Convection: Currents you can see

Drifting in a hot air balloon is an amazing way to experience firsthand the phenomenon of convection. But when it comes to visualizing convection, water is often a simpler medium than air.

One easy at-home experiment involves nothing more complex than an ice cube tray, some food coloring, and a large glass or jar. First, color some water – the darker and denser the food coloring in the water, the better the results – and freeze it into ice cubes. When the cubes are ready, fill a large jar or glass with warm water. Ask children what they think is likely to happen when an ice cube goes into it.

When you’re ready, place a cube in the glass and record what happens. Encourage the kids to look closely at the ice cube: The small tendrils of dyed water can be subtle as they snake downward. Ask them to speculate about what might be happening before explaining that the colder and denser water from the ice cube heads to the bottom before rising to mix with the warm water.

If this seems too simple, play with it a bit. Try some different colors or larger ice cubes. You can also reverse the experiment by dyeing the warm water: Heat water almost to boiling, color it with food coloring, and place it in a small jar. Cover the jar with plastic wrap, and seal it with a rubber band. Place the jar with warm dyed water into a larger glass with cold water, and slash the plastic wrap. Watch as the hot, less-dense molecules rise up before they cool and move back down.

These experiments are a fun way to visualize a phenomenon that plays a major part in our climate patterns. Ask your kids how it might play out on a larger scale. If they’ve ever been swimming off the East Coast of the United States, they’ve probably experienced the Gulf Stream. And a basic, everyday weather pattern is a result of convection: wind.