Chemical Properties of water Chapter 6 Remember Cornell

Chemical Properties of water Chapter 6

Remember Cornell Notes! Con/def/ques Nts/Ans

Observations • Beaker 1 before: – Write observation • Beaker 1 after: – Write observation • Why? ? ?

Polarity • What is the empirical formula for water – H 2 O • Structural formula? – O H H • H-O bond called Covalent Bond – Atoms sharing electrons – Very stable molecules • Lopsided: – O atom attracts the shared electrons to its large nucleus – Hydrogen positives towards outside – Like a magnet! • Such positive and negative charged ends is called polarity and are found in polar molecules

Polarity con’t • Hydrogen bonds: – Definition – Picture (6 -7 figure) • Dipolar molecules – Definition – Picture (6 -6)

Effects of Hydrogen bonding Essential to the properties of water. 1. Liquid Water: • • Bonds hold molecules together more energy needed to form gas. Draw picture (not in book!) 2. Cohesion/Adhesion: • Water molecules stick together (cohesion – sticking together) • Gives more organized structure then most liquids • Also sticks to other surfaces (adhesion – sticking to different) • Draw picture (not in book!)

Effects of Hydrogen Bonding Con’t 3. Viscosity: • • Fluid (g or l) resisting flow Changes by temperature Example: oil in cool vs. hot pan Water: more viscosity • Cools: viscosity rises more than other liquids H bonds • resist heat moving molecules Important? : • cool waters, high viscosity, drifting aquatic animals use less energy to keep from sinking • Swimming animals use more energy moving through it • Draw Picture!

Effects con’t 4. Surface Tension: • • water’s resistance to objects attempting to penetrate its surface Cohesion at surface allows for surface tension Large organisms: not much affect Small organisms: huge affect Jesus Lizard, boatman (water striders), plankton Current study: air-ocean interaction at surface. How does surface tension affect gas exchange? Ocean’s can absorb CO 2 surface tension affects in some way help with climate change? Pollution that affects: • Detergents/soaps: reduce hydrogen bonding, surface tension down. How affect Jesus Lizard? Draw picture!

Effects Con’t 5. Floating Ice • • • Most substances cool solid sink or heat gas float Water is different! It does become more dense as cool and less dense as heat but stops at a certain point Hydrogen bonds cool crystal structure more space than liquid water. Thus, more volume than liquid water and less dense, so floats on top Important? • Insulates water below retain heat remain liquid below • Think: More solid water, cooler climate! Thus, no life Draw Picture!