Materials Required:
- Glass jar with lid
- Tap water
- 1 tablespoonful of salt
Procedure:
- Fill up a clear glass jar, such as a mayonnaise jar, with tap water. Set the jar in front of a bright window and watch the water at the top. Air bubbles will rise to the surface.
- After the bubbling has stopped and the water becomes clear, add a tablespoonful of salt to the jar. Screw the lid on the jar and turn the jar over once. Then return it on the upright position. Study the water again. More bubbles will rise. Where did they come from?
This is what happens:
Water contains air, even though you can’t see it. This air is usually dissolved in the water. You saw some of the excess air rising as bubbles in the first part of the experiment. When you added the salt, more air was driven from the water than air, and it replaces the air. Fish in lakes and streams are able to take air directly from water by passing water through their gills.
