Water and the Fitness of the Environment

Why is water important for us?

Water is the substance that makes life possible as we know it on Earth. It is the biological medium here, and possibly on other planets as well.

Furthermore, life on Earth began in water and evolved there for 3 billion years before spreading onto land.

All living beings require water more than any other substance. A human couldn't survive without water more than a week or so.

Which are four emergent properties of water?

- Cohesion

- Moderation of temperature

- Insulation of bodies by floating ice

- The solvent of life

What is a pH scale?

The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 i

s neutral. A pH less than 7 is

acidic. A pH greater than 7 is basic.

Facts:

- 3/4 of Earth's

surface is submerged in water.

- Water is the only common substance to exist in the natural environment in all 3 physical states of matter (solid, liquid, gas).

- The high surface tension of water, resulting from the collective strength of its hydrogen bonds,

allows the water strider (eg.) to walk on the surface of apond.

- Heat passes from the warmer to the cooler object until

the two are the same temperature.

- A compound does not have to be ionic to dissolve in water (eg. sugar).

Summary:

Water is the substance that makes life possible as we know it on Earth. 3/4 of Earth's surface is submerged in water. Some (cohesion, moderation of temperature, insulation of bodies of water by floating ice, the solvent of life) of the emergent properties of water contribute to Earth’s fitness for life.

The concentration of hydrogen is expressed as pH. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. The burning of fossil fuels results in emission of oxides (leading to acid precipition) and increasing amounts of CO₂. Some of the CO₂ becomes dissolved in the oceans, lowering pH and potentially affecting the rate of calcification on coral reefs.

Key words:

polar molecule = molecule whose two ends have opposite charges

cohesion = the binding together of like molecules, often by hydrogen bond

adhesion = the clinging of one substance to another

kinetic energy = energy of motion

heat = form of energy

temperature = a measure of heat intensity (average kinetic energy of the molecules)

vaporization (evaporation) = transformation from liquid to gas

heat of vaporization = the quantity of heat a liquid must absorb for 1 g to be converted from the liquid to the gaseous state

solution = a liquid that is completely homogeneous mixture of two or more substances

solvent = dissolving agent of a solution

solute = substance that is dissolved

acid = a substance that increases the hydrogen ion concentration of a solution

base = a substance that reduces the hydrogen ion concentration of a solution

Extra:

surface tension