"Kitchen Slime" Return to list of pracs

Aim: This is very simple to make. Just make sure that the cornflakes are made from corn and not wheat.

Equipment: The equipment includes...  

• newspaper;
• corn flour;
• bowl;
• food colouring (optional);
• water.

Method: Cover the area you will work on, this can be a very messy activity. Put the corn flour in a bowl, about half a cup is a good amount to start with. Add some food colouring now. Add the water slowly and mix with your fingers. Keep adding water until the liquid is a runny cream. Try and tap the slime with your fingers. It should feel hard to tap, but sloppy to pick up or stir. If your mixture is too runny, add more flour, if it is too dry add more water.

Background knowledge: The properties of corn flour are the key in this activity. Most liquids behave like water. Fluids, which flow easily, has a low viscosity (eg water flows easily compared with Golden Syrup which has a high viscosity). Isaac Newton described the behaviour of normal liquids and we call them Newtonian fluids. This slime is what we call a non-Newtonian liquid; other examples are tomato sauce and quick sand. Slime doesn't behave like a normal liquid, it is made up of tiny, solid particles of cornstarch suspended in water, and chemists call this type of mixture a colloid. It is nice and runny when we stir it gently, but quite firm if you hit it hard or try to stir it too fast. Slime behaves like this because when you apply pressure to it, its viscosity increases and the slime becomes harder.