Saturday, December 7, 2019
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Let’s Discover: Kinetic Sand

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You can slice it with a knife, shape it like cookie dough or crumble it in your fingers, and not a speck of it will get on your hands or your clothes. What’s the secret of Kinetic Sand?

Manufactured in Sweden, Kinetic Sand looks like regular sand, and in fact, 98 percent of this  novelty product is just that – sand. It’s the other two percent that gives it its strange almost magical properties – an ingredient called polydimethylsiloxane (PMDS) Si(CH3)2-O- we dare you to say that ten times fast! This very common, silicon-based compound also happens to be a key component of Silly Putty – a stretchy, bouncy, rubbery substance every kid loves to play with until it inevitably gets stuck in the carpet.

By adding just a tiny bit of PMDS to some ultra-fine sand, Kinetic Sand becomes what’s known as a non-Newtonian fluid. Unlike Newtonian fluids, which have a constant viscosity that only changes as temperatures or pressures fluctuate (such as water freezing) and take on the shape of the container they’re placed into, non-Newtonian fluids follow their own set of rules. Also known as ‘strange liquids’, non-Newtonian fluids can change their viscosity under stress, such as when you shake them or hit them with a mallet.

As a non-Newtonian fluid, Kinetic Sand acts like a viscous liquid, but also like an elastic solid.  This is because the molecular structure of polydimethylsiloxane is held together by hydrogen bonds, a few of which can be easily broken when small amounts of stress are applied, allowing the sand to flow freely. When more stress is applied – say, when you’re cutting it with a knife – lots of hydrogen bonds are broken apart, allowing the substance to ‘tear’ into very neat pieces.

If you have ever made oobleck with your kids, you have an idea of what is happening here. When you move your fingers slowly through the oobleck it is a running liquid but as soon as you start to move your finger more quickly or hit the surface of the oobleck it behaves like a solid!

In this issue of Let’s Discover, we’ll show you how to create Kinetic sand at home at a fraction of the cost, resulting in hours of fun for your little ones! And the best part is that they can partake in mess-free sand play… indoors! Perfect for those rainy days!sand
Materials:
8 cups of play sand
4 cups of cornstarch
2 cups of water
Large Rubbermaid bin

Procedure:
1. Place 8 cups of play sand into the rubber bin.
2. Add 4 cups of cornstarch to the sand.
3. Mix together the sand and the cornstarch until there are no clumps or visible patches of white. This can be done with your hands, a spoon or a trowel.
4. Add 2 cups of water and incorporate into the sand/cornstarch mixture with your hands.
5. Have fun!

Questions:
1. Describe the texture of the kinetic sand.
2. What happens when you hold the kinetic sand in your right hand and let it slowly pour to your left hand?
3. What happens of you mould the kinetic sand into a sculpture?
4. When you poke the sculpture, what happens?

You can explore more strange materials at the Discovery Centre’s featured Exhibit Strange Matter found in the ExxonMobil Gallery on the third floor. Stop in this March Break and join in daily hands-on activities, solve a mystery, and watch a NEW science show: The Science of Stuff. Check out the Discovery Centre’s March Break schedule of events at thediscoverycentre.ca.