1. 25.1 Acids, Bases, and pH Key Question: What is pH? *Read text section 25.1 AFTER Investigation 25.1

2. 25.1 Acids, Bases, and pH Your stomach secretes one of the stronger acids, hydrochloric acid (HCl). As acidic solutions of digested food leave your stomach, other organs in your digestive system secrete bicarbonate, a base. The added base neutralizes the strong, corrosive acid.

3. 25.1 Acids, Bases, and pH Acids An acid is any substance that produces hydronium ions (H 3 O+) when dissolved in water. They react with metals to produce hydrogen gas (H 2 ) They change the color of a plant dye (called litmus) from blue to red.

4. 25.1 Acids, Bases, and pH Bases A base is any substance that produces hydroxide ions (OH-) when dissolved in water. While you should never touch a laboratory chemical, the bases you use every day such as soap, have a slippery feel. They change the color of litmus from red to blue.

5. 25.1 Electrolytes and non-electrolytes Electrolytes conduct current. All acids and bases are electrolytes because they contribute ions to a solution. Other chemicals do not form ions when they are dissolved in solution. They are called non- electrolytes. Non-electrolytes are not acidic or basic. Sugar dissolved in water is an example of a non-electrolyte.

7. 25.1 Acids and bases in your body It is very important for your blood pH to stay within the normal range. The rate at which you breathe controls the concentration of carbon dioxide in your blood.

8. 25.2 Acid Rain Any rain, snow, or fog that has a pH lower than 5.6 is called acid rain or acid precipitation.

9. 25.2 Acid Rain Acid rain is harmful to natural environments because most life and life processes function in nearly neutral environments. Acid rain reduces the amount of calcium in the soil.

10. 25.2 Catalytic converter A catalytic converter is a device that converts nitrogen oxide to nitrogen gas (N 2 ) and oxygen (O 2 ) before these emissions enter the atmosphere.

12. 25.2 Acid Rain Key Question: What is acid rain? *Read text section 25.2 BEFORE Investigation 25.2

13. 25.2 Acid Rain Key Question: What is acid rain? *Read text section 25.2 BEFORE Investigation 25.2