KID STUFF : Mommy, Why Is the Sky Blue?

Picture this: It’s a hot day and you’re cooling off with some iced tea when the kid of the house asks one of those questions parents hate. As a head start, here are two explanations from 3-2-1 Contact magazine to satisfy any child-sized inquiring mind.

* Why does ice float?

When most substances get cold, their molecules vibrate more slowly and move closer together--”contract.” But not water. Its molecules do slow down when the water temperature drops below 39 degrees Fahrenheit, but they move apart, not together.

When water freezes, its molecules arrange themselves in a neat, orderly pattern as they move apart. This pattern takes up more space than unfrozen water molecules. That’s why water expands when it freezes.

The spread-out molecules of ice are not as dense as water molecules, so they float on top of water.

* Do human bodies expand in heat?

Almost any material expands when its temperature rises.

Because it’s about 65% water, your body, it seems, should expand, too. But living things and non-living things deal with temperature changes in different ways.

For example, you sweat to cool off your body and shiver when you need to warm up. Your body is designed to keep your insides humming at 98.6 degrees Fahrenheit.

Your body does change size during the day, though. You’re usually taller in the morning than in the evening because the soft discs in your spine lose liquid after being squeezed all day. Your feet can swell during the day and make your shoes pinch, too.