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1. Why is water carried against the force of gravity up the stem of a plant?
2. Why is less dense when frozen enabling aquatic life to remain alive?
3. Why is water a good lubricant?


1. Water rises up the capillaries in plants mostly due to osmotic pressure (see Biology) although there is a little capillary action. Capillary action is the way in which water can rise up a narrow capillary tube and is due to the attractive forces between water molecules and glass molecules.

2. The fact that ice has a lower density than water means that it will form on the surface of water and so aquatic life can continue in the water beneath the ice. When the ice has formed it also acts as an insulating layer and so the water below it is "more difficult" to freeze.

3. Water is a good lubricant because it is a liquid. However the fact that iron rusts when in contact with air and water makes water not very practicable as a lubricant for iron based materials such as steel.

© Keith Gibbs 2013