Water


 * __ What is water? __**



Clickview: Learning About Water

Chemical composition of water


 * __ The Water Cycle __**


 * condensa**tion**
 * precipita**tion**
 * evapora**tion**
 * transpira**tion**
 * accumula**tion**


 * __ Properties of water __**

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Clickview: Experiments with water

// Water is attracted to other water… **Cohesion** // // Water is attracted to other materials… **Adhesion** //



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 * __ Buoyancy __**

Why does a boat float?

When an object is placed in water, there are two primary **forces** acting on it. The force of gravity yields a downward force and a buoyancy force yields an upward force. The **gravitational force** is determined by the object's weight, and the **buoyancy force** is determined by the weight of the water displaced by the object when it is placed in water. If the gravitational force is less than the buoyancy force then the object floats (a boat), otherwise it sinks (a rock). That is, if an object weighs less than the amount of water it displaces then it floats otherwise it sinks.

A boat floats because of **buoyancy** & **displacement**.

**Archimedes principle:** an object placed in liquid is pushed upwards by a weight equal to the amount of water the object displaces.

// **Hmmm.... some people say that the above clip is wrong!!!! Check out the USS Johnny Depth...** //

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So.... why do boats float?

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