an electrical circuit used to heat the windscreen of a car.

Each resistor in the circuit represents a heating element.

The 12 V battery supplies direct potential difference.

What is meant by ‘direct potential difference’?

Use the Physics Equations Sheet to answer questions 10.2 and 10.3.

Which equation links charge flow (Q), energy (E) and potential difference (V)?

Tick (✓) one box.

Calculate the charge flow through the 12 V battery when the battery transfers 5010 J of energy.

Ice forms on the windscreen at a temperature of 0 °C.

The electrical circuit transfers 5010 J of energy to the ice.

A mass of 0.015 kg of ice melts.

Calculate the specific latent heat of fusion of water.

Use the Physics Equations Sheet.

The electrical circuit was left switched on while the ice changed from a solid to a liquid and increased in temperature to 5 °C.

Explain the changes in the arrangement and movement of the particles as the ice melted and the temperature increased to 5 °C.

Figure 4 shows an electrical circuit used to heat the windscreen of a car. Each resistor in the circuit represents a heating element.

The 12 V battery supplies direct potential difference. What is meant by ‘direct potential difference’?

Use the Physics Equations Sheet to answer questions 03.2 and 03.3.

Which equation links charge flow (Q), energy (E) and potential difference (V)? Tick (✓) one box.

Calculate the charge flow through the 12 V battery when the battery transfers 5010 J of energy.

Ice forms on the windscreen at a temperature of 0 °C. The electrical circuit transfers 5010 J of energy to the ice. A mass of 0.015 kg of ice melts. Calculate the specific latent heat of fusion of water. Use the Physics Equations Sheet.

The electrical circuit was left switched on while the ice changed from a solid to a liquid and increased in temperature to 5 °C. Explain the changes in the arrangement and movement of the particles as the ice melted and the temperature increased to 5 °C.

A student determined the specific latent heat of vaporisation of water.

Figure 6 shows some of the equipment used.

The student measured a mass of water and put it into the beaker.

What measuring instrument should the student have used to measure the mass of the water?

Tick (✓) one box.

The power output of the heater stayed the same throughout the experiment.

What type of variable was the power output of the heater?

Tick (✓) one box.

The student turned on the heater and heated the water until it reached boiling point.

The student continued to heat the water so that it boiled for several minutes.

The mass of the water remaining in the beaker was measured again.

Give one way the beaker of boiling water could be moved safely to measure its new mass.

The mass of water that turned into steam was 0.0090 kg.

The heater transferred 25 200 J of energy to the water to turn it into steam.

Calculate the specific latent heat of vaporisation of water given by the student’s data.

Use the Physics Equations Sheet.

Choose the unit from the box.

What was a source of error in the student’s experiment?

Tick (✓) one box.

A student determined the specific latent heat of vaporisation of water. Figure 9 shows some of the equipment used.

This is the method used:

1. Put 50 cm³ of water in a beaker.

2. Measure the mass of the beaker and water.

3. Use a heater to boil the water and keep it boiling for 600 seconds.

4. Measure the mass of the beaker and water after 600 seconds.

What measuring instrument should be used to measure the volume of water?

What is a hazard in the student’s investigation?

The initial mass of the beaker and water was 0.080 kg. The final mass of the beaker and water was 0.071 kg. The energy transferred by the immersion heater as the water boiled was 25 200 J. Calculate the specific latent heat of vaporisation of water given by the student’s data. Give the unit. Use the Physics Equations Sheet.

Some thermal energy was transferred to the surroundings while the water was being heated. Explain how this affected the student’s value for the specific latent heat of vaporisation of water.

Some of the water evaporated before its temperature reached 100 °C. Explain how this affected the student’s value for the specific latent heat of vaporisation of water.

A student investigated the three states of matter.

The arrangement of particles in the three states of matter are different.

Draw one line from each particle arrangement to the state of matter.

A large lump of ice was heated and changed state.

Figure 1 shows how the temperature varied with time.

Which part of Figure 1 shows when the ice was melting?

Tick (✓) one box.

Which part of Figure 1 shows when the water was boiling?

Tick (✓) one box.

Which property of the water particles changes as the temperature of the water increases?

Tick (✓) one box.

Calculate the thermal energy needed to melt 0.250 kg of ice at 0 °C.

specific latent heat of fusion of water = 334 000 J/kg

Use the equation:

thermal energy = mass × specific latent heat

Complete the sentence.

Choose the answer from the box.

A substance is heated and changes directly from a solid to a gas.

A student investigated how the temperature of a lump of ice varied as the ice was heated. The student recorded the temperature until the ice melted and then the water produced boiled. Figure 17 shows the student’s results. The power output of the heater was constant.

