Specific heat capacity

Which of these describes the motion of particles in a liquid?

A student is asked to find the density of a metal key.

Figure 8 shows a metal key and some apparatus.

Using the apparatus shown in Figure 8, describe how the student can find the density of the metal key.

A student heats an aluminium block, as shown in Figure 9.

The aluminium block has a mass of 0.96 kg.

The specific heat capacity of aluminium is 920 J / kg °C.

The temperature of the block increases from 18 °C to 35 °C.

Calculate the change in thermal energy of the aluminium block.

Use the equation

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

change in thermal energy =_........

Suggest one way the student could reduce the energy loss from the aluminium block during the experiment.

The thermometer does not show the maximum temperature reached by the aluminium block until some time after the heater is switched off.

Give one reason for this.

A teacher heats a block of wax until all the wax melts.

The teacher pours the melted wax into a container and allows the wax to cool.

Figure 7 shows how the temperature of the wax changes during a time of 20 minutes.

Four different points on the graph are labelled P, Q, R and S.

Between which two points is all the wax liquid?

Describe the change in the motion of the wax particles as the wax changes from liquid to solid.

Figure 8 shows the values of some properties of the wax.

The wax has a mass of 3.9 kg.

Using information from Figure 8, calculate the volume of the wax when it is all liquid.

Use the equation

volume =_........ ³

State, using information from Figure 8, how the volume of the wax changes when it becomes a solid.

Explain why, using Figure 8, the time from R to S is much shorter than the time from Q to R on the graph in Figure 7.

Figure 14 shows a saucepan of milk being heated on an electric cooker.

Figure 14

Figure 15 is a table of data about the milk being heated.

Using data from the table in Figure 15, calculate the increase in temperature of the milk.

increase in temperature =_........

Using data from the table in Figure 15, calculate the specific heat capacity of the milk.

Use the equation

specific heat capacity =_........ J/kg °C

The cooker supplies 130 000 J of energy in a time of 87 s.

Calculate the power supplied by the cooker.

Use the equation

Give your answer to 2 significant figures.

power =_........

The cooker supplies 130 000 J of energy but only 96 000 J of this energy is used to heat the milk.

Calculate the efficiency of heating the milk using this cooker.

Use the equation

The wiring for the cooker has safety features.

Which of these wires would help to protect a person from getting an electric shock if a fault developed in the cooker?

Explain how a fuse can prevent overheating of the wiring for the cooker.

Which of these changes of state describes sublimation?

Figure 21 shows a sealed aerosol can.

The sealed can is taken from a cold room into a warm room.

If the volume of the can remains the same, which of these does not change?

Figure 22 shows a storage heater.

The storage heater contains bricks.

The bricks are heated electrically.

The electrical heater supplies 210 kJ of energy to each brick in the storage heater.

One brick has a mass of 5.8 kg.

The specific heat capacity for the brick is 860 J/kg K.

Use this data to calculate the increase in temperature of the brick.

temperature increase =_........

The actual temperature increase will be smaller than you calculated in (i).

Explain why the actual temperature increase will be smaller than the value in (i).

* (d) Describe an investigation to determine the value for the specific heat capacity of water.

Your answer should include details of

• the apparatus needed

• the experimental procedure

• how the value may be calculated from the measurements taken.

You may draw a diagram to help your answer.

Figure 5 shows the apparatus used to investigate the melting of some crushed ice.

Suggest one safety precaution needed when using the electrical heater.

Suggest one way of heating the crushed ice without using electricity.

Figure 6 shows a graph produced from the data collected by the data logger in Figure 5.

Labels P, Q, R and S have been added.

At the start, P, the beaker contains crushed ice at –8C.

Describe what happens to the crushed ice during the next 15 minutes.

You may use labels P, Q, R and S to help your answer.

Figure 7 shows bubbles of air that a diver breathes out.

The bubbles rise towards the surface.

Which row of the table is correct as one bubble rises?

Which of these is a unit of pressure?

