1. Structure of Water H & O covalently bonded together. H & O covalently bonded together. Water is polar Water is polar It has a slightly positive charge on one end and a slightly negative charge on the other. It has a slightly positive charge on one end and a slightly negative charge on the other.

2. Properties of Water Cohesion: the tendency of molecules of the same kind to stick to one another. Cohesion: the tendency of molecules of the same kind to stick to one another. Adhesion: the attraction between unlike molecules. Adhesion: the attraction between unlike molecules. Why would these properties be important to plants? Why would these properties be important to plants?

3. Water H 2 O  H + + OH - The breaking apart of water molecules into two ions is known as dissociation.

4. OH - : hydroxide ion (basic) H + : hydronium ion (acidic)

5. Acids and Bases Most chemical reactions in living organisms take place in water. (aqueous) Most chemical reactions in living organisms take place in water. (aqueous) Water can dissociate into two ions. Water can dissociate into two ions. a positive hydrogen ion (H + ) (hydronium), and a positive hydrogen ion (H + ) (hydronium), and a negative hydroxide ion (OH - ) a negative hydroxide ion (OH - ) If the number of hydrogen ions (H + ) equals the number of hydroxide ions (OH - ) then the solution is neutral (i.e.Pure water) If the number of hydrogen ions (H + ) equals the number of hydroxide ions (OH - ) then the solution is neutral (i.e.Pure water) H 2 O H + + OH - H 2 O H + + OH -

6. Acids and Bases Acids and bases are measured on the pH scale. The pH scale runs from 0 - 14. Acids and bases are measured on the pH scale. The pH scale runs from 0 - 14. A pH of 7 is neutral A pH of 7 is neutral A pH less than 7 is acid (the lower the number the stronger the acid). A pH less than 7 is acid (the lower the number the stronger the acid). A pH greater than 7 is basic (the higher the number the stronger the base). A pH greater than 7 is basic (the higher the number the stronger the base).

7. Acids and Bases 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 STOMACH JUICE LEMON JUICE COLA TOMATO JUICESHAMPOO SALIVAHUMAN BLOOD SEA WATERBAKING SODA AMMONI A BLEACH LYE NEUTRAL INCREASINGLY ACIDINCREASINGLY BASIC pH SCALE

8. How do you think that tums work? Weak base + Hydrochloric acid  Salt and Water. Example: Mg(OH)2 + 2HCI --> MgCI2 + 2H2O