We got all the stuff we needed and started the experiment.
This is what we used: A bowl, 50ml of water, eye dropper, food colouring and dishwash detergent.
We predicted that when we added the detergent it would move like the milk did. So we added 50ml of water to the bowl and added 4 drops of food colouring. Then we added the detergent and the food colouring sunk to the bottom! We even tried adding more drops of detergent and it still didn't move! So our conclusion was food colouring doesn't move in water. Our test was fair because we added the right amount of food colouring.