Water is the basic medium of life. What are the physical and chemical properties of water that make it so unique and necessary for living things?
1. High specific heat
- Water has a high specific heat index. This means that water can absorb a lot of heat before it begins to get hot. The high specific heat index of water also helps regulate the rate at which air changes temperature, which is why the temperature change between seasons is gradual rather than sudden- and why areas near oceans do not experience large temperature changes throughout the year.
2. High Surface Tension
- Water has a very high surface tension. In other words, water is sticky and elastic, and tends to clump together in drops rather than spread out in a thin film. Surface tension is what allows water (and its dissolved substances) to move through the roots of plants and through the tiny blood vessels in our bodies.
3. Universal and powerful solvent
- This allows water to be able to dissolve a large number of different chemical compounds. This feature also enables water to carry solvent nutrients in runoff, infiltration, groundwater flow, and living organisms.
- This property allows plants to extract water from soils by maintaining high solute concentrations in their root cells to generate high osmotic potentials (the force by which an aqueous solution attracts water by osmosis)
4. In a pure state has a neutral pH
- Pure water is neither acidic nor basic. Water changes its pH when substances are dissolved in it.
5. Conducts heat rapidly
- Bodies of water to have relatively evenly distributed temperatures.
6. Is liquid within the range of temperatures most often encountered on earth
- Water molecules exist in liquid form over an important range of temperature from 0 - 100° Celsius. This range allows water molecules to exist as a liquid in most places on our planet.
7. Water molecules are the only substance on Earth that can exist in all three physical states of matter: solid, liquid, and gas
- Incorporated in water's changes of state are massive amounts of heat exchange. This feature plays an important role in the redistribution of heat energy in the Earth's atmosphere.
8. Freezing of water causes mass to occupy a larger volume
- When water freezes it becomes larger and less dense as it becomes solid- so ice floats.
9. Water is denser and provides more buoyancy than air, but is also more viscous and therefore impedes movement
- Because water is denser than air, it provides support for many organisms
- The high viscosity of water hampers movement, so aquatic animals have evolved streamlined shapes to reduce drag encountered in moving through a dense and viscous medium