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

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 -

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

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

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!

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

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