1. AP Biology Ch 3 - Water

2. 3.1 The Polarity of Water Molecules Results in Hydrogen Bonding H 2 O – 2 hydrogen, 1 oxygen Difference in electronegativity results in polar bonds Asymmetric shape of molecule results in polar molecule Directions: Cut out your water molecules. Shade the positive side red and the negative side black

3. 3.1 The Polarity of Water Molecules Results in Hydrogen Bonding Interactions between the positive and negative ends of the molecules are called hydrogen bonds Molecules of water are constantly moving, hydrogen bonds constantly forming and breaking 4 emergent properties of water result from hydrogen bonding

4. 3.2 Four Emergent Properties of Water Property 1: Cohesion Explain: Cohesion – Cohesion – Adhesion – Surface tension Importance in Biology (examples):Adhesion

5. 3.2 Four Emergent Properties of Water Property 1: Cohesion Explain: Cohesion – molecules bond to each other Adhesion – Molecules bond to another substance Surface tension – how difficult it is to break the surface of a liquid Importance in Biology: Water pulled up tree through transpiration (cohesion) Water held inside plants (adhesion)

6. 3.2 Four Emergent Properties of Water Property 2: Moderation of Temperature Explain: Water molecules being heated – Kinetic energy (why does water have a – Heat vs temperature high specific heat?) – Specific heat – Water as a heat sink Importance in Biology:

7. 3.2 Four Emergent Properties of Water Property 2: Moderation of Temperature Kinetic energy – energy of motion Heat – total kinetic energy Temperature - average kinetic energyy – Example: Swimmer has higher temp, pool has higher heat Specific heat – amount of heat absorbed to raise temp of 1 g by 1 0 C Water has such a high specific heat because so much energy goes into breaking the hydrogen bonds

8. 3.2 Four Emergent Properties of Water Property 2: Moderation of Temperature Importance in Biology: Large bodies of water – cool during the day, warm at night Regulate the temp of everything around them – prevent extreme fluctuations Stable ocean temps Organism’s bodies made of water – prevents extreme fluctuations

9. 3.2 Four Emergent Properties of Water Property 3: Insulation by Ice Explain: Water as a liquid – water density as liquid vs solid – Hydrogen bonding as a liquid vs a solid Importance in Biology:Water as solid

10. 3.2 Four Emergent Properties of Water Property 3: Insulation by Ice Water is one of a few substances that is less dense as a solid As molecules slow down and get closer together, hydrogen bonding results in crystalline lattice Importance in Biology: Cold bodies of water freeze over top, not from the bottom up Insulates water below, protecting life

11. 3.2 Four Emergent Properties of Water Property 4: Solvent of Life Explain: Hydration shell – solvent, solute – Aqueous solution – Hydration shell – What will dissolve in water? – Hydrophobic vs hydrophilic Importance in Biology:

12. Property 4: Solvent of Life Explain: – solvent, solute - Solute dissolves in solvent – Aqueous solution – water is the solvent – Hydration shell – water molecules surround solute particles because of charges and separate them – What will dissolve in water? – Ionic compounds, polar molecules – Hydrophobic (affinity for water) vs hydrophilic (repel water)

13. Property 4: Solvent of Life Importance in Biology: Allows chemical reactions that sustain life! Membranes composed of hydrophobic molecules allow internal environment to be different than external environment 3.2 Four Emergent Properties of Water