W is for Water

Here's seven fascinating facts about water...

1. Water comprises 71% of the Earth's surface, mostly in seas and oceans. Because the oceans reflect blue light, the Earth appears blue from space. 
2. 97% of the water on Earth is salt water, with an average salinity roughly equivalent to 34 grams of salt in 1 kg of seawater.
3. The balance therefore represents fresh water, which is rather unevenly distributed on the Earth. 68.7% of this fresh water is trapped in glaciers, ice caps and permanent snow. Of the liquid surface fresh water, 87% is contained in lakes, 11% in swamps, and only 2% in rivers. Small quantities of water also exist in the atmosphere and in living beings.
4. The human body contains anything between from 55% to 78% water, depending on age, health, weight, and sex. To function properly, the body needs to be hydrated - the NHS tell us that we should drink about 1.2 litres (six to eight glasses) of fluid every day to stop us getting dehydrated.  If the weather is hotter, the body will need more than this. We also get some fluid from the food we eat. 
5. 70 -75% of the human brain is water.
6. Water is unusual in that its solid form, ice, is less dense than its liquid form, which is why ice floats. 
7. Water is often called the "universal solvent" because it dissolves more substances than any other liquid.