Internal energy

A teacher had a conical flask containing a gas.

How are the particles arranged in a gas?

Tick (✓) one box.

Particles are all touching each other.

Particles are arranged in a pattern.

Particles are arranged randomly.

How do the particles move in a gas?

Tick (✓) one box.

Particles move at the same speed.

Particles move in circular paths.

Particles move randomly.

The teacher demonstrated how gas pressure varies with temperature.

Figure 1 shows the apparatus used.

The Bunsen burner transferred thermal energy to the water.

The change in thermal energy of the water was 31 500 J.

The mass of water in the beaker was 0.25 kg.

Calculate the temperature increase of the water.

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

Use the equation:

When the temperature of the gas in the conical flask increased, the gas pressure in the conical flask increased.

How did increasing the temperature affect the mean speed of the gas particles?

How did increasing the temperature affect the mean kinetic energy of the gas particles?

A teacher demonstrated how gas pressure varies with temperature.

Figure 7 shows the apparatus used.

The thermal energy transferred to the water by the Bunsen burner was 63 kJ.

The water temperature changed from 22 °C to 82 °C.

Calculate the mass of water in the beaker.

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

Use the Physics Equations Sheet.

Increasing the temperature of the gas in the conical flask affected the gas pressure in the conical flask.

Explain why.

What name is given to the energy stored by the particles in a system?

A student investigated the heating of some wax.

This is the method used.

1. Put a cube of wax in a beaker.

2. Place the beaker on a heater connected to a joulemeter.

3. Turn on the heater.

4. When the wax begins to melt, turn on the joulemeter.

5. When all the wax has melted, record the reading shown on the joulemeter.

Figure 2 shows the arrangement.

The mass of the cube of wax was 0.15 kg.

The energy transferred to melt the wax was 31 500 J.

Calculate the specific latent heat of fusion of wax.

Use the equation:

Choose the unit from the box.

Not all of the energy transferred by the heater was used to melt the wax.

What happened to the energy that was not used to melt the wax?

Tick (✓) one box.

The energy decreased the temperature of the wax.

The energy increased the mass of the wax.

The energy was transferred to the surroundings.

Which two of the following would increase the accuracy of the student’s results?

Tick (✓) two boxes.

Completing the investigation in a colder environment.

Insulating the sides of the beaker that the wax was in.

Stirring the wax as it was melting.

Using a beaker with a larger volume.

Using a smaller mass of wax.

The student continued to heat the wax after it had melted.

The student measured the temperature of the wax every 10 seconds.

Figure 3 shows how the temperature of the liquid wax varied with time.

What was the temperature change between 0 seconds and 80 seconds?

Tick (✓) one box.

12 °C 70 °C 82 °C

Between 0 seconds and 80 seconds, 3600 J of energy was transferred to the wax.

The mass of wax was 0.15 kg.

Calculate the specific heat capacity of the wax using the student’s data.

Use your answer to Question 02.4 and the equation:

Specific heat capacity = __________________________ J/kg °C

A student investigated the heating of some wax.

This is the method used.

1. Put a cube of wax in a beaker.

2. Place the beaker on a heater connected to a joulemeter.

3. Turn on the heater.

4. When the wax begins to melt, turn on the joulemeter.

5. When all the wax has melted, record the reading shown on the joulemeter.

Figure 10 shows the arrangement.

The student made these measurements:

mass of the cube of wax = 0.15 kg

energy transferred to melt the wax = 33 kJ

Calculate the specific latent heat of fusion of wax using the student’s measurements.

Use the Physics Equations Sheet.

The student’s value for specific latent heat of fusion is not accurate because some energy was dissipated to the surroundings.

Explain how the dissipation of energy affected the student’s calculated value.

The student continued to heat the wax after it had melted.

The student measured the temperature of the wax every 10 seconds.

Figure 11 shows how the temperature of the wax varied with time.

Between 0 seconds and 80 seconds, 4950 J of energy was transferred to the wax.

