Density Science Experiment

If you’ve ever had a pillow fight, you’ll know just how much fun they are! This is because pillows are usually filled with fluffy stuffing, which means they have a low density…. so, they don’t hurt much when you get hit with one.

However, you’d never have a brick fight! This is because bricks have a high density, which means that those hit with them could get seriously hurt.

In this experiment, we will learn about density and observe the density of different objects.

What is Density?

Density is the amount of mass something has per unit of volume.

A denser object will be heavier than a less dense object even if they are the same size, because it essentially has more packed into it – it’s denser.

For example, a block of concrete is heavier than a block of polystyrene of the same size. This is because the block of concrete has a higher density, it has more mass in the same volume which is due to the atomic structure of the object.

Experiment with Density

Density isn’t restricted to objects, liquids have a density too and this experiment uses three liquids of varying densities. In the experiment, you will make predictions about the density of liquids and objects and put it to the test!

What you need:

2/3 cup or 150ml Syrup
(get the cheapest you can, taste doesn’t matter for experiments)
2/3 cup or 150ml Vegetable Oil
2/3 cup or 150ml Water
Small objects of varying densities
(e.g. a 10 cent coin, small ball of paper, lego piece or raisin)
Clear glass or jar
Paper and pencils
Food colouring (optional)

Note: You could also just use just 1/3 cup for each of the above fluids, which is often not much more than 1 cup in size, and will also cost less.
We wanted this much so it would look even more impressive for photos. It’s up to you.

Prepare the Liquids

These three liquids have different densities.
Can you try and guess what order they would go in from least dense to most dense?
Pour your water into the jar or glass followed by the oil and then syrup
Watch as each layer settles. Was your prediction right?

Predict, Test and Conclude

Collect together at least five different objects that you think may have varying densities. Like a coin, a small toy, a small piece of paper, a paper clip, a piece of lego, a raisin or a nut.
Write down your predictions about where each object will sit in the jar.
One by one put the objects in the jar and write down your observations about how they sink or float.
Write your conclusions by listing your objects from least to most dense, remembering the densest will be the heaviest and will sink to the bottom.
Try the experiment again with new objects or liquids...