Chemistry Review & Properties of Water Chapter 2 Biochemistry

You must know! The three subatomic particles and their significance The three subatomic particles and their significance The types of bonds, how they form, and their relative strengths The types of bonds, how they form, and their relative strengths The importance of hydrogen bonding to the properties of water. The importance of hydrogen bonding to the properties of water. Four unique properties of water, and how each contributes to life on Earth. Four unique properties of water, and how each contributes to life on Earth.

Chemistry Review Subatomic particles = Protons Protons Neutrons Neutrons Electrons Electrons

Different Chemical Bonds Type:Strength: Ionic bonds (salts)very strong Ionic bonds (salts)very strong Covalent bonds (H 2 O)strong - strength depends on the Covalent bonds (H 2 O)strong - strength depends on the # of e - shared Hydrogen bonds (DNA)weak Hydrogen bonds (DNA)weak

Water Most important chemical compound in the living world: 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 2 Hydrogen (H) and 1 Oxygen (O) connected by covalent bonds

Polar O is negatively charged, H is positively charged leading to the “magnet-like” behavior of water molecules O is negatively charged, H is positively charged leading to the “magnet-like” behavior of water molecules

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

Review Why is water polar? Why is water polar?

Water’s Polarity leads to: 1. Stickiness: –Cohesion: attraction of water molecules to each other (sticks to itself) –Adhesion: attraction of H 2 O to other polar molecules (sticks to other polar molecules) –transpiration: water moves up the stems of plants and out leaves (against the pull of gravity) –Surface tension: skin-like behavior of water surfaces (ants trapped in a bubble)

Water’s Polarity leads to: 2. High Specific Heat –It takes lots of energy to vaporize water because the molecules stick together –This acts as a heat buffer for an organism’s body temp 3. Expansion when it freezes –Ice floats because it is less dense than water –Insulation of ponds, lakes, and oceans in winter 4. Great solvent for polar and ionic substances (e.g. sugars and salts)

Review Identify 4 unique properties of water. Identify 4 unique properties of water. Explain how polarity accounts for each of the properties you listed. Explain how polarity accounts for each of the properties you listed.