Role of Water in Human Life
About 70% of the earth's surface is covered with water.
Ninety-seven percent of the water on the earth is salt water. Salt Water
is filled with salt and other minerals, and humans cannot drink this water. Although the salt can be removed, it is a difficult and expensive process.
Two percent of the water on earth is Glacier Ice
at the North and South Poles. This ice is fresh water and could be melted; however, it is too far away from where people live to be usable.
Less than 1% of all the water on earth is Fresh Water
that we can actually use. We use this small amount of water for drinking, transportation, heating and cooling, industry, and many other purposes.
Water can take from three forms:
Pure water is Tasteless, Odourless, and Colourless. Water can occur in three states: Solid
, or Gas
Solid water :
ice is frozen water. When water freezes, its molecules move farther apart, making ice less dense than water. This means that ice will be lighter than the same volume of water, and so ice will float in water. Water freezes at 00
Liquid water :
Liquid water is wet and fluid. This is the form of water with which we are most familiar. We use liquid water in many ways, including washing and drinking.
Water as a gas vapour is always present in the air around us. You cannot see it. When you boil water, the water changes from a liquid to a gas or water vapour. As some of the water vapour cools, we see it as a small cloud called steam. This cloud of steam is a inversion of the clouds we see in the sky. At sea level, steam is formed at 1000
The water vapour attaches to small bits of dust in the air. It forms raindrops in warm temperatures. In cold temperatures, it freezes and forms snow or hail.
Presents Of Water On Earth :
The amount of water we have on earth is always the same. However, clean water, is getting rarer because of pollution.
Most of the world's water, about 97% is in the oceans. 1.4 billion Cubic kilometres is saltwater. Only 3% is the freshwater in lakes, rivers and glaciers.
Much of the world has enough fresh water but there are regions that are too dry and don't get enough rain. Developing countries often do not have enough water for their growing populations. Other areas do not have enough water because people waste it.