How Do Fish Float?
A simple experiment for children to observe a floating bottle and the effect of adding water to the bottle. Then you can relate this to how a fish floats.
What you will need:
- Sink or tub of water
- Water
- Plastic soda bottle with the top
What to do:
Fill up sink with water. Fill up bottle half way with water and screw on top.
Have each child predict what will happen when the bottle is placed in water. Then, place in water and observe.
Repeat, but fill bottle 3/4 with water.
Were the two outcomes different and why?
After discussing, explain how this information relates to fish (see below.)
How to explain why fish can float or swim in water:
Buoyancy is a force that causes objects to float in a liquid or to rise in gas or air. With no water or less water in the bottle, the greater amount of air pressure and so the bottle is MORE buoyant. It floats. Fish can control their buoyancy in almost the same way. If they allow more air in their swim bladder they will be more buoyant, just like the bottle!
