Oobleck or ‘cornflour gloop’ is simply a mixture made with roughly 2 parts cornflour to 1 part water. So if you have 1 cup of cornflour try adding about half a cup of water to it. Add the water slowly, so you don’t add too much. It will be very hard to mix so you will need a strong arm or spoon. If the mixture is right, it should act quite strange; as it acts like a solid under force and a liquid when it is not under force.
Like a liquid, it can be poured and takes the shape of its container. It can also be picked up, rolled into a ball and kept like this as long as you continue to manipulate it and apply force.
Things to try (ask your child or children what they notice throughout):
- Pick up some oobleck and make it into a ball in your hands then open your palm and relax and watch what happens.
- Poke or tap the surface of the oobleck.
- Leave something small (like a lego brick) on the surface of the oobleck and watch what happens.
Questions to think about:
- What does it feel like?
- What words could we use to describe it?
- How does oobleck behave differently to water and other liquids?
- What is strange about the oobleck?
- How is it similar to any other solids or liquids you know?
- Why do you think it is like this?
Explanation: Oobleck is actually a Non- Newtonian fluid as, unlike other fluids, it changes its viscosity (how thick it is) when force is applied to it. Newtonian fluids, such as water, do not change viscosity when force is applied. There are other non-Newtonian fluids such as ketchup which becomes less viscous (or less thick) when you shake it. This is why shaking the ketchup bottle does indeed help the sauce flow out.
Taking it further:
- To find out more about where the name oobleck comes from and Non-Newtonian fluids read the recent HfL blog: Science and Dr Seuss.
- What happens when you dive bomb into a swimming pool? Watch a video of monkeys enjoying jumping into water. Would the same thing happen in oobleck?
- Can you walk on water? What about oobleck? Brainiacs tried this with custard which is mostly made from cornflour. John Tickle- attempt to walk on custard
- To share their understanding children could write a letter to someone who has never seen oobleck to describe its unusual properties.
Send photos of you making oobleck and you having fun with it to your class teachers or me, at email@example.com.