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Density of Materials

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Density describes how closely packed the particles are in a solid, liquid or gas.

Solids, liquids and gases

All matter contains particles. The difference between the different states of matter is how the particles are arranged:

in a solid - particles are tightly packed in a regular structure

in a liquid - particles are tightly packed but free to move past each other

in a gas - particles are spread out and move randomly

There is little difference between the density of a liquid and its corresponding solid (eg water and ice). This is because the particles are tightly packed in both states. The same number of particles in a gas spread further apart than in the liquid or solid states. The same mass takes up a bigger volume - this means the gas is less dense.

Density also depends on the material. A piece of iron with the same dimensions as a piece of aluminium will be heavier because the atoms are more closely packed.

Scientists can measure how tightly packed the particles are by measuring the mass of a certain volume of the material, for example, one cubic centimetre.

Material

Density in grams per cubic centimetre (g/cm³)

Iron

7.8

Ice

0.98

Water

1

Air

0.00129

Calculating density

Density can be calculated using the equation:

This is when:

density ( p ) is measured in kilograms per metre cubed (kg/m 3 )

mass ( m ) is measured in kilograms (kg)

volume ( V ) is measured in metres cubed (m 3 )

Example

What is the density of a material if 0.45 cubic metres (m 3 ) of it has a mass of 0.2 kg?

Question

What is the density of a metal if 4 cubic metres (m 3 ) of it has a mass of 2,200 kg?

Reveal answer

The units for density

Although the standard unit for mass is kilograms (kg) and for volume is cubic metres (m 3 ), in many laboratory situations it is the norm to find the mass in grams (g) and volume in cubic centimetres (cm 3 ).

Calculating density using grams and centimetres cubed would give a density unit of grams per centimetre cubed (g/cm 3 ).

Question

What is the density of a material if 15 cm 3 of it has a mass of 30 g?

Reveal answer

1 g/cm 3 is equal to 1,000 kg/m 3

To convert from kg/m 3 to g/cm 3 , divide by 1,000.

To convert from g/cm 3 to kg/m 3 , multiply by 1,000.

Aluminium has a density of 2.7 g/cm 3 , or 2,700 kg/m 3 . Lead has a density of 11.6 g/cm 3 , or 11,600 kg/m 3 .

Iron has a density of 7.9 g/cm 3 . What is this in kg/m 3 ?

7.9 multiplied by 1,000 gives 7,900 kg/m 3 .

Question

What is the density of an object in kg/m 3 if it is 653.1g/cm 3 ?

Reveal answer

653.1 multiplied by 1,000 gives 653,100 kg/m 3 .

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Density - Density of materials - AQA - GCSE Physics (Single Science) Revision - AQA - BBC Bitesize

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1 2 3 Page 1of 3 Density describes how closely packed the particles are in a solid, liquid or gas. All matter contains particles.

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Temperature Change & Energy

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Adding or removing from a material can change its state. Heating a solid material will cause it to from a solid to a liquid. Continued heating will cause the liquid to boil or to form a gas. In some instances, a solid material can go straight to being a gas without first becoming a liquid when heated. This process is called .

Cooling a gas will cause it to from a gas to a liquid and cooling it further will cause it to from a liquid to a solid.

Boiling is an active process. People actively apply energy to a liquid to turn it into a gas using a heater such as a kettle.

on the other hand is a passive process. The liquid slowly absorbs energy from the surrounding area so that some of its particles gain enough energy to escape the liquid.

Throughout all of these changes the number of particles does not change, just their spacing and arrangement. As a result the total mass does not change.

These changes in state are called physical changes because the process can be reversed (eg by cooling instead of heating). This is different to the changes seen in a chemical reaction, which cannot be reversed so easily.

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States of matter - Temperature changes and energy - AQA - GCSE Physics (Single Science) Revision - AQA - BBC Bitesize

# data[].attributes.attachment_link.description
Adding or removing from a material can change its state. Heating a solid material will cause it to from a solid to a liquid. Continued heating will cause the liquid to boil or to form a gas. In some instances, a solid material can go straight to being a gas without first becoming a liquid when heated.

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Particles in Gases

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Particle motion - Particles in gases - AQA - GCSE Physics (Single Science) Revision - AQA - BBC Bitesize

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Learn about and revise particle motion, gas pressure and the relationship between pressure and volume with GCSE Bitesize Physics.

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Sample Exam Questions

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Multiple choice questions are perhaps the easiest to complete - you simply put a cross in a box - however, the questions often have two answers that could, at first glance, be correct. Don't make the mistake of reading the first answer and thinking this is correct without checking all the others.

