Floating Bubbles

This time we are going to produce some floating bubbles. Instead of filling the bubbles with hydrogen or helium, our bubbles will be filled with ordinary air, and will be floating on a layer of a heavier gas.

To try this, you will need:

  • your sink
  • a large bowl
  • vinegar
  • baking soda
  • bubble solution and a bubble wand

We will start by filling the bowl with a heavy gas, carbon dioxide. You have probably heard a lot about it if you pay attention to the news on global warming. It is produced when things burn, when animals breath, and by many chemical reactions, especially between acids and bases. We are going to make some with common, kitchen chemicals.

Place a large bowl in your sink. I tried a two-quart casserole dish, and it worked quite well. Pour about a cup of vinegar into the bowl. Get your bubble solution ready, and blow a few practice bubbles, to be sure that it works well.

Next, be sure that the air in the room is very still. Turn off the air conditioning, heating, ceiling fan, and anything else that makes the air move around. Wait a few minutes to let the air get still. Then sprinkle about 1/3 of a cup of baking soda into the vinegar. It should foam up, producing lots of its own bubbles.

Moving slowly, use your bubble solution to blow some bubbles. You want them to fall into the bowl with the vinegar and baking soda, but be careful not to blow into the sink, since that would blow away the gases in the bowl. As the bubbles reach the top of the bowl, something strange should happen. They float above the liquid without touching it.

When the vinegar reacts with the baking soda, it releases quite a bit of carbon dioxide gas. Carbon dioxide is denser than the air around you, so it stays in the bowl until it is full, and then flows over the edge into the sink. The carbon dioxide is also denser than the air inside the bubbles, so the bubbles float in the bowl, just as a helium balloon floats in the air around us.

Carbon dioxide has many uses, from fire extinguishers to dry ice. It also provides the carbonation in soda, but if you try floating the bubbles with a glass of soda, remember not to drink it afterwards.