Have you ever turned a liquid into a solid just by tapping on it? In this science
experiment you make just such a liquid. Can
liquids be lumpy? Can solids be squishy?

Materials:
- Mixing Bowl
- Newspaper
- Cornstarch
- Water
- Spoon

Watch The Lumpy Liquids Squishy Solids Video


























Process Lumpy Liquids and Squishy Solids Experiment
1) Lay newspaper flat on a table.

2) Place bowl on the newspaper.

3) Put ¼ cup of dry cornstarch into the bowl.

4) Add 1/8 cup or 2 tablespoons of water to the corn starch and stir gently.

5) Slowly mix more water into your cornstarch solution until the entire mixture is wet.
Keep adding water until the cornstarch acts like a liquid when you stir.

6) Tap on the liquid with your finger. Notice it does not splash. It becomes hard like a
solid.

7) If the mix is too liquid, add more cornstarch. The goal is to make a mixture that feels
like a stiff liquid when you stir it gently, but feels like a solid when tapped with a finger or
spoon.

Now heres the cool part. Scoop up some of the cornstarch mix into the palm of your
hand. Slowly work it into a ball. As long as you maintain  pressure on the ball by rubbing
it in your hands, it stays solid. If you cease rubbing, it turns back into a liquid and runs
through your hand.

The Science Behind Lumpy Liquids and Squishy Solids Experiment
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 cornstarch mixture. The solid
cornstarch acts like a crowd of people. Pressing your finger slowly into the mixture
allows the cornstarch to move out of the way, but tapping the mixture quickly doesn't
allow the solid cornstarch particles to slide past each other and out of the way of your
finger.

The term “
viscosity” describes the resistance of a liquid to flow. Water, which has a low
viscosity, flows easily. Honey, at room temperature, has a higher viscosity and flows
more slowly than water. But if you warm honey up, its viscosity drops, and it flows more
easily. Most fluids behave like water and honey, in that their viscosity depends only on
temperature. We call such fluids “Newtonian,” since their behavior was first described
by Isaac Newton (when he wasn’t discovering the laws of gravity or developing the
calculus). The cornstarch mixture you made is called
“non-Newtonian” since its
viscosity also depends on the force applied to the liquid or how fast an object is moving
through the liquid.

Other examples of non-Newtonian fluids include ketchup,
silly putty, and quicksand.
Quicksand is like the cornstarch mixture: if you struggle to escape quicksand, you apply
pressure to it and it becomes hard, making it more difficult to escape. The
recommended way to escape quicksand is to slowly move toward solid ground; you
might also lie down on it, thus distributing your weight over a wider area and reducing
the
pressure. Ketchup is the opposite: its viscosity decreases under pressure. That’s
why shaking a bottle of ketchup makes it easier to pour.

Disposal: First dilute the cornstarch mixture with plenty of water before pouring it down
the drain. Why? What do think would happen to the semi-solid, semi-liquid form that
you prepared if pressure were applied to it by other water in the drain? Yes – a plugged
drain. Now grab some friends and do the Lumpy Liquids and Squishy Solids
Experiment.
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