Salt Volcano
(Lava Lamp)
Materials:
o
A
glass jar or glass
o
Vegetable
Oil
o
Salt
o
Water
o
Food
Coloring (optional)
Experiment:
1.
Pour
about 3 inches of water into the jar
2.
Pour
about 1/3 cup of vegetable oil into the jar.
When it settles, is the oil on top of the water or underneath?
3.
If
you want, add a couple drops of food coloring to the jar. What happens?
4.
Shake
salt on top of the oil while you count slowly to 5.
5.
Add
more salt to keep the action going for as long as possible.
Explanation:
Why does the oil float on
the water?
Oil
floats on water because a drop of oil is lighter than a drop of water the same
size. Another way of saying this is to
say that water is denser than oil.
Density is a measurement of how much a given volume of something
weighs. Thins that are less dense than
water will float in it. Things that are more dense than water will sink.
Even though oil and water are both liquids, they are
what chemists call immiscible liquids.
That’s a fancy word that means they don’t mix.
What happens when I pour salt on the oil?
Salt is heavier than water, so when you pour salt on
the oil, it sinks to the bottom of the mixture, carrying a blob of oil with
it. In the water, the salt starts to
dissolve. As it dissolves, the salt
releases the oil, which floats back up to the top of the water.
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