The document discusses acids and bases. It defines acids as substances that ionize to form hydrogen ions in solution, and bases as substances that ionize to form hydroxide ions. Examples of acids include HCl and H2SO4, while examples of bases include NH3 and NaOH. The pH scale is used to measure how acidic or basic a substance is. Acids and bases react with each other through neutralization reactions to form salts and water. The formation of caves is also discussed, and involves the reaction of carbonic acid with calcium carbonate bedrock.

1. ACIDS AND BASES

2. Acids properties Conduct electricity (strong acids) Change blue litmus to red Have a sour taste React with bases to neutralize their properties React with active metals to liberate hydrogen pH values 6-0

3. Acids Acids are defined as: Substances which ionize to form hydrogen(+) ions in aqueous solution. (Arrhenius) Substances that act as proton donors (Bronsted-Lowry) or as electron-pair acceptors (Lewis) Examples HCl, H 2 SO 4

4. Bases properties Base properties Conduct electricity (strong bases) Change red litmus to blue Have a slippery feeling (like soap) React with acids to neutralize their properties pH values 8-14

5. Bases Bases are defined as: Substances which ionize to form hydroxide ions OH(-) in aqueous solution Substances that act as proton receptors (Bronsted-Lowry) or as electron-pair donors (Lewis) Examples: NH 3 OH , Na OH, Ca CO 3 , NaH CO 3 (baking soda) AMMONIAcleaner

6. pH Scale The pH scale is used to measure how acidic or basic is a liquid. pH measures the concentration of hydrogen ions (H+) and hydroxide ions (OH-). The scale goes from 0 through 14. Distilled water is 7, so is called neutral. lemon juice 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH Acidic Neutral Basic vinegar d water baking soda ammonia detergent

7. Indicators An indicator is a large organic molecule that works somewhat like a "color dye." Turns blue Stays same Red litmus paper Base Acid Indicator Pink Colorless Phenolphtalein Stays blue Yellow Bromophenol blue Stays same Turns red Blue litmus paper

8. Natural indicators There are natural indicators for acids and bases, and we may find them in our kitchen or garden! Red rose flowers Bougainvillea flowers Red cabbage Blue berries http:// tides.sfasu.edu :2006/cdm4/ item_viewer.php?CISOROOT =/ Digital&CISOPTR =1019&CISOBOX=1&REC=4

9. Acids and bases reactions The acids react with bases, forming salts ACID + BASE -> SALT + WATER H Cl + Na OH -> NaCl + H 2 O H - OH

10. Caves formation Cave formation is based on a chemical reaction between an acid and a base. This acid is carbonic acid ( H 2 CO 3 ), and the base is calcium carbonate ( CaCO 3 ), although it is not a direct reaction.

11. Caves formation Carbonic acid is formed by the reaction of rain water and carbon dioxide from soil. When the water is absorbed by the soil into the ground it reacts with the carbon dioxide present there: H 2 O + CO 2 -> H 2 CO 3 Water + carbon dioxide -> carbonic acid Carbonic acid is responsible for acid rain.

12. Caves formation The acid water reacts chemically with rocks made of the base calcium carbonate, called limestone , and dissolves them: H 2 CO 3 + CaCO 3 -> Ca + H 2 CO 3 Carbonic acid + calcium carbonate -> calcium + carbonic acid

13. Caves formation The calcium reacts with the hydrogen carbonate: Ca + HCO 3 -> CO 2 + CaCO 3 + H 2 O The carbon dioxide is given off into cave air to react again with rain water. Calcium carbonate is deposited, and water is formed. That’s the reason you will always see water inside the limestone caverns.

14. Caves formation These series of chemical reactions are very slow and take thousands of years to produce the characteristic stalagmites and stalactites of these caverns. http://tides.sfasu.edu:2006/cdm4/item_viewer.php?CISOROOT=/PPY&CISOPTR=81&CISOBOX=1&REC=1

15. Resources Animation of cave formation on Exploring Earth: http://www.classzone.com/books/earth_science/terc/content/visualizations/es1405/es1405page01.cfm?chapter_no=visualization