If it says 'Tick box', you must tick one box. If you leave it blank or tick two or more boxes, you will get zero marks. These multiple choice questions will not start with command words like 'describe' or 'explain'. They will be written in the form of a question like 'What...?' or 'Why...?'.

There will be more multiple choice questions on the Foundation paper.

Sample question 2 - Foundation and Higher

What name is given to the total kinetic energy and potential energy of all the particles of helium gas in the balloon?
This question is AQA material which is reproduced by permission of AQA.

Internal energy is the name given to the total kinetic and potential energy of all particles in a substance. Internal energy is changed by heating or cooling the substance. Changing the internal energy of a substance will cause a change in temperature or state.

Sample question 3 - Higher

This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.

Density is calculated by dividing a mass, measured in kilograms, by a volume, measured in metres cubed.

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Particle model of matter - Multiple choice questions - Sample exam questions - AQA - GCSE Physics (Single Science) Revision - AQA - BBC Bitesize

# data[].attributes.attachment_link.description
Multiple choice questions are perhaps the easiest to complete - you simply put a cross in a box - however, the questions often have two answers that could, at first glance, be correct. Don't make the mistake of reading the first answer and thinking this is correct without checking all the others.

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Density of Materials

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Density - Density of materials - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize

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Learn about and revise density of materials and how to measure the density of various materials with GCSE Bitesize Combined Science.

# data[].attributes.body
Temperature Change & Energy

# data[].attributes.attachment_link.readable_text
Adding or removing from a material can change its state. Heating a solid material will cause it to from a solid to a liquid. Continued heating will cause the liquid to boil or to form a gas. In some instances, a solid material can go straight to being a gas without first becoming a liquid when heated. This process is called .

Cooling a gas will cause it to from a gas to a liquid and cooling it further will cause it to from a liquid to a solid.

Boiling is an active process. People actively apply energy to a liquid to turn it into a gas using a heater such as a kettle.

on the other hand is a passive process. The liquid slowly absorbs energy from the surrounding area so that some of its particles gain enough energy to escape the liquid.

Throughout all of these changes the number of particles does not change, just their spacing and arrangement. As a result the total mass does not change.

These changes in state are called physical changes because the process can be reversed (eg by cooling instead of heating). This is different to the changes seen in a chemical reaction, which cannot be reversed so easily.

# data[].attributes.attachment_link.title
States of matter - Temperature change and energy - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize

# data[].attributes.attachment_link.description
Adding or removing from a material can change its state. Heating a solid material will cause it to from a solid to a liquid. Continued heating will cause the liquid to boil or to form a gas. In some instances, a solid material can go straight to being a gas without first becoming a liquid when heated.

# data[].attributes.body
Particles in Gases

# data[].attributes.attachment_link.title
Particle motion - Particles in gases - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize

# data[].attributes.attachment_link.description
Learn about and revise particle motion, gas pressure and the relationship between pressure and volume with GCSE Bitesize Combined Science.

# data[].attributes.body
Sample Exam Questions

# data[].attributes.attachment_link.readable_text
Multiple choice questions are perhaps the easiest to complete - you simply put a cross in a box - however, the questions often have two answers that could, at first glance, be correct. Don't make the mistake of reading the first answer and thinking this is correct without checking all the others.

If it says 'Tick box', you must tick one box. If you leave it blank or tick two or more boxes, you will get zero marks. These multiple choice questions will not start with command words like 'describe' or 'explain'. They will be written in the form of a question like 'What...?' or 'Why...?'.

There will be more multiple choice questions on the Foundation paper.

Sample question 2 - Foundation and Higher

What name is given to the total kinetic energy and potential energy of all the particles of helium gas in the balloon?
This question is AQA material which is reproduced by permission of AQA.

Internal energy is the name given to the total kinetic and potential energy of all particles in a substance. Internal energy is changed by heating or cooling the substance. Changing the internal energy of a substance will cause a change in temperature or state.

Sample question 3 - Higher

This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.

Density is calculated by dividing a mass, measured in kilograms, by a volume, measured in metres cubed.

# data[].attributes.attachment_link.title
Particle model of matter - Multiple choice questions - Sample exam questions - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize

# data[].attributes.attachment_link.description
Multiple choice questions are perhaps the easiest to complete - you simply put a cross in a box - however, the questions often have two answers that could, at first glance, be correct. Don't make the mistake of reading the first answer and thinking this is correct without checking all the others.