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Use cornstarch to make a substance that behaves like a solid and a liquid

Science Projects - Earth Science and Astronomy

Suitable For

Grade 4

Difficulty

2

Time Required

 <24 Hours

Supervision

Advised

What’s it about?

The large land masses of the earth are slowly but constantly drifting about the earth’s surface. The surface layer of the earth is called the ‘crust’ and just below is a layer called the ‘mantle’.

These layers are both made of solid material, but a small layer in between the crust and the mantle exists called the ‘partial melting zone’. This layer consisting of a strange putty-like liquid, and is the reason the earth’s crust ‘slides’ around on top of the mantle layer. In this science experiment we will create is similar putty-like liquid that behaves both like a solid and a liquid:

Topics covered

Mantle, Partial melting zone, Viscosity

What will I need?

  • BOWL
  • MEASURING CUP
  • CORNSTARCH
  • SPOON
  • TAP WATER
  • PLASTIC CUP

Procedure (Method)

The large land masses of the earth are slowly but constantly drifting about the earth’s surface. The surface layer of the earth is called the ‘crust’ and just below is a layer called the ‘mantle’. These layers are both made of solid material, but a small layer in between the crust and the mantle exists called the ‘partial melting zone’. This layer consisting of a strange putty-like liquid, and is the reason the earth’s crust ‘slides’ around on top of the mantle layer. In this science experiment we will create is similar putty-like liquid that behaves both like a solid and a liquid:

  1. Pour ½ a cup (125ml) of water into a bowl and while stirring constantly, add 1 tablespoon of corn starch to the water until is ‘dissolves’.
  2. Gradually add another full cup (250ml) of corn starch to this mixture one table spoon at a time, stirring vigorously after each spoon addition to avoid lumping. The mixture will become very hard to stir.
  3. Pour the mixture into a plastic cup and notice how it behaves when flowing.
  4. Your ‘silly’ putty is now ready for use! Pick it up and play with it and notice how it starts to melt in your hands when holding it still and how it becomes very hard when you compress it!

How does it work?

‘Viscosity’ is the term used to describe the ability of a liquid to flow, in other words, the level of internal friction within a liquid affecting its rate of flow. In the earth’s ‘partial melting zone’, the high pressures that exist turn the rock into a partially liquefied substance of high viscosity. You can say it’s a kind of putty-like liquid sea, upon which the continents drift!

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