In this video, the combination of cornstarch and water results in a substance that exhibits the properties of a solid and a liquid depending on the amount of pressure applied to it. These types of fluids that don’t behave like what we think of as “normal” fluids are called non-Newtonian fluids.
Methodology
Materials
- Corn-starch/ Corn flour
- Water Food colouring
- Mixing bowl and spoon
- Two containers of equal size to measure 2 parts cornflour and 1 part water
Method
- Measure out two parts corn flour and one part water.
- Add food colouring to the water.
- Mix the food colouring and corn flour together in the mixing bowl using a spoon or your hands.
- If the mixture does not appear to be coming together add a small amount of corn flour slowly until the correct constituency is observed.
Precautions
- Food colouring can stain cloths, it is advised that students have aprons and plastic gloves.
- Students have to be warned not to ingest any materials in this experiment.
Teacher Note
The quicksand is made up of tiny, solid particles of cornstarch suspended in water. This type of mixture is called a colloid. When you bang on it with a spoon or quickly squeeze a handful, it freezes in place, acting like a solid. The harder you push, the more compressed and less fluid the parts of quicksand become, but when you open your hand, the quicksand drips like a liquid. Try to stir the quicksand quickly with a finger, and it will resist your movement. Stir it slowly, and it will flow around your finger easily. This is what’s known as a non-Newtonian fluid. It acts more Ooze–it gets more viscous when you apply a shearing force. This is why you should move slowly in a pool of quicksand. The slower you move, the less the quicksand will resist your movement.
Extension Activities and Worksheets
Access to worksheets and extension activities are available in the teacher resource pack to Kitchen Chemistry.
Kitchen Chemistry – Teacher Resource Pack
