Wintry Science

Wintry Science

Here’s a seasonally related temperature experiment exploring what happens when we freeze oil & water

You will need:

a clear plastic container,

water,

cooking oil

food colouring (optional),

use of a freezer.

Instructions

1. Pour some water into the clear plastic container. You can add some blue or green food colouring to the water if you like, to help distinguish the water from the cooking oil

2. Add some cooking oil and leave this for a few minutes. After a few minutes the oil will have risen to the top of the container.

So far so good: in fact you may have predicted this would happen as oil is less dense than water.

Interesting in itself as a science fact but this experiment has a twist. Read on! Put the container into the freezer for a few hours.

Remove from the freezer.

It will now be seen that the oil is underneath the water.

What’s Happening?

Water becomes a solid when it freezes but ice floats because it is about 9% less dense than liquid water. In other words, ice takes up about 9% more space than water, so a litre of ice weighs less than a litre of water. The heavier water displaces the lighter ice, so ice floats to the top. In this experiment the water expands when it freezes and (interestingly), unlike most other solids becomes less dense than its liquid form. It also becomes less dense than the oil. This causes the water to rise to the top. Simple really, but very scientific! One consequence of this effect is that lakes and rivers freeze from top to bottom, allowing fish to survive even when the surface of a lake has frozen over. If ice sank, the water would be displaced to the top and exposed to the colder temperature, forcing rivers and lakes to fill with ice and freeze solid.

Have Fun!

Thanks to www.kids-science-experiments and chemistryabout.com