Ever heard the term “heat rises?” First off, there are materials called “fluids,” and these are liquids or gasses (things that can flow). These fluids can move around by many different means, but there is a special process called convection. In convection, materials become less dense with a change in heat and then they can shift around. You might see this process when a hot air balloon rises. On with the experimenting!
- A tall and wide clear glass or clear plastic container, a small jar (get a jar with a small neck if you can), string/thin wire, water, food coloring
- You might get wet with this experiment: do it in the sink or with towels around!
- Tie a length of string or wire around the neck of the small jar
- Fill the tall plastic/glass container with cold water (leave a couple of inches at the top since you’re going to put something inside
- Fill the small jar with hot water and a drop or two of food coloring (watch how the food coloring moves…). I put the water in the microwave for a minute to heat it up
- Using the string attached to the small jar, lower it to the bottom of the big plastic container
- Watch the interaction of the cold and hot water at eye level
Did you see the water “erupting” out of the top of the small jar? I sure hope you did, that was cool. The hot water has a lower density than the cold water and will float, just like when hot air fills up a hot air balloon and floats up. Did you also notice what happened right after all the colored water floated into the big plastic container? Instead of mixing quickly with the rest of the water it stayed separate from the rest. If you wait long enough, the temperature will balance out and then the colors will mix.
What are some other things you can experiment with? Throw some rice into a pot of boiling water (with parent permission of course). Watch the rice. Does it stay still? Do a little research on deep sea vents, see how convection plays a role there. Also look up convection currents, you’ll find things from atmospheric movement, oceans, and even in the crust of the Earth!
Steve Davala is a high school chemistry and physics teacher who likes to write and work with Photoshop. He’s got two kids of his own and subjects them to these science activities as guinea pigs. Follow him on Twitter or email him at firstname.lastname@example.org.