The diver measures air pressure in atmospheres.

A bubble has an initial volume, V₁, of 0.50 litres, at a pressure, P₁, of 3.30 atmospheres.

The bubble rises towards the surface of the water, where the pressure, P₂, is 1.07 atmospheres.

Calculate the volume, V₂, of the bubble near the surface.

Use the equation

volume, V₂, of the bubble =_........

When water boils and turns into steam, there are changes in the arrangement of particles and the density.

Which of these shows the changes?

Figure 21 shows some water in a measuring cylinder and a lump of iron.

The lump of iron is lowered fully into the water.

The water level in the measuring cylinder rises to 530 cm³.

The density of iron is 7.9 g / cm³.

Calculate the mass of the lump of iron.

Use the equation

Give your answer to 2 significant figures.

A piece of wood has a similar shape and volume to the lump of iron.

The density of the wood is 0.82 g / cm³.

The density of water is 1.00 g / cm³

Explain why the method used in part (b) cannot be used to determine the mass of the piece of wood.

*(d) A student needs to determine the specific heat capacity of water.

Figure 22 shows some of the equipment the student uses.

Describe the method the student should use to determine the specific heat capacity of water.

Your description should include, with reasons,

• any other equipment needed

• the measurements needed.

You may draw a diagram if it helps your answer.

Explain the difference between the term ‘specific heat capacity’ and the term ‘specific latent heat’ when applied to heating substances.

Figure 19 shows some apparatus that may be used to determine the specific heat capacity of water.

A student measures the initial temperature of the water.

The power supply is switched on for 10 minutes and then switched off.

Explain how the student should then obtain an accurate reading for the final temperature of the water, to be used in the calculation of the specific heat capacity.

*(c) A container of gas is at room temperature.

The gas is then heated.

The volume of the container remains the same.

By considering changes in velocities of the gas particles, explain how the temperature increase affects

• the average kinetic energy of the particles

• the pressure the particles exert on the walls of the container.

An electric kettle contains 1.41 kg of water at 25 °C.

The kettle is switched on.

After a while, the water reaches boiling point at 100 °C.

The specific heat capacity of water is 4200 J / kg °C.

Calculate the amount of thermal energy supplied to the water by the kettle. Give your answer to the appropriate number of significant figures.

Use an equation selected from the list of equations at the end of the paper.

The kettle is kept switched on and the water continues to boil.

After a while, the mass of the water in the kettle has decreased to 1.21 kg.

The thermal energy supplied to the water during this time was 450 000 J.

Calculate the specific latent heat of vaporisation of water.

Use an equation selected from the list of equations at the end of the paper.

Figure 19 shows a small piece of copper about 3 cm high.

A student wants to determine the density of copper.

The student uses a balance to measure the mass of the piece of copper.

Explain how the student could measure the volume of the piece of copper.

The mass of the piece of copper is 0.058 kg.

The volume of the piece of copper is 6.510^–6m³.

Calculate the density of copper.

A student wants to determine the specific heat capacity of copper.

Figure 20 shows a piece of copper, with a thread tied around it, in a glass beaker of boiling water.

The student leaves the piece of copper in the boiling water so that the copper reaches a temperature of 100C.

The student uses the thread to take the piece of copper out of the boiling water.

The student puts the hot piece of copper into a different beaker of cold water at 20C.

The apparatus is shown in Figure 21.

The student assumes that the thermal energy gained by the water equals the thermal energy lost by the piece of copper.

The water and copper both reach a temperature of 22C.

The cold water gains 1050 J of energy.

The mass of the piece of copper is 0.058 kg.

Calculate a value for the specific heat capacity of copper, using these results.

Use the equation

change in thermal energy = massspecific heat capacitychange in temperature

The value for the specific heat capacity of copper obtained from the student’s results is lower than the correct value.

State two ways that the experiment could be improved to give a value that is closer to the correct value.

A long piece of wire is made into a coil as shown in Figure 22.

