YouTube's best convection currents video! Science demonstration for your students

"Take a deep breath, (Music starts) get ready for one of the most hypnotic things you'll ever see in a science class. Have you heard that heat rises? Well, here you can see it's true for yourself. I've got some food coloring on the bottom of a plastic container, and there's a hot mug right underneath the red food coloring. As it's heated, the water rises.

But I want you to look closely and notice something else. The blue on the sides is being drawn in. You can see it better when I speed it up. Here's the thing I want you to remember: when water moves FROM one place, it doesn't leave a void behind, water from somewhere else has to move in to take its place.

That's why you can see the blue food coloring coming in from the sides. You can see it better from above. Watch that blue food coloring get drawn in. Do you see it? The hot water reaches the top and then it gets pushed to the edges by more hot water rising underneath it.

As it goes out to the edges it starts to get cool, and cool water sinks just as hot water rises, and if you watch really carefully you can see it sink, and get drawn back toward the middle. These are called convection currents, and you see them moving here in two big ovals. They're one of the major things that drive ocean currents. Especially in the deep oceans, but it's not hot water rising that drives the ocean currents, it's really cold water sinking up near the poles.

Here's a piece of ice that I froze with some blue food coloring in it so you can see how cold water sinks. As water sinks at the North Pole, for example water has to flow up from the southern regions to take it's place, and these currents travel around the globe, some of them taking a thousand years to complete their course. Understanding convection currents will help you get a grip on weather systems, and the movements of earth's continents over the eons, and even the workings of a lava lamp. If you want to try this for yourself, click on this link for the directions you'll need Thanks for watching.

(Music fades out).

Labels: CURRENT

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