Properties of Water

Chemical formula for water

H2O

Polarity of Water

has polar covalent bonds; H is partially positive, O is partially negative

Polar Covalent Bond

A covalent bond in which electrons are not shared equally

Hydrogen Bond

Intermolecular bond in which there is an attraction between a slightly positive hydrogen atom and a slightly negative atom on another molecule

Four

Number of bonds one water molecule can form with others

Electronegativity

A measure of the ability of an atom in a chemical compound to attract electrons

Cohesion

Attraction between molecules of the same substance

Adhesion

An attraction between molecules of different substances

Surface Tension

Caused by hydrogen bonding; a measure of the film that forms on the surface of a body of water

Capillary Action

Combination of adhesion and cohesion; allows water to move up a vessel; driven by evaporation

Less Dense as a solid

Water molecules expand as water gets cooler than 4 Celsius. At 0, they lock into place. Ice floats!

4 degrees Celsius

Temperature at which water is most dense

Universal solvent

All the chemical reactions that take place in organisms take place in water

High heat capacity

Water has the ability to absorb a lot of heat without having the temperature rise too quickly

Specific heat of water

4.184 joules

One calorie

Equal to the specific heat of water; 4.184 joules

Kilocalorie

The "calories" found on food labels - food calories are equal to 1,000 scientific calories

Phase changes

Water is the only substance on earth found naturally in all three states: solid, liquid and gas

70%

The amount of the earth's surface that is covered in water; also the relative amount of water found in each of our cells

pH

-log

Solution

A homogeneous mixture of two or more substances

Solvent

A liquid substance capable of dissolving other substances

Solutes

substance dissolved in a solution

Acid

any compound that forms H+ ions in solution

Base

A substance that decreases the hydrogen ion concentration in a solution.

Buffer

compound that prevents sharp, sudden changes in pH

Between 6 - 8

pH of most body fluids

Proton hopping

Hydrogen ions rapidly transfer from one molecule to the next in a vessel of water

Alkaline or basic

Referring to substances with a greater concentration of OH- ions

Hydrophilic

Having an affinity for water.

Hydrophobic

Having an aversion to water; tending to coalesce and form droplets in water.

Evaporative cooling

As a liquid evaporates, its remaining surface cools; sweat demonstrates this

Specific heat of a substance

the amount of energy required to raise 1 g of that substance by 1ºC

Dissociation of water

Breaking apart of the water molecule into two ions of opposite charge; happens spontaneously ~once every 550 million molecules