By Melissa Corkhill
06th March 2009
What you need:
Cornflour
Water
Natural food colouring (optional)
What to do:
Put 2 cups of cornflour in a bowl, add 1 cup of water and 2 tsp of food colouring if using. Mix it up with your hands until all the powder is wet, then continue adding a few drops of water at a time until you have a thick smooth mixture.
This substance can be squeezed, pushed and played with for hours.
Further investigation:
Stir the slime really slowly. This shouldn’t be hard to do.
Now, stir the slime really fast. This should be almost impossible.
Now hit your slime really hard and fast. It should feel like you’re punching a solid.
What’s happening:
Anything that flows is called a fluid. This means that both gases and liquids are fluids. Fluids like water which flow easily are said to have low viscosity, whereas fluids like cold honey which do not flow so easily are said to have a high viscosity.
Cornflour slime is a special type of fluid that doesn’t follow the usual rules of fluid behaviour. When a pressure is applied to slime, its viscosity increases and the cornflour slime becomes thicker. At a certain point, slime actually seems to lose its flow and behave like a solid. Cornflour slime is an example of a sheer-thickening fluid.
Which group do these liquids fit into – high viscosity or low viscosity?
honey, molasses, water, whipped cream, jam, ketchup, milk, yoghurt, juice, tea
Happy investigating
