Save the Ice Cube - Demonstration

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Phriendly Physics Home - Invitation - Background - Demonstration - Exploration

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Materials:

Three cups (plastic or styrofoam). Vegetable oil and water -- both at room temperature (leave out for a while).

Preparation:

Set out three cups: one filled with water, one filled with vegetable oil, and one empty. (Be sure to leave them out so they are room temperature.) Place an ice cube in each one, and explain about heat for a time.

Results:

The ice cube in the water will melt the fastest. The one in oil will melt later, followed by the one in air -- but note that the ice cube in oil will look larger than the one in air (this is a bit deceptive).

Explanation:

Intuitively, you can explain water is denser than oil and much denser than air -- it has more heat. But also important is how contact is being made -- if you look closely at the ice cube in oil as it is melting, you will see water form around the cube and drip off -- separate from the oil. This follows the common understanding "oil and water don't mix" -- the oil does not contact the ice cube as well as water.