Required practical - Investigating density Revision Notes for AQA GCSE Physics

Required practical - Investigating density

This practical helps you learn how to find the density of different materials. Density tells us how much mass is packed into a certain volume of a substance.

What is the aim?

The aim is to work out the density of both solid objects and liquids by measuring their mass and volume.

What equipment do you need?

You will need these pieces of equipment:

Electronic balance (to measure mass)
Measuring cylinder
Displacement can
Ruler
Various solid objects and liquids to test

Method for solids

Follow these steps to find the density of a solid:

Measure the mass - Use an electronic balance to weigh your solid object. Write down the mass in grammes in your results table.
Find the volume - You can do this in two ways:
- Regular shapes: Measure the length, width and height with a ruler. Then calculate volume using the formula (length × width × height)
- Irregular shapes: Use a displacement can filled with water. When you put the object in, it pushes water out. The volume of water displaced equals the volume of the object

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The displacement method works because the object pushes out exactly the same volume of water as the space it occupies. This is especially useful for objects with complex shapes that would be difficult to measure directly.

Method for liquids

Here's how to find the density of a liquid:

Set up the measuring cylinder - Place it on the electronic balance and set the reading to zero (this is called zeroing)
Add the liquid - Pour your liquid into the measuring cylinder up to a chosen volume mark
Take readings - Record both the mass shown on the balance (in grammes) and the volume shown on the measuring cylinder (in cm³)

Important safety and accuracy tips

chatImportant

Safety first: Only use materials that are safe to handle. Mercury used to be used in these experiments but it's now known to be dangerous.

Avoid parallax error: When reading the volume, make sure your eye is level with the bottom of the curved surface (meniscus). If you read from above or below, you'll get the wrong measurement.

Recording your results

Set up a table like this:

Material	Mass (g)	Volume (cm³)	Density (g/cm³)

Calculating density

Use this formula to work out density:

$\text{density} = \frac{\text{mass}}{\text{volume}}$

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Worked Example: Calculating Density

If an object has a mass of 50g and a volume of 25cm³:

Step 1: Identify the given values

Mass = 50g
Volume = 25cm³

Step 2: Apply the density formula $\text{density} = \frac{\text{mass}}{\text{volume}} = \frac{50\text{g}}{25\text{cm}^3}$

Step 3: Calculate the result $\text{density} = 2\text{g/cm}^3$

Converting between units

Density can be measured in different units:

g/cm³ (grammes per cubic centimetre)
kg/m³ (kilogrammes per cubic metre)

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Unit Conversion Rules:

From g/cm³ to kg/m³: multiply by 1000
From kg/m³ to g/cm³: divide by 1000

Example: Water has a density of 1g/cm³ or 1000kg/m³

What should you conclude?

Your conclusion should explain that you can find the density of any solid or liquid by measuring its mass and volume, then dividing mass by volume. You should also mention that your results can be compared with published values to check accuracy.

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Key Points to Remember:

Density formula: $\text{density} = \frac{\text{mass}}{\text{volume}}$
Two methods: Use displacement for irregular solids, direct measurement for regular solids
Read carefully: Keep your eye level with the meniscus to avoid parallax errors
Units matter: g/cm³ and kg/m³ can be converted by multiplying or dividing by 1000
Safety first: Always use safe materials in your investigation

Required practical - Investigating density (AQA GCSE Physics): Revision Notes