Water and its functions
Water and its functions
WATER
Definition:
Water is a universal solvent made up of two elements in the ratio 2:1. The formula of water is H2O.
A universal solvent is a liquid substance like water that helps to dissolve other substances.
Water exists in 3 forms; solid (ice), liquid and gas (vapour).
Sources of water: Water comes from rain, the well, springs, lakes, oceans, rivers streams, ponds, seas etc.
Properties of water
- Water is unique in that it is the only substance that is found in three physical states at same time.
- Water freezes at 0°C and boils at 100°C.
- Water is a universal solvent. Pure water has a pH of 7 (neutral).
- Pure water does not conduct electricity.
- Water has a high specific heat capacity (absorbs a lot of heat before getting hotter).
- Water is highly cohesive. It sticks to itself.
- Water has a very high surface tension.
Importance of water to living things
- Water as a Solvent
Water attracts both positive and negative ions, because of the nature of the chemical bonds in water. Thus, positive ions are attracted to the oxygen in water, while negative ions are attracted to the hydrogen. This allows water to dissolve compounds important for survival, such as glucose gleaned from ingesting food. However, compounds such as oils and fats that are non-polar do not dissolve in water.
- Water as a Temperature Buffer
Water has a high specific heat capacity, meaning it takes a lot of heat to raise its temperature. Thus, water absorbs much heat without the temperature of the organism being raised. This prevents enzymes from becoming overheated and failing to function.
- Water as a Metabolite
The sum total of chemical reactions within an organism is called metabolism. Water is a metabolite, or a chemical involved in reactions. In this way, it is necessary for the continued survival of both plants and animals.
- Water as Living Environment
Water-based organisms such as fish require water to breathe and breed, directly breathing the oxygen dissolved in water. Without a water supply, they could not access oxygen and would suffocate and would not be able to reproduce.
- Water as an insulator
Water also helps insulate the living environment for these organisms. When the body of water is deep enough, the water keeps fish warm during the winter months, even when ice forms on the surface of the water.
Other Functions of Water
- Water aids in seed germination.
- Water helps in gaseous exchange to dissolve respiratory gases.
- Water helps in nutrient transport in plants.
- Water helps in the transport of gametes.
- Water forms part of the protoplasm.
- Water is used by man for personal hygiene.
- Water is used by man for recreation.
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