Science Ace (Non-Newtonian Fluid)

Hi there everyone! Today, I will be sharing on my science ACE - Non Newtonian Fluids.




Materials used in experiment- corn-starch and water (ratio 1:1)

Steps to make a Non-Newtonian fluid:

1)Mix corn starch and water together in a pot or container
2)Mix evenly till the corn-starch acts like a liquid when you stir it slowly.
3)When you tap on the liquid with your finger, it shouldn't splash, but rather will become hard.

Personally, I added too much water at first and I had to wait for the corn-starch to settle down, before I could pour away the excess liquid. In the end, my mixture was a little too thick, but it would still be considered a Non-Newtonian fluid because it exhibited the properties of one.

Properties of a Non-Newtonian fluid
•A fluid whose flow properties differ in any way from those of Newtonian fluids.
•For example, when you poke your finger into a Non-Newtonian fluid, there would be a finger hole left there. This does not happen in Newtonian fluid.
•Hard when you hit it
•Acts like a liquid when you gently touch it.
Properties of a Newtonian fluid
•A Newtonian fluid is a fluid whose stress versus strain rate curve is linear and passes through the origin
•Think of this example - You have to pull the trigger on a water pistol to get the water to squirt out. To make the water to come out faster, you have to pull the trigger harder. Fluids resist flow. This phenomenon is known as viscosity. Therefore these fluids are called Newtonian fluids.
•Viscosity depends on temperature, pressure etc.

So, why does corn-starch mixture happen like this?

An example - Think of a busy sidewalk. The easiest way to get through a crowd of people is to move slowly and find a path between people. If you just took a running start and headed straight for the crowd of people, you would quickly slam into someone and you wouldn't get very far. This is similar to what happens in the corn-starch mixture. The corn-starch mixture acts like a crowd of people. Pressing your finger slowly into the mixture allows the corn-starch to move out of the way, but tapping the mixture quickly doesn't allow the solid corn-starch particles to slide past each other and out of the way of your finger.

The Newtonian fluid theory developed by Isaac Newton tells us that a fluid when applied pressure on, would not have any effect on the viscosity of it. However, corn-starch mixture and a lot of other fluids also act like this. Therefore, they are known as Non-Newtonian fluid.

This therefore explains what is seen in the video, when I hit the mixture, roll the mixture and try to take a lump of it out.

Other examples of Non-Newtonian fluids

Silly Putty
Ketchup
Chilled Caramel Toppings