Obj: Students will be able to describe an acid or a base. Acids and Bases Obj: Students will be able to describe an acid or a base.

Acids and Bases are Everywhere! Every liquid you see will probably be either an acid or a base. Exception: distilled water (just H2O) Acids: Amino acids in our bodies Citric acids in fruits Bases: Baking soda mixed with water

Acids A solution that can donate a hydrogen ion—a proton (H+)—to another substance. general form is: HX Ex. HCl, H2SO4, HF, HBr… Generally the name “acid” is given to any substance that has a pH of less than 7.0 pH: general abbreviation for potential of Hydrogen The more H+ ions, the stronger the acid will be.

Properties of Acids Taste sour (grapefruit, vinegar, limes, etc.) React strongly with metals Ex. when acids react with Mg, Zn, and Fe, hydrogen gas is produced. As a result, the metals seem to wear away. “Corrosive”  they “eat away” other materials Strong acids are dangerous and can burn your skin. (HCl, H2SO4, HF) Litmus paper – turns RED Video

Bases A solution that can accept a hydrogen ion—a proton—from another substance. generally the opposite of acids Ionic compounds (compound with a positive or negative charge) that break apart to form a negatively charged hydroxide ion (OH-) in water. Typically a base is any solution that has a pH greater than 7.0 The greater the concentration of OH- ions, the stronger the base will be.

Properties of Bases Taste very bitter (soaps, shampoos) Feel slimy or slippery (washing your hands) Can react violently with acids and cause burning on the skin In solution (mixed with water), will conduct electricity Litmus paper – turns BLUE

pH Scale Useful to identify a substance as acidic or basic. 0-4 strong acid 4.01—6.99 weak acid 7.00 = neutral 7.01—14 = base 7.01---10 = weak base 10.01—14 = strong base

Examples – Acidic or Basic? Soil pH 5.7 Soft drinks pH 3.9 Baking soda pH 8.4 Milk pH 6.4 Vinegar pH 2.6 Blood pH 7.4 Bleach pH 11.5 Ammonia pH 12.5 Acidic Acidic Basic Acidic Acidic Basic Basic Basic

Indicators A special type of compound that changes color as the pH of a solution changes. Can tell us the pH of a solution Red cabbage juice Litmus paper – most common indicator used by scientists Acids turn litmus paper red Bases turn litmus paper blue