So I finally redo an Oo-bleck experiment with students the last school holidays. This time we made sure we have enough corn starch to make it work!
The ingredients for this experiment is really simple and easily prepared:
🔸️2 packs of corn starch
🔸️Food colouring (optional)
Pour in 2 cups of corn starch. Then add in one cup of water. The ratio of starch to water is about 2:1. Keep adding until you get the volume desired.
Drop in some food colouring of your choice. Then mix it with your hand. My students mixed the oobleck together before adding in the food colouring.
Testing out if it gets "hardened" up when he punches the surface.
So one student added blue food colouring while his brother chose pink.
Checking on the consistency of the mixture. We are looking for a texture when we hold some of the mixture in our palms, it hardens and it will flow out when we open up the palms.
Don't be afraid to get dirty when it comes to home experiments! The mess is part of play!
We nailed it! Look at how it looked like a solid when we rolled it within 2 palms and once we released it, it turns back to liquid. Amazing! Sorry I did not manage to capture photos as I was recording a video so I had to screenshot my video instead to get some still shots.
Oo-bleck is a non-Newtonian fluid as it does not abide by the usual Newtonian rule in Physics. However it was also described by Sir Isaac Newton himself in the 1700s. So it is nothing new.
When we grab it like a clump in our pumps, we apply pressure onto it and that is when the starch particles tend to gather together to give a solid "state". The pressure sorts of forces the starch to "toughen" together. It temporarily traps the water molecule together as well. (WHAT A COOL DEFENSE MECHANISM, DON'T YOU THINK SO?)
When we slowly dip our hand into the mixture, it feels just like putting our hand into any bowl of liquid. Same goes when we open our palms and let it go, it flows off our palms like any liquid. This is when no pressure is applied.
In Chemistry, the starch molecules forms a long chain as their molecules are relatively larger. Water molecules flow past the starch molecules like liquid but they get trapped within the starch molecules should there be an external force applied on the area.
My students felt Oo-bleck is like quick sand. I think they are different. I was just thinking if humans can have teamwork like that of how Oo-bleck works. Many times, when external pressure comes, we scattered and want to bail out instead of sticking together. If there is a team sticking together whenever pressure is detected, that will be a very strong and powerful team!
Nevertheless, this was a very fun experiement. Will want to try it at home with my son too. Just REMEMBER, dispose the Oo-bleck in the dustbin instead of flushing it down the toilet or a sink because you never know when it may turn solid and clog our pipes!!!