Acid rain contains sulfuric acid and nitric acid. Calcium hydroxide (a base) is used to make cement. Sodium hydroxide (a base) is used in the manufacture of soap. Many cleaning products are bases.
Activity Testing substances with litmus paper
1. Place a small amount of lemon juice or vinegar into a beaker. 2. Place a small amount of water and baking soda into a beaker. 3. Test each substance with a piece of blue litmus paper and a piece of red litmus paper. 4. Write down any colour changes that you observe.
Results Use a table like this to record your results:
Effect on red litmus paper
Lemon juice/ vinegar
Baking soda
Questions 1. What effect do acids have on blue litmus paper? 2. What effect do bases have on red litmus paper?
Acids
l l l
l l l l
Acids are substances that turn blue litmus red. They have a sour taste. Concentrated acids are very corrosive.
Bases
Bases are substances that turn red litmus blue. Bases have a soapy feel when they react with water. Bases that dissolve in water are called alkalis. Concentrated bases are very corrosive.
Fig. 3 Acids turn blue litmus paper red.
Fig. 4 Bases turn red litmus paper blue.
Corrosive Can damage substances it comes into contact with.
