Changes of state

Diagram 1 shows the apparatus a student uses to determine the specific heat capacity of a liquid.

Describe a suitable method the student could use to determine the specific heat capacity of the liquid.

The graph shows the student’s results.

What is happening to the liquid between points P and Q on the graph?

Use the graph to determine the change in temperature of the liquid after 15 minutes of heating.

The power of the heater is 48 W and the mass of the liquid is 0.53 kg.

Calculate the specific heat capacity of the liquid.

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

The diagram shows forces used to turn a tap.

State the formula linking moment, force and perpendicular distance from a pivot.

Calculate the total moment of the two forces required to turn the tap around the pivot.

Give your answer in N cm.

total moment =_........ N cm

The tap is used to put some water in a bucket.

Describe the arrangement and motion of the water particles in liquid water.

You may draw a diagram to help your answer.

A sample of liquid gallium is allowed to cool in a laboratory.

The liquid gallium freezes to become a solid.

Complete the diagram by drawing the arrangement of particles in a liquid and the arrangement of particles in a solid.

The first particle in each box has been drawn for you.

The initial temperature of the sample of liquid gallium is 80 °C.

The freezing temperature of gallium is 30 °C.

The final temperature of the solid gallium is 20 °C.

Complete the graph to show how the temperature of the gallium changes during the time that it cools to 20 °C.

Add appropriate values to the temperature axis.

The photograph shows a water bath that a technician uses to heat some water.

The water bath is filled with water at an initial temperature of 15C.

Calculate the initial temperature of the water in kelvin.

The technician heats the water to a final temperature of 60C.

Describe how the energy of the water molecules changes as the temperature of the water increases.

The table shows some information about the heating element in the water bath and the heating process.

Calculate the energy transferred by the heating element in the water bath during the heating process.

Calculate the mass of water being heated.

Assume that all the energy is transferred to the thermal store of the water. [for water, specific heat capacity = 4200 J / kgC]

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Some water evaporates as a gas from the water bath.

Describe the arrangement of particles in a gas.

Describe two differences between evaporation and boiling.

A sample of steam (water in a gas state) is cooled using a very cold freezer.

The steam is cooled from an initial temperature of 150 °C.

Calculate the initial temperature of the steam in kelvin (K).

The temperature-time graph shows how the temperature of the steam changes during the cooling process.

The steam eventually becomes ice (water in a solid state).

The graph shows five stages, A, B, C, D and E, of the cooling process.

State which stages of the cooling process show a change of state.

Describe the differences in the arrangement of particles when the sample is in a gas state (steam) and a solid state (ice).

You may draw a diagram to help your answer.

Explain whether or not the energy in the kinetic store of the particles changes when the sample is changing state.

A solid bar of chocolate is taken from a refrigerator.

The temperature of the chocolate bar is 5 °C.

Describe the arrangement and motion of the particles inside the chocolate bar.

The chocolate is heated at a constant rate until the temperature reaches 45 °C.

The chocolate has a melting point of 32 °C and a boiling point of 55 °C.

Describe the motion of the particles in the chocolate when the chocolate is at a temperature of 45 °C.

Which of these is used to measure the temperature of the chocolate?

Use the axes to sketch a graph of how the temperature of the chocolate changes with time when it is heated from 5 °C to 45 °C.

The photograph shows an ice cube placed on a metal tile.

The solid ice cube melts to become liquid water.

Compare the arrangement of particles in a solid with the arrangement of particles in a liquid.

You may draw a diagram to help your answer.

Describe the difference in the movement of particles in a solid compared with the movement of particles in a liquid.

After the ice cube has melted, the liquid water increases in temperature.

The water has a mass of 16 g and a specific heat capacity of 4200 J/kgC.

Calculate the energy transferred to the liquid water as it increases in temperature from 3C to 21C.

A student heats a sample of water.

The student measures the temperature of the sample of water during heating.

The sample of water has a mass of 0.45 kg.

Calculate the energy required to increase the temperature of the water from 16 °C to 100 °C.

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

The diagram shows the temperature-time graph for the sample of water.

Use the graph to determine the time taken from when the water started to boil to when the water stopped boiling.

time taken =_........ minutes

The heater used to heat the water has a power rating of 2200 W.

Calculate the energy required to boil all of the water.

Give a reason why the liquid water should be stirred during the heating.

When water boils, the liquid water becomes a gas called steam.

Describe the changes in arrangement and motion of the molecules in liquid water and the molecules in steam.

Describe the arrangement and motion of particles in a solid.

You may draw a diagram to help your answer.

A solid changes state by melting at a certain temperature.

For phosphorus, this change of state occurs at 44 °C.

Sketch how the temperature of a sample of phosphorus changes when it is heated at a constant rate from –40 °C to 80 °C.

This question is about solids, liquids and gases.

Melting is the process that occurs when a solid changes into a liquid.

Using ideas about particles, describe the process of melting.

A sealed metal flask contains air at room temperature.

The flask is then heated.

The graph shows how the pressure of the air increases as its temperature increases.

Explain how heating the flask increases the temperature of the air inside the flask.

Explain why the pressure of the air increases as its temperature increases.

Using the graph, determine the pressure of the air when its temperature is 400 K.

