1 Acids and Bases

2 Taste of Acids and Bases Have you ever taken a bite out of a lemon? Lemon juice is an acid, and acids can taste sour. Baking soda has a bitter taste that most people do not like. Baking soda is a base, and bases can taste bitter. Water is not an acid or a base, it is neutral and has no particular taste. Please do not ever taste strong acids or strong bases or any other chemicals that are not food! Acid Base Neutral

3 How Do Acids and Bases Feel? If you are slicing lemons and some of the juice gets into a cut on your finger, it stings. Acids sting! If you have ever spilled bleach or soap on the floor, you may have noticed that it is slippery. Bases are slippery. Please do not ever touch strong acids or strong bases because they can be harmful to your skin and may damage sensitive tissues such as your eyes. A neutral substance such as water is a good choice for cleaning up acids and bases because it does not sting and it is not slippery. Acid Base Neutral

4 Chemical Considerations… Acids –Dissolve metals (like tomato sauce in an aluminum pan) –Denature proteins (meat tenderizer) –Make cavities (bacterial acid on the teeth) Bases –Dissolve and surround fatty acids Dilute bleach solution destroys bi-lipid skin cell membranes. –Break up oils and dirt Soap is used because water alone cannot break down oils.

More Acidic H + More Basic OH- Neutral 6 Litmus paper is used as an indicator for acids and bases. Acidic turns blue litmus  to red Basic turns red litmus  to blue

6 What is pH? pH The abbreviation pH stands for “the power of Hydrogen.” H+H+H+H+ H+H+H+H+ H+H+H+H+ H+H+H+H+ H+H+H+H+ H+H+H+H+ H+H+H+H+ H+H+H+H+

7 O H OH - If there are more H + than OH-, then the chemical is an acid. If there are Less H + than OH-, then the chemical is a base. If there are equal amounts of H + and OH-, then the chemical is neutral. O H OH - O H H+H+H+H+ H+H+H+H+ H+H+H+H+

8 Bases and acids neutralize each other. Mixing equal amounts of similar strength acids and bases produces a neutral substance. +  Neutralization of Acids and Bases

9 Electrolytes Because dissolved acids and bases have positive and negative ions, they are electrolyte solutions and conduct electricity.

10 Acid Rain Rain or any other precipitation is naturally acidic because it mixes with carbon dioxide and forms carbonic acid. However, gases released into the atmosphere from burning fuels such as coal and oil increase the acidity in rain. This causes “acid rain” which can kill animals that live in water. Acid rain can also kill plants which rely on rain as their water source.

11 Acid and Bases Vocabulary ALKALI –Another word for base STRONG ACID –An acid which has a very low pH (0-4) STRONG BASE – A base which has a very high pH (10-14) WEAK ACID –An acid that only partially ionizes in an aqueous solution –That means not every molecule breaks apart. –It usually has a pH close to 7 (3-6). WEAK BASE – –A base that only partially ionizes in an aqueous solution –That means not every molecule breaks apart. –It usually has a pH close to 7 (8-10).