With Halloween coming up, what better time to make some of your very own slime?
It’s super easy and quick to make – you just need to mix water and cornflour! Start with a little bit of both, if it seems too runny you can add more cornflour and if it becomes a solid then add more water.
You can also add food colouring and glitter if you want to add some sparkle to your slime.
The slime should become a consistency that appears to be a liquid but if you hit it or try to stir it quickly it becomes a solid – so which is it?
Liquid or Solid?
Slime isn’t actually a solid or a liquid – it is a non-Newtonian fluid, this is a fluid that changes its properties when a stress or force is applied.
The slime we’ve made is a particular non-Newtonian fluid called oobleck (yes it’s a funny sounding word – that’s because it is derived from a Dr. Seuss book). The particles of cornflour don’t dissolve in the water, they become suspended in the water and repel each other. Mechanical stress, such as stirring quickly provides energy that overwhelms the repulsive forces, causing the particles of cornflour to temporarily stick together. When the stress is removed, the repulsion returns and the slime becomes liquidy again.
More Non-Newtonian Fluids
1. Custard behaves just like oobleck, in fact if you filled an entire swimming pool with custard, you would be able to walk across it!
2. Ketchup is almost the opposite of oobleck – it become thinner and runnier under impact, that’s why it helps to bang the end of a ketchup bottle when you’re struggling the get some out.
3. Whipping cream acts differently when under a constant and prolonged stress, such as whipping. If you whip cream for long enough it will appear to go from liquid to solid as it becomes whipped cream.
4. Honey similarly needs prolonged stress to change it’s properties. When you stir honey, it will become more like a liquid than a solid.