1. From Molecules to Organisms: Structure & Processes
Properties of Water
Copyright © Rebecca Rehder Wingerden

2. Properties of Water
All life on Earth requires water because it is the medium for biochemical reactions.
water is the main reason the Earth is habitable,
most cells are surrounded by water,
and cells are 70-95% water.

3. Water is a polar molecule.
This polarity creates hydrogen bonds between water molecules.
Water’s chemical structure produces its unique functions.
Ice (solid), ocean (liquid), cloud (vapor):
Water is the only chemical compound on
our planet’s surface that comes naturally
in all three physical states.

4. 1. Water is cohesive and adhesive: hydrogen bonds hold water molecules together (cohesion- attraction between same substances). - Adhesion- attraction between different substances
- Surface tension a measure of how hard it is to break the surface of a liquid (directly related to cohesion).

5. 2. Water has the ability to moderate temperature: due to the hydrogen bonds water can absorb or release a large
amount of heat with only a slight change in its own temperature.
The high specific heat of water minimizes temperature fluctuation to within limits that permit life.
The specific heat of water is 1 cal/g/ºC.
Heat is absorbed when hydrogen bonds break.
Heat is released when hydrogen bonds form.

6. 3. Water expands upon freezing: due to hydrogen bonds
Ice floats in liquid water because the hydrogen bonds are stable between water molecules, making ice less dense.
If ice sank, then many bodies of water would freeze solid when temperatures dropped below freezing.

7. 4. Water is a versatile solvent: due to its polarity
Water molecules dissolve ionic compounds by creating hydration shells.

8. The Potential of Hydrogen (pH) is a measure of the concentration of hydrogen ions in solution (H+).
pH = - log [H3O+].

9. Pure water can dissociate (break apart) into ions.
Ions are atoms, or groups of atoms, with a charge.
Water dissociates into one hydrogen ion (H+) and one hydroxide ion (OH-)
According to the Bronsted-Lowry definition, an acid is defined as any substance which donates a proton (H+) to the solution, increasing the concentration of hydrogen ions. (A base will remove H+ from a solution.)