3. Water Basics Polar: part of a molecule is slightly positive, while another part is slightly negative Oxygen “hogs” electrons from hydrogen – 8 protons: 10 electrons – Negative charge Hydrogen without electrons – 1 proton: 0 electrons – Positive charge Creates hydrogen bonds where one water sticks to another

4. Red = Oxygen (negative)White = Hydrogen (positive) + +++ + ++ + ++ ++ ++ + + ++ ++ ++ + ++ + + ++ + +++ + ++ + + ++ + + + + + + + ++ ++ ++ + --- -- - --- - -- - -- --- -- -- ----

5. Water Properties Energy needed to break H bonds High specific heat: Resists temp changes – Helps to maintain a constant body temp Cohesion: polar water molecules attracted to other polar water molecules (see bug picture) Adhesion: polar water sticks to other molecules

6. Solutions Solution: mixture where 1 substance dissolves in another 2 parts to a solution 1) Solute: substance that dissolves in a solution Atoms, ions, molecules 2) Solvent: substance in which the solute is dissolve Usually water Ex: Human blood – Solvent: Plasma (watery part of blood) – Solutes: Carbs, proteins, sugars, etc…

7. pH scale measures the amount of H+ ions Some molecules release H+ ion when dissolved H+ ions accumulate (acids) Some molecules release OH- (hydroxide) ions when dissolved OH- (hydroxide) ions accumulate (bases) pH balance vital to life (homeostasis) – Ex: Proteins break apart when outside normal pH pH Scale

8. The higher the [H+], the lower the pH! Ex: Lemon juice has a higher [H+] than the soap in your bathroom. Which has a higher pH? H+

9. Red Cabbage pH Indicator

10. REview 1) Name 4 basic features of water. 2) Which water property explains that one atom is positively charged, while another is negatively charged? 3) How does cohension and adhesion differ? 4) Which is a stronger acid? Substance A with a pH of 5 or substance B with a pH of 3? 5) Which has more H+ ions? Substance A with a pH of 5 or substance B with a pH of 3? 6) Which has more OH- ions? Substance A with a pH of 5 or substance B with a pH of 3? 7) What is the solute and solvent of blood?