1. Acids and Bases

2. Water… A recap Water’s chemical formula is H 2 O Two Hydrogen atoms covalently bonded to an Oxygen atom Oxygen has a stronger pull on electrons (- charge), so Oxygen becomes slightly NEGATIVE Since Hydrogen has a weaker pull, (less time with the – charged particle, Hydrogen is slightly POSITIVE This creates an effect known as polarity Attraction between slightly positive and slightly negative charges forms Hydrogen bonds

3. Polar Water Molecule

4. Dissociation Water sometimes breaks down into H + and OH - ions These ions are incredibly reactive In pure water, these ions recombine to form H 2 O

5. Dissociation of Water When water is dissolved in water, the H + ions will combine to form H 3 O + … This is called a Hydronium ion

6. Acids Other chemicals can donate H + ions These chemicals are called acids HCl (Hydrochloric acids) are very strong and break into H + and Cl - very willingly Solutions with more H + ions are acids

7. Bases Compounds that accept H + ions are called bases For example, NaOH (sodium hydroxide) will lose its OH - group, which combines with lose H + ions to form H 2 O This reduces the H + concentration and increases the OH - group Solutions with more OH - ions are called bases

8. pH scale Used to describe how basic or acidic a solution is pH stands for “Potential of Hydrogen” Scale runs from 0-14 0- highly acidic (more H + ions) 7- neutral (equal H + and OH - ions) 14- highly basic (more OH - ions) Each change in the level is ten fold For example: Lemon juice has a pH of 2 Grapefruit has a pH of 3 Lemon juice is ten times more acidic than grapefruit Has ten times more H + ions than grapefruit juice

9. pH scale

10. Dangers! Cells can be damaged by acids and bases Disrupt the chemical composition of the cell membrane Denature proteins and prevent them from working Buffers Help the body maintain homeostasis (balance) These chemicals accept loose H + to form neutral water Help resist changes when acids are added to a system

11. Blood Your blood has a healthy pH of 7.4 If the pH drops to 7 or raises to 7.8, the organism will not survive for more than a few minutes Buffers in your blood help prevent this from happening