Super Science Friday - Marvelous Moving Milk.

This is the first of our hands on experiments focusing on Molecules.  We were so excited we didn't absorb much of the explanation so Mrs Hayman will follow up again next week.

We put milk into a tray.  We added a splash of red food colouring and right next to it a splash of blue.  We touched the surface of the milk with a cotton bud dipped in dish washing liquid.  Some of our predictions were that; the colour would change, it would bubble, it would explode.

We observed what happened and the colours moved around and ended up mixing together.

The science behind it...
Whole milk is a mixture of water, fats, proteins, vitamins, minerals and lactose.  Since milk is made up of mostly water, it shares some of the same properties as water, such as surface tension.
When you put the cotton bud with the detergent into the milk, you break the milk's surface tension, as seen when the colours were pushed away from the centre.  The detergent then starts mixing with the fat in the milk and breaking it down into smaller pieces.
The movement of the colours shows us that the soap is swirling through the solution, distributing the small bits of fat.  Because the skim milk does not have fat, the soap is not slowed down and the colours swirl more quickly.