New draft Experiences and Outcomes within Materials - Chemical Reactions 

Colour changing milk       Activity challenge 

Draft Outcome

I have developed my skills in questioning, observation and recording by taking part in activities, which demonstrate simple chemical reactions safely using everyday ‘kitchen chemicals’   SCN 233Z 

 Chemical Reactions - Colour-changing milk

Milk contains both protein and fat molecules.

Experiment

Pour enough full fat or semi-skimmed milk to cover the bottom of a paper plate and allow settling. Add one drop of 3 or 4 different food colourings close together in the centre of the plate. Dip a cotton bud or a toothpick in the middle being careful not to stir, nothing should really happen. Now dip the cotton bud into some washing up liquid and try again. There should be an explosion of colour! Try placing the cotton bud at different places in the milk.

Milk is made up of water, minerals, vitamins, proteins, and tiny droplets of fat spread throughout the milk. Adding soap does a couple of things to the milk. First, it breaks up the fat globules and weakens the chemical bonds of proteins. This pushes and pulls the food colouring molecules every which way. Colours also explode because milk is mostly water and it has surface tension much like water. Adding soap destroys surface tension by destroying bonds between water molecules. This causes colour to move and then move some more.

Activity Challenge ideas:

Does it work using water?
What kind of milk gives the best results?

Topical Science