Objective: Students will predict and observe the effects that freezing and thawing have on water as it floats and sinks in oil.
Key Concept: Water floats or sinks in oil depending on its state of matter.
Supplies
Needed:
•
Crayola markers
•
water
• freezer and ice cube tray
• cooking oil
• clear glass or plastic cup
Procedure
and Results:
1.
Create concentrated color by setting a marker into a cup of water for
a few minutes. Pour that colored water into an ice cube tray. Freeze until
solid.
2.
Ask students whether they think water is heavier or lighter than oil.
Ask them to predict whether water will float to the top or sink to the
bottom of a cup of oil. What will happen to water that is frozen solid
versus thawed into a liquid? Ask the children to illustrate their predictions.
3.
Nearly fill a clear cup with cooking oil. Place the colored ice cube into
the cup. It will float to the surface. Ask students who predicted that
to show their drawings.
4.
Watch what happens as the ice cube melts. Observe the colored water sink
to the bottom of the cup. Ask students who predicted that to show their
drawings.
5.
Discuss observations and what caused this to happen. When water freezes
its molecules expand into rigid ice crystals that take up more space than
when they were in a more compact form of matter (liquid). When they are
less dense, they float above the heavier oil. As they melt and the molecules
become more dense, they are heavier than the oil and sink.
