[Science Form 2] Two Important Solutions

Acids and alkalis are two important kinds of solutions.

Acid comes from the latin word acidus, which means "sharp" or "sour". Some of the acids can be found in:

• Lemons/lemon juice, which contains citric acid,
• Oranges, which contain ascorbic acids,
• Ant and bee stings, which contain methanoic acid,
• Tea, which contains tannic acid,
• Soft drinks, which contain carbonic acid,
• Vinegar, which contains ethanoic acid, and
• Our body, which contains small compounds called amino acids.

There are different strengths of acids. The number of H⁺ ions formed in the solution determines the strength of an acid.

Examples of strong acids: hydrochloric acid, sulphuric acid and nitric acid.

Examples of weak acids: ethanoic acid, citric acid and carbonic acid.

Alkali comes from the Arabic word al-qaliy, which means "the ashes". Alkalis are present in many cleaning substances used in our homes today, especially in kitchen cleaners like oven spray, floor cleaners and creams for sinks.

Kitchen cleaners are alkaline because they contain ammonia or sodium hydroxide, which attack grease. Other common alkalis include sodium hydroxide, potassium hydroxide, calcium hydroxide and ammonia.

There are different strengths of alkalis. The number of OH^- ions in the solution determines the strength of an alkali.

Some examples of strong alkalis are calcium hydroxide, sodium hydroxide and potassium hydroxide, while the most recognisable and common weak alkali is ammonia.