Changes of state

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.

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.

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.

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 =_........

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.

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.

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 =_........

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 5 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.

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 20 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 =_........

Figure 21 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 22.

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 6 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

Figure 7 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.

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