The specific heat capacity of ice is less than the specific heat capacity of water. Explain how Figure 17 shows this.

The specific latent heat of fusion of ice is less than the specific latent heat of vaporisation of water. Explain how Figure 17 shows this.

A second student did the same investigation and recorded the temperature until the water produced boiled. In the second student’s investigation more thermal energy was transferred to the surroundings. Describe two ways the results of the experiment in Figure 17 would have been different.

The energy transferred to the water was 69 kJ. Calculate the specific latent heat of vaporisation of water. Give the unit.

A student heated water in an electric kettle.

Water has a high specific heat capacity. Complete the sentence. Choose answers from the box.

The specific heat capacity of a substance is the energy needed to raise the

The kettle circuit contains a thermistor which is used to switch the kettle off when the water reaches 100 °C. What is the correct symbol for a thermistor? Tick (✓) one box.

The resistance of the heating element in the kettle is 15 Ω. The current in the heating element is 12 A. Calculate the power of the heating element. Use the equation: power = (current)² resistance

The student investigated how quickly the kettle could increase the temperature of 0.50 kg of water. Figure 10 shows the results of the investigation.

The temperature of the water did not start to increase until 10 seconds after the kettle was switched on. What is the reason for this? Tick (✓) one box.

Describe a method the student could have used to obtain the results shown in Figure 10.

The mass of water in the kettle was 0.50 kg. The temperature of the water increased from 20 °C to 100 °C. specific heat capacity of water = 4200 J/kg °C Calculate the energy transferred to the water. Use the Physics Equations Sheet.

The water in the kettle boiled for a short time before the kettle switched off. During this time 5.0 g of water changed to steam. specific latent heat of vaporisation of water = 2 260 000 J/kg Calculate the energy transferred to change the water to steam. Use the Physics Equations Sheet.

Figure 1 shows water being heated. Eventually the water changed into steam.

Complete the sentences. Choose answers from the box. Each answer may be used once, more than once or not at all.

distance between the particles in liquid water.

Figure 2 shows how the temperature of the water varied with time.

What is the name of the process that is taking place between points A and B ? Give a reason for your answer.

A mass of 0.063 kg of water was turned into steam. The specific latent heat of vaporisation of water is 2 260 000 J/kg

Calculate the thermal energy transferred to the water to turn it into steam. Use the equation: thermal energy for a change of state = mass × specific latent heat

The mass of the steam was 0.063 kg The volume of the steam was 0.105 m³

Calculate the density of steam. Use the equation:

Choose the unit from the box.

A student investigated the thermal conductivity of different metals.

This is the method used:

1. Measure the mass of an ice cube.

2. Put the ice cube on a metal block which is at room temperature.

3. Measure the mass of the ice cube after one minute.

4. Repeat with other blocks of the same mass made from different metals.

Table 3 shows the student’s results.

The initial temperature of each ice cube was –15 °C

Why was it important that the initial temperature of each ice cube was the same?

Tick (✓) one box.

Which metal had the highest thermal conductivity?

Give a reason for your answer.

Suggest one source of random error in the student’s investigation.

An ice cube has a temperature of –15.0 °C

The total thermal energy needed to raise the temperature of this ice cube to 0.0 °C and completely melt the ice cube is 5848 J

specific heat capacity of ice = 2100 J/kg °C specific latent heat of fusion of ice = 334 000 J/kg

Calculate the mass of the ice cube.

Figure 14 shows a Bunsen burner heating some water in a beaker. Eventually the water changes into steam.

Explain how the internal energy of the water changes as it is heated from 20 °C to 25 °C

How is the particle model used to explain the difference in density between a liquid and a gas?

Tick (✓) one box.

A student measured the mass of boiling water that was turned into steam in five minutes.

Explain how the student could use this information to estimate the power output of the Bunsen burner in watts.

The plug of an electrical appliance contains a fuse.

What is the correct circuit symbol for a fuse?

Tick one box.

The appliance is connected to the mains electrical supply. The mains potential difference is 230 V.

Calculate the energy transferred when 13 C of charge flows through the appliance.

Use the equation:

energy transferred = charge flow × potential difference

Figure 9 shows the structure of a fuse.

Write down the equation that links charge flow, current and time.

The fuse wire melts when 1.52 coulombs of charge flows through the fuse in 0.40 seconds.

Calculate the current at which the fuse wire melts.

The mass of the fuse wire is 0.00175 kg. The specific latent heat of fusion of the fuse wire is 205 000 J/kg.

Calculate the energy needed to melt the fuse wire.

Use the Physics Equations Sheet.