Water

65% of the human body is composed of water
70% of the Earth is the ocean
- 98% of water on Earth is in oceans (saltwater) whereas 2% is freshwater, most often found in lakes

water is a polar molecule, meaning that it has both positive and negative charges
- non-polar molecules cannot bond with other molecules of their kind as they only have one charge; bonds must be formed with different charges
- can form non-hydrogen bonds
water can bond with up to four other water molecules
- each individual hydrogen bond is relatively weal, but collectively, the structure is strong
water bonds with other molecules through hydrogen bonds

cohesion—allows water to defy gravity and scale trunks/stems of plants
versatile solvent—polar-opposite molecules form bonds (easy to break apart), beneficial for digestion
less dense—water has low density and will often float when combined with other substances
high specific heat—lots of energy necessary to break water’s hydrogen bonds (hard for temperature to change)
1. specific heat: the amount of heat absorbed or lost due to a change in temperature
2. high specific heat stabilizes ocean temperatures
3. water absorbs and stores heat from the sun during the day while barely warming, and gradually cools during the night and colder months, warming the air above it
evaporative cooling—the hottest molecules have more kinetic energy and are the first to evaporate, leaving the cooler ones behind
1. the fastest (hottest) molecules evaporate
2. helps protect terrestrial organisms from overheating and contributes to the stability of temperatures in lakes and ponds
  1. people are not cooled by sweat itself—we’re cooled by the evaporation that follows