Presentation on theme: "Water Chapter 3. Water Life began in water 2/3s of an organisms body Organisms grow or reproduce in a water-rich environment."— Presentation transcript:
Water Chapter 3
Water Life began in water 2/3s of an organisms body Organisms grow or reproduce in a water-rich environment.
Water Molecule Covalent bonding Oxygen is more electronegative Polar molecule Polarity of water underlies its chemistry Chemistry of life.
Fig. 3-2 Hydrogen bond – H + H O – – –
Properties of water Cohesion: Attraction between water molecules Responsible for surface tension of water
Properties of water Adhesion: Attraction of water between other molecules Capillary action
Properties of water Moderation of water temperature Water is a liquid at moderate temperatures Specific heat: Amount of heat needed to a raise 1 gram of a substance 1 0 Celsius Waters specific heat is 1 calorie/gram/ 0 C (4.18Joules)
Properties of water Evaporative cooling Heat of vaporization: Amount of heat needed to change 1 gram of a substance from a liquid to a gas. 586 Calories (2260 Joules)
Properties of water Ice floats Less dense
Fig. 3-6a Hydrogen bond Liquid water Hydrogen bonds break and re-form Ice Hydrogen bonds are stable
Properties of water Solvent Water surrounds ionic & polar molecules Table salt or sugar Aqueous solution Molarity
Buffer Substance helps maintain a balanced pH Accepts H + ions when excess Donates when there are too few.
Buffer Blood pH is approximately 7.4. Bicarbonate ion helps maintain the pH of the blood. Blood acidosis: pH drops 0.2 to 0.4 points on the pH scale Blood alkalosis: pH goes up 0.2 to 0.4 points on the pH scale