June 1, 2009

Doing an experiment with a child helps them learn about science. To learn new things, you have to build upon what you already know. In everyday interactions with children, there are many things you can try without lecturing or applying pressures to help them learn science. Of course,  you can’t experiment with a dolphin but here are a few ideas that will help you learn about how dolphins survive in the sea.

1.  How long can you hold your breath? Compare that to how long a dolphin can hold its breath underwater.

2. Do sounds travel underwater? Can you hear sounds when you are swimming? Have you ever played a game where you and a friend make sounds and "talk" underwater,  and try to understand each other?

3. Which freezes more quickly: freshwater or ocean water? Fill two plastic cups halfway, one with freshwater and the other with salty water. Put them in the freezer and check them every ten minutes to see which freezes first. How do the results help to explain why dolphins don’t live in freshwater lakes in places that get very cold in winter?

4. Dolphins dive deep under the water where the water pressure is very great. In the sea,  pressure increases with water depth. Here’s how you can demonstrate that pressure increases with depth. You will need a large, empty tin can, a hammer, a large nail, water, salt, a ruler and a basin or a sink.  Use the hammer and a nail to make three holes, one above the other and each two inches apart in the side of the can. Stand the can on the side of the basin or sink and fill with water. Measure the distance the water spurts out from each of the holes. Try it again with salty water.

a.  Which spurts out further? Why? Remember that the weight of the water is greater over the bottom hole than over the top hole. The heavier the water above, the greater is the water pressure below. At sea level, air pressure is a bit less than 15 pounds per square inch. At 300 feet, the water pressure is about 150 pounds per square inch.

b.  Could humans survive at that pressure without protection? Do research to find out how dolphins survive the pressure of deep waters.

Click on this for Dolphins FAQs 

Posted by: Seymour Simon

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