Acids and Bases

When we think of acids and bases we tend to think of chemistry lab acids and bases like But we are surrounded by acids and bases in the world. Most of them are weak. Acids cause: Lemons to be sour Acid rain to eat away at sculptures Cavities in your teeth Digestion of food in your stomach Ants to give you a nasty bite

What are Acids and Bases? Properties of an Acid Tastes sour Turns litmus paper red Has a pH of less than 7 Lemon juice and vinegar are acids Properties of a Base Taste bitter and have a slippery feel Turns litmus paper blue Has a pH greater than 7 Bases that are soluble (dissolve in water) are called alkalis Most hand soaps and drain cleaners are bases

What are Acids and Bases? Hydrochloric acid, HCl and sulfuric acid H2SO4 are very corrosive Carbonic acid is used in fizzy drinks Ethanoic acid is in vinegar Citric acid is in oranges and lemons Sodium hydroxide, NaOH is very corrosive and is known as caustic soda Calcium hydroxide Ca(OH)2 forms limewater when dissolved in water

Carbonated soft drinks contain carbonic acid Tea contains tannic acid Carbonated soft drinks contain carbonic acid Fruit contains citric acid

Acid rain (nitric /sulfuric acid) corroding a limestone sculpture. Strenuous exercise causes a buildup of lactic acid in muscle tissue

Acid Rain Acid rain kills trees and aquatic life

Universal indicator H2SO4 pH = 1 turns red Lemon juice pH = 3 turns orange Rainwater pH = 6 turns yellow Window cleaner pH = 10 turns blue NaOH pH = 14 turns navy

pH Scale The pH scale is a way of expressing the strength of acids and bases The pH scale goes from 0 to 14 Under 7 = acid 7 = neutral Over 7 = base

pH Scale

Indicators These are chemicals that change colour in the presence of an acid or a base. There are a number of different indicators that change color at different pH’s.

Making salt Cl + OH H Na HCl + NaOH  NaCl + H2O Acids and alkalis react together to form a neutral salt and water A salt is formed when a metal ion replaces the hydrogen in an acid Cl + OH H Na HCl + NaOH  NaCl + H2O

Sodium hydroxide and litmus indicator solution OC38 Burette Retort stand Hydrochloric acid Conical flask Sodium hydroxide and litmus indicator solution

Acids with Carbonates 2HCl + CaCO3  CaCl2 + H2O + CO2 Acid + Carbonate  Salt + Water + Carbon Dioxide 2HCl + CaCO3  CaCl2 + H2O + CO2