Stack different fluids on top of one another and discover why the layers don't mix.
What you will need
a tall clear jar or PET bottle
syrup or honey
water
oil
screws, paperclips, pen lids and any other small colourful objects made of different materials
ice cubes
detergent, salt and hot water (optional)
What to do
Carefully pour the syrup, water and oil into the container, what do you see?
Drop in the small objects. Do they reach the bottom? Try dropping in the ice-cubes.
What's happening?
Density is a measurement of how dense something is - how much of it is there in a given space. If you divide something's mass (how much it weighs) by its volume (how much space it takes up), you can find it's average density.
Syrup, water and oil all have different densities. This means they don't mix – they prefer to form three different layers. The denser fluids sink to the bottom while less dense fluids rise to the top.
We call the column you have just made a Density-o-Meter. You can see how dense objects are by where they sit in the column relative to oil, water and syrup.
Temperature can affect the density of fluids and solids. Generally the colder something is, the denser it is. The bizarre exception is ice, which is lighter than water because ice arranges itself in a crystalline structure that takes up more room than water.
Try adding a few droplets of food colouring to half a cup of very hot water (ask an adult to help you) and add it to your density column. Does the colouring spread out to all the water or does it form another layer?
Try adding very salty water of another colour. Where does it sit?
Try some more Science by Email activities about density:
