Density

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

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

Figure 3 shows a metal key and some apparatus.

Using the apparatus shown in Figure 3, describe how the student can find the density of the metal key.

A student heats an aluminium block, as shown in Figure 4.

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 3 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 4 shows the values of some properties of the wax.

The wax has a mass of 3.9 kg.

Using information from Figure 4, calculate the volume of the wax when it is all liquid.

Use the equation

volume =_........ ³

State, using information from Figure 4, how the volume of the wax changes when it becomes a solid.

Explain why, using Figure 4, the time from R to S is much shorter than the time from Q to R on the graph in Figure 3.

Figure 13 gives information about the density of aluminium.

Explain the difference between the density of solid aluminium and the density of liquid aluminium in terms of the arrangement of particles.

A student boils some water.

Calculate the amount of thermal energy needed to change 60.0 g of water to steam at its boiling point.

The specific latent heat of vaporisation of water, L, is 2.26 × 10⁶ J/kg.

Use the equation

amount of thermal energy =_........ J

A coil of copper wire has a mass of 14.1 g.

Calculate the volume of the copper wire.

Use the equation

volume =_........ cm³

Figure 4 gives information about the density of aluminium.

Explain the difference between the density of solid aluminium and the density of liquid aluminium in terms of the arrangement of particles.

A student boils some water.

Calculate the amount of thermal energy needed to change 60.0 g of water to steam at its boiling point.

The specific latent heat of vaporisation of water, L, is 2.26 × 10⁶ J/kg.

Use the equation

amount of thermal energy =_........ J

Some students measure the volume of a lump of modelling clay using a measuring jug, as shown in Figure 5.

Using Figure 5, estimate the volume of the modelling clay in cm³.

You may assume that 1 litre = 1000 cm³.

volume =_........ cm³

Which of these means changing state from solid directly to gas?

An object has a mass of 7.22×10^–2kg and a volume of 2.69×10^–5m³.

Calculate the density, ρ, of the object.

Use the equation

State the unit.

density =_........ unit_........

Aluminium has a melting point of 660C.

The absolute zero of temperature is –273C.

Calculate the melting point of aluminium in kelvin.

melting point of aluminium =_........ K

Describe the motion of particles in liquid aluminium (above 660C).

*(d) The table shows some properties of two materials used as thermal insulation.

The higher the R‑value, the better the thermal insulating properties of the material.

Assess which of these materials may be the more suitable to use as thermal insulation in a building.

Your answer should compare the properties of fibreglass and polystyrene given in the table.

Equations

Which of these means changing state from solid directly to gas?

An object has a mass of 7.22×10^–2kg and a volume of 2.69×10^–5m³.

Calculate the density, ρ, of the object.

Use the equation

State the unit.

density =_........ unit_........

Aluminium has a melting point of 660C.

The absolute zero of temperature is –273C.

Calculate the melting point of aluminium in kelvin.

melting point of aluminium =_........ K

Describe the motion of particles in liquid aluminium (above 660C).

A student determines the volume of a piece of metal by measuring the volume of water that it displaces.

The student wrote the following in his notebook.

The student’s description is incomplete.

Suggest two sentences that the student could have included to provide a more complete description of the correct procedure.

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 11 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.

mass =_........ g

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 12 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.

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 3 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.

mass =_........ g

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.

Describe what happens when a substance experiences sublimation.

Describe, in terms of particles, two differences between a solid and a liquid of the same substance.

Figure 13 shows the dimensions of a solid block of concrete.

Density of concrete, ρ, = 2100 kg / m³.

Calculate the mass of the concrete block.

Use the equation:

m = ρ × V

mass of concrete block =_........ kg

Figure 14 shows a shed made mostly of concrete blocks.

State two practical ways to reduce heat loss from this shed.

*(d) A student has two metal strips and a ruler, as shown in Figure 15.

A teacher tells the student that

• one metal strip is made of aluminium

• the other metal strip is made of stainless steel.

The student looks up data in a reference book, finding some density values:

density of aluminium = 2710 kg / m³

density of stainless steel = 7850 kg / m³

The student has access to more of the same metal strips, if needed, and may ask for any extra measuring devices.

Plan how the student could confirm the teacher’s statements, by determining the density of each of the strips as accurately as possible.

Describe, in terms of particles, two differences between a solid and a liquid of the same substance.

Figure 3 shows the dimensions of a solid block of concrete.

Density of concrete, ρ, = 2100 kg / m³.

Calculate the mass of the concrete block.

Use the equation

m = ρ × V

mass of concrete block =_........ kg

Figure 4 shows a shed made mostly of concrete blocks.

State two practical ways to reduce heat loss from this shed.

On a very cold day, the temperature of the air is −4 °C.

Calculate the value of this temperature on the kelvin scale.

temperature =_........ K

Figure 9 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.

density of copper =_........ kg/m³

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

Figure 10 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 11.

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

specific heat capacity of copper from these results =_........ J/kgC

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 12.

The coil is connected to a low voltage power supply.

Describe how this coil could be used instead of the Bunsen burner in Figure 10.

Figure 1 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.

density of copper =_........ kg/m³

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

Figure 2 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 3.

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

specific heat capacity of copper from these results =_........ J/kgC

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 5a). The student then adds liquid to the measuring cylinder (Figure 5b).

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

Use the information in Figures 5a and 5b.

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 6 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

energy needed =_........ J

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

time to bring the water to boiling point =_........ s

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.

temperature before heating =_........ °C

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.

specific latent heat =_........ MJ/kg

The graph in Figure 6 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 6.

Calculations are not required.

A student uses the apparatus in Figure 8 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 9 shows a graph of the student’s results.

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

temperature of the water =_........ °C

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.

thermal energy needed =_........ J

The volume of 380 g of ice is 410 cm³.

Calculate the density of the ice in g/cm³.

density =_........ g/cm³