The mass of the wax was 0.15 kg.

Determine the specific heat capacity of the wax.

Use the Physics Equations Sheet.

Specific heat capacity = __________________________ J/kg°C

Heaters can be used to heat homes and gardens.

Gas heaters can be used to heat gardens.

The gas is stored in a container with a fixed volume.

Figure 10 shows a gas heater.

On a sunny day the burner is not lit.

The temperature of the gas in the container increases.

Complete Table 3.

Put one tick (✓) in each row.

Figure 11 shows an electric heater.

The heater is filled with a liquid.

When the heater is switched on, the temperature of the liquid in the heater increases.

On one day, the starting temperature of the liquid was 15.0 °C.

The final temperature of the liquid was 57.5 °C.

What was the temperature change of the liquid?

The change in thermal energy of the liquid in the heater was 892 500 J.

What was the change in thermal energy of the liquid in kJ?

1000 J = 1 kJ

On another day, the temperature change of the liquid was 45.0 °C.

The mass of liquid in the heater is 5.0 kg.

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

Calculate the change in thermal energy of the liquid in the heater in joules.

Use the equation:

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

The liquid in the heater was replaced with a new liquid.

The new liquid had a greater specific heat capacity.

What happened to the energy required to increase the temperature of the liquid in the heater by 1 °C?

Tick (✓) one box.

The energy required decreases.

The energy required stays the same.

The energy required increases.

Figure 6 shows an electric heater.

This type of heater is filled with a liquid.

The heater contained 5.0 kg of water.

When the heater was switched on, the temperature of the water in the heater increased to 75 °C.

The change in thermal energy of the water was 1260 kJ.

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

Calculate the starting temperature of the water in the heater.

Use the Physics equations sheet.

An identical heater contains 5.0 kg of oil instead of 5.0 kg of water.

specific heat capacity of oil = 1970 J/kg °C

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

Explain the difference in the energy needed to cause the same temperature change in the oil and in the water.

Gas heaters may be used to heat gardens.

The gas is stored in a container with a fixed volume.

Figure 7 shows a gas heater.

On a sunny day the burner is not lit.

The temperature of the gas in the container increases.

Explain why the pressure inside the container changes.

Different substances change state at different temperatures.

Table 1 shows the melting points and boiling points of three substances.

What is the state of sodium at 90 °C?

Tick (✓) one box.

Gas

Liquid

Solid

Complete the sentence.

Choose the answer from the box.

Sodium chloride is a liquid at ___________________ °C.

A student investigated the boiling point of different concentrations of sodium chloride solutions.

Figure 3 shows the apparatus.

This is the method used.

1. Add 100 cm³ of water to a beaker.

2. Add 10 g of sodium chloride to the water.

3. Heat the beaker until the solution boils.

4. Record the boiling point of the solution.

5. Repeat steps 1 to 4 with different masses of sodium chloride.

Figure 4 shows the results.

Determine the difference between the boiling point of the solution using:

and

Use Figure 4.

Boiling point using 15 g of sodium chloride ________________ °C

Boiling point using 30 g of sodium chloride ________________ °C

Describe the pattern of the results in Figure 4.

Include data from Figure 4 in your answer.

The student heated water at its boiling point until all the liquid water changed to water vapour.

mass of water = 0.20 kg specific latent heat of vaporisation of water = 2 260 000 J/kg

Calculate the energy required to change the liquid water into water vapour.

Use the equation:

energy for the change of state = mass × specific latent heat of vaporisation

Choose the unit from the box.

Boiling water can be used to cook food.

Food can be cooked in a pressure cooker.

Figure 5 shows a pressure cooker.

What will happen to the water particles as the temperature of the water increases?

Tick (✓) one box.

The kinetic energy of the particles will decrease.

The particles will hit each other less often.

The particles will move faster.

The pressure inside the pressure cooker changes during heating.

