1 Acids and Bases

2 Acids React with certain metals to produce hydrogen gas. React with bicarbonates to produce carbon dioxide gas Have a bitter taste Feel slippery. Many soaps contain bases. Bases

3 Properties of Acids þ Produce H + ions in water Taste sour þ Corrode metals þ Good Electrolytes þ Ions used to transmit signals throughout the body water þ React with bases to form a salt and water þ pH is less than 7 þ Turns blue litmus paper to red “Blue to Red A-CID”

Some Common Acids HC 2 H 3 O 2 acetic acidin vinegar HClhydrochloric acidstomach acid H 3 C 6 H 5 O 7 citric acidfruits H 2 CO 2 carbonic acidsoft drinks H3 2 PO 4 phosphoric acidsoft drinks

5 Properties of Bases  Generally produce OH - ions in water  Taste bitter, chalky  Are electrolytes  Feel soapy, slippery  React with acids to form salts and water  pH greater than 7  Turns red litmus paper to blue “Basic Blue”

Some Common Bases NaOHsodium hydroxidelye KOHpotassium hydroxideliquid soap Ba(OH) 2 barium hydroxidestabilizer for plastics Mg(OH) 2 magnesium hydroxide“MOM” Milk of magnesia Al(OH) 3 aluminum hydroxideMaalox (antacid) Al(OH) 3 aluminum hydroxideMaalox (antacid)

The pH scale is a way of expressing the strength of acids and bases. Less than 7 = acid 7 = neutral Greater than 7 = base The pH values of several common substances are shown at the right. - Many common foods are weak acids - Some medicines and many household cleaners are bases.

pH testing There are several ways to test pH Blue litmus paper (red = acid) Red litmus paper (blue = basic) pH paper (multi-colored) **what we’ll use pH meter (7 is neutral, 7 base) Universal indicator (multi-colored) Indicators like phenolphthalein Natural indicators like red cabbage, radishes

pH indicators Indicators are dyes that can be added that will change color in the presence of an acid or base. Some indicators only work in a specific range of pH Once the drops are added, the sample is ruined Some dyes are natural, like radish skin or red cabbage