1. Unit 2: Biochemistry Chapter 2
Properties of Water
Unit 2:
Biochemistry
Chapter 2

2. Water Most important chemical compound in the living world:
70-90% of an organism consists of water
2 Hydrogen (H) and 1 Oxygen (O) connected by covalent bonds
H2O

3. Polar
O is negatively charged, H is positively charged leading to the “magnet-like” behavior of water molecules
Mickey Mouse Molecule
Ears are +
Chin is -

4. Hydrogen Bonds Water molecules attract each other
Very weak hydrostatic attractions, called Hydrogen Bonds (formed between water molecules)

5. Review What does it mean to be a polar molecule?
What are hydrogen bonds (use polarity as part of your answer)?

6. Properties of Water
Cohesion: attraction of water molecules to each other (sticks to itself)
Surface tension: skin-like behavior of water surfaces (water on top of a penny)
High Specific Heat: it takes lots of energy to vaporize water
This acts as a heat buffer for an organism’s body temp!

7. Properties of Water
Adhesion: attraction of H2O to other polar molecules (sticks to other polar molecules)
Capillary action: water binding to polar walls of plant vessels or glass tubes
Great solvent for other polar and charged substances (e.g. salts and sugars)
Expansion when it freezes
Ice floats because it is less dense
Insulation of ponds in winter

8. Review
What are 3 unique properties of water (relate each property to hydrogen bonds)?