# Solve density and mass problems

## Home learning focus

Learn about density and mass and how to solve problems relating to them.

This lesson includes:

- two videos
- a learning summary
- three activities with answers

# Learn

## Density

Density describes how much **space** an object or substance takes up (ie its **volume**) in relation to the amount of **matter** the object or substance has in it (its **mass**).

To work out the density of an object or substance you can use this equation:

density = mass ÷ volume

The more dense a substance is, the heavier it feels for its size. If an object is heavy and compact, it has a high density.

### Density in real-life situations

Watch this short case study video of a camera man explaining why density is an important factor when filming underwater.

## Density values

The units used for density depend on the units used for mass and volume, but are usually: **g/cm³** (if mass is measured in g and volume in cm³).

Here are the densities of some everyday substances:

Steel =

**7.82 g/cm³**Water =

**1.00 g/cm³**Air =

**0.0013 g/cm³**

These values show that the **steel** (solid) is the most dense while the **air** (gas) is the least dense.

## Working out density

We now know that we can work out the density of an object if we know its mass and volume:

density = mass ÷ volume

Click through the slideshow below to see how you can work out the density of a chain by dividing its mass by its volume.

## Density and mass problems

As you have learned, **mass** is the amount of matter that makes up an object or substance. If you know the **density** and **volume** of something, you can work out its mass with this equation:

mass = density × volume

Watch this video from Pearson to learn how to solve problems relating to density and mass, by working out the density of a new metal.

# Practice

## Activity 1

**The density of a brooch**

To get you thinking, have a go at this quick activity from BBC Bitesize, KS3 Maths to work out the density of a brooch when you know its mass and volume.

## Activity 2

**Interactive activity - practise finding density and mass**

Now have a go at the questions in this interactive activity from MyMaths, Oxford University Press where you need to work through various problems to find density and mass. Click the 'Practice' button to enter. You can mark your answers within the activity.

## Activity 3

**Density and mass problems worksheet**

Keep going - look at the problems relating to density and mass in this worksheet from Pearson, Maths Progress which test your skills in more depth. You will need a calculator to complete the questions. Write your answers on a piece of paper.

Click here to see the correct answers to the questions.

# There's more to learn

Have a look at these other resources around the BBC and the web.