The air in the flask is now cooled to a temperature of 230 K.

Calculate the new pressure of the air.

pressure =_........

The diagram shows the temperature‑time graph for a substance which is heated at a constant rate.

Which section of the graph shows when the substance is melting?

Which section of the graph shows when all the substance is a solid?

Draw particles in the box to show the arrangement of particles when the substance is a gas.

Which of these statements best describes the motion of particles in a gas?

Name a piece of apparatus that could be used to measure the temperature of the substance.

Determine the boiling point of this substance.

The substance has a mass of 1.2 kg.

Calculate the energy required to raise the temperature of the substance from 10C to 37C.

[assume specific heat capacity of substance = 840 J/kgC]

This question is about liquid nitrogen.

The diagram shows the arrangement of particles in solid nitrogen.

Draw the arrangement of particles in liquid nitrogen.

Describe the motion of the particles in liquid nitrogen.

A teacher uses this method to find the density of liquid nitrogen.

• measure the mass of a container

• pour liquid nitrogen into the container

• measure the total mass of the container and the liquid nitrogen

• read the volume of the liquid nitrogen from the scale on the side of the container

Give a safety precaution the teacher should take when pouring the liquid nitrogen.

State the name of the apparatus that the teacher should use to measure the mass of the container.

The table shows the teacher’s results.

Calculate the mass of liquid nitrogen in the container.

State the formula linking density, mass and volume.

Calculate the density of the liquid nitrogen.

Give a suitable unit.

Over time, the liquid nitrogen warms up and changes state from a liquid into a gas.

Describe the changes to the arrangement and motion of particles when the liquid nitrogen changes state.

Conventional power stations burn fuel in a furnace.

The fuel can be a solid, a liquid or a gas.

Describe the motion of particles in a solid, a liquid and a gas.

When the fuel is burned, energy is transferred from the fuel to the water.

The water boils and turns into steam.

Describe how energy stored in the fuel is transferred to the water.

Refer to energy stores and transfers in your answer.

The temperature-time graph shows how the temperature of the water changes as it is heated in the furnace at a constant rate.

Explain how the graph shows that the water changes state as it is heated.

A student does an investigation to determine the temperature-time graph for water as it changes state from ice to liquid water.

The diagram shows the student’s apparatus.

The ice has an initial temperature of –17 °C.

After 5 minutes, the ice begins to melt.

After a further 6 minutes, all the ice has melted.

The investigation continues for a total time of 20 minutes.

Sketch a graph on the axes to show how the temperature changes with time.

Assume that the rate of energy transfer from the heater to the ice cubes is constant.

Suggest a precaution the student should take to obtain high quality data.

During the experiment the heater transfers 2500 J of energy to the beaker.

The beaker has a specific heat capacity of 880 J / kg °C and a mass of 48 g.

Calculate the increase in the temperature of the beaker.

This question is about sound waves.

Sound is an example of a type of wave.

State the name of this type of wave.

The speed of sound in liquids is greater than the speed of sound in gases.

Describe the arrangement of particles in liquids and in gases.

You may use diagrams to help your answer.

Suggest why the speed of sound in liquids is greater than the speed of sound in gases.

A buzzer is an electrical device that produces sound.

The frequency of sound produced by the buzzer is 1400 Hz.

State the formula linking speed, frequency and wavelength of a wave.

Sound travels at a speed of 340 m/s in air.

Calculate the wavelength of the sound wave from the buzzer.

Two students use this method to investigate sound from a moving source.

Student A connects a piece of string to the buzzer.

She spins round so that the buzzer moves in a horizontal circular path.

● she spins round at a slow speed

● she then spins round at a high speed

Student B stands several metres away from student A.

The sound heard by student A is different to the sound heard by student B.

Discuss the differences in the sounds heard by student A and student B.

Stearic acid is a solid at room temperature and melts at a temperature of 69 C.

A student investigates the specific heat capacity of solid stearic acid.

He heats a sample of stearic acid from room temperature using an electrical heater and measures its temperature using a data logger and temperature sensor.

The graph shows his results.

The student starts heating the stearic acid at 130 seconds.

Determine the time it takes to heat the stearic acid until it reaches its melting point.

The stearic acid gains 39 kJ of energy during the time it is heated to its melting point.

Calculate the mean (average) power of the heater.

Give a unit with your answer.

[assume no energy lost to surroundings]

The mass of stearic acid used in the investigation is 0.45 kg.

The stearic acid gains 39 kJ of energy when it is heated to its melting point.

Calculate the specific heat capacity of stearic acid.

You should use data from the graph in your calculation.

specific heat capacity =_........ J/kgC

This is a question about a melting ice cube.

The diagram shows an ice cube placed on the ground.

The mass of the ice cube is 3.7 g and its area of contact with the ground is 2.610^–4 m².

Calculate the pressure the ice cube exerts on the ground.

The ice cube melts and becomes a puddle with a larger cross‑sectional area.

Explain how the pressure of the ice cube on the ground changes when it melts.

Ice melts at a temperature of 0C.

On the axes, sketch how the temperature of the ice cube changes as it rises from a temperature of –10C to a temperature of 20C.

Explain the changes that occur when a solid melts.

Refer to particles in your answer.