[IR] Solid or Liquid

This is an experiment Daryl and I did quite sometime ago, it is about non-newtonian fluids.

Things needed for the experiment.
1. A basin
2. Some water
3. A mixing spoon
4. Corn flour
5. Scissors
6. Measuring cup

Steps
1. Measure about 400 ml of water and pour it into the basin.
2. Open the packet of flour using the scissors.
3. Measure about 400g of corn flour with the measuring cup.
4. Pour the 400g of corn flour into the basin of water.
5. Mix flour with water using your hands.
6. Knead the mixture till it is settled.
7. It should look like melted cheese. Yum... : p
See the resemblance???

Now for the Fun Part!!!

Hit the mixture with force.
You should observe...
It feels hard like a solid, but you can clearly see ripples forming from where you hit the mixture but it does not splash out! You should also observe that it seems impossible to penetrate.

Whereas...
If you gently lay your hand on the mixture, your hand should sink through the mixture. And the mixture would gently flow and fill the spaces in the basin!

Try to...
"Tear" the mixture, you should find that you are able to somewhat "pull" and "rip" the mixture apart like a solid but it gently flows back like a liquid!

"Squeeze" the mixture, you should find that instead of flowing out like a liquid, it suddenly becomes hard and you can feel its shape, like a solid. It should feel like plasticine.

To the molecular level...
The 'Super Starch' is just a liquid with corn flour floating in it, but when you hit it with force, the water molecules are forced into the middle of each grain of flour and it becomes a solid!

In everyday life...
If you run over the wet sand, you should find that it is firm, but, if you stroll along, your feet will sink into the sand.

Why does this mixture have such an interesting property?
Some fluids (liquids & gases) mixtures have two forms.
A liquid can become a solid. This is called "isotropy"

The opposite of isotropy is "thixotropy".
Thixotropy is a liquid mixture becoming "more liquid" (more runny).
An example of thixotropy is when you need to get ketchup out of the bottle, so you had hit the base of the bottle. The act of hitting it at the base makes the ketchup "more liquid" so it can flow out easier.

This is a prezi we also created:

http://www.youtube.com/watch?v=_03fAC0pZ0Q