Table 2 shows the boiling point of the water in the pressure cooker at different pressures.

What happens to the boiling point of the water as the pressure in the pressure cooker increases?

Use Table 2.

Figure 6 shows a saucepan.

The boiling point of water in a saucepan is 100 °C.

Explain one advantage of using a pressure cooker instead of a saucepan to cook food.

Matter can exist in different states.

Table 7 shows the melting points and boiling points of four substances.

Give the temperature at which nitrogen condenses.

Nitrogen gas is transported in cylinders at high pressure.

Figure 10 shows a cylinder containing nitrogen gas.

What causes the pressure on the inside walls of the gas cylinder?

Carbon dioxide sublimates.

What happens when carbon dioxide sublimates?

Use Table 7.

Solid carbon dioxide is used during the transport of frozen food.

Using solid carbon dioxide keeps the food cold for longer than using frozen water.

Suggest one other advantage of using solid carbon dioxide instead of using frozen water during the transport of frozen food.

The planet Saturn has a moon called Titan.

The surface temperature of Titan is −179.6 °C.

Features similar to rivers have been seen on Titan.

Which substance in Table 7 could be the liquid in the rivers on Titan?

Figure 11 shows a simple model which can be used to describe changes of state.

Give two limitations of using this model to describe changes of state.

Some water at 15 °C is heated until it all turns to steam at 100 °C.

The total energy supplied to the water is 1 320 000 J.

mass of water = 500 g specific heat capacity of water = 4200 J/kg °C

Calculate the specific latent heat of vaporisation of water.

Use the Physics Equations Sheet.

A student investigated how the temperature of water changed as it was heated.

Figure 2 shows some of the apparatus used.

The student switched the heater on then recorded the temperature of the water every 5 minutes.

Table 1 shows the results.

What was the resolution of the thermometer used in the investigation?

Use Table 1.

Tick (✓) one box.

0.1 °C 1 °C 10 °C
100 °C

Calculate mean value X in Table 1.

Draw a ring around the anomalous result in Table 1.

What should the student have done with the anomalous result?

Give two ways to reduce energy transfer from the apparatus to the surroundings.

The water in the beaker had a mass of 0.20 kg.

The temperature increase of the water was 33 °C.

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

Calculate the change in thermal energy of the water.

Use the equation:

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

Choose the unit from the box.

Explain what happens to the mass of water in the beaker during a test.

A student investigated the heating of a copper block.

An electric heater and a thermometer were inserted into holes in the copper block.

Figure 4 shows the apparatus used.

The joulemeter measured the energy transferred to the electric heater.

Every minute, the student recorded: the temperature of the copper block the energy transferred to the electric heater.

Figure 5 shows the results.

Draw a line of best fit on Figure 5.

What conclusion can be made from Figure 5 ?

The student calculated the specific heat capacity of copper using the final temperature of the copper block.

The copper block was not insulated.

Explain why the student’s calculated value of specific heat capacity was higher than expected.

Computer components get hot when they are in use.

To prevent components overheating, energy is transferred from the components to a heat sink made of metal.

Metal heat sinks can be different shapes and have different types of surface.

Figure 6 shows four metal heat sinks.

A student investigated the thermal energy transfer from the four heat sinks.

The heat sinks were all made of the same metal and had the same mass.

This is the method used.

1. Place heat sink A in an oven and heat until the temperature of the heat sink reaches 100 °C.

2. Remove the heat sink from the oven.

3. Record the time taken for the heat sink to cool to room temperature.

4. Repeat steps 1 to 3 for heat sinks B, C and D.

Table 5 shows the results.

Explain two features of heat sink D that make it the best to prevent a computer component overheating.

A computer component transfers 89 J of energy to a copper heat sink.

The mass of the copper heat sink is 5.0 g.

The starting temperature of the copper heat sink is 20 °C.

specific heat capacity of copper = 386 J/kg °C

Calculate the final temperature of the copper heat sink.