The coil is connected to a low voltage power supply.

Describe how this coil could be used instead of the Bunsen burner in Figure 20.

Figure 4 shows a small piece of copper about 3 cm high.

A student wants to determine the density of copper.

The student uses a balance to measure the mass of the piece of copper.

Explain how the student could measure the volume of the piece of copper.

The mass of the piece of copper is 0.058 kg.

The volume of the piece of copper is 6.5×10^–6m³.

Calculate the density of copper.

A student wants to determine the specific heat capacity of copper.

Figure 5 shows a piece of copper, with a thread tied around it, in a glass beaker of boiling water.

The student leaves the piece of copper in the boiling water so that the copper reaches a temperature of 100C.

The student uses the thread to take the piece of copper out of the boiling water.

The student puts the hot piece of copper into a different beaker of cold water at 20C.

The apparatus is shown in Figure 6.

The student assumes that the thermal energy gained by the water equals the thermal energy lost by the piece of copper.

The water and copper both reach a temperature of 22C.

The cold water gains 1050 J of energy.

The mass of the piece of copper is 0.058 kg.

Calculate a value for the specific heat capacity of copper, using these results.

Use the equation

change in thermal energy = massspecific heat capacity×change in temperature

The value for the specific heat capacity of copper obtained from the student’s results is lower than the correct value.

State two ways that the experiment could be improved to give a value that is closer to the correct value.

Solid, liquid and gas are states of matter.

Which process describes the change from a solid to a liquid?

A student determines the density of a liquid.

The student puts an empty measuring cylinder on a balance (Figure 10a). The student then adds liquid to the measuring cylinder (Figure 10b).

Calculate the mass of liquid added and the volume of liquid added.

Use the information in Figures 10a and 10b.

mass of liquid added =_........ g

volume of liquid added =_........ cm³

Which equation should the student use to calculate the density of the liquid?

State two improvements the student could make to this investigation.

Figure 11 shows an electric kettle.

The kettle contains 1.5 kg of water.

The kettle is switched on.

Calculate the energy needed to raise the temperature of the water by 50 °C.

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

Use the equation

Δ Q = m × c × Δ θ

The amount of energy, E, needed to bring the water to boiling point is 670 000 J.

The kettle has a power of 3500 W.

Calculate the time, t, it takes to bring the water to boiling point.

Use the equation

A student measures the density of glass.

The student has

− a bag of marbles, all made from the same type of glass

− a weighing balance

− a plastic measuring cylinder containing water

Describe how the student could find, as accurately as possible, the density of the glass used for the marbles.

A beaker contains 0.25 kg of water at room temperature. The beaker of water is heated until the water reaches boiling point (100 °C). The specific heat capacity of water is 4200 J/kg °C. The total amount of thermal energy supplied to the water is 84 000 J.

Calculate the temperature of the water before it was heated.

Use an equation selected from the list of equations at the end of this paper.

The heating continues until 0.15 kg of the water has turned into steam. The thermal energy needed to turn the boiling water into steam is 0.34 MJ.

Calculate the specific latent heat of vapourisation of water. Use an equation selected from the list of equations at the end of this paper.

The graph in Figure 13 shows how the volume of 1 kg of water changes with temperature.

Describe how the density of water changes with temperature over the range of temperature shown in Figure 13.

Calculations are not required.

A student uses the apparatus in Figure 3 to determine the specific heat capacity of water.

State the measurements needed to calculate the specific heat capacity of water.

State two ways that the apparatus could be adapted to improve the procedure.

The student decides to measure the temperature of the water every minute while it is being heated.

Figure 4 shows a graph of the student’s results.

Predict the temperature of the water if the heating continues up to 8 minutes.

Another student decides to melt some ice.

The student melts 380 g of ice at 0 °C.

The specific latent heat of fusion of ice is 3.34 × 10⁵J/kg.

Calculate the thermal energy needed to melt the ice.

Select an equation from the list of equations at the end of this paper.