Be reactive

Q What are acids and alkalis? A: Acids and alkalis are two common types of aqueous solutions that we use every day.

Q What do you mean by ‘hazard’? A: Something that can be a source of danger is hazard.

Q What are hazard warning signs? A: A label containing pictures to warn you of the dangers of a chemical.

Q What are bases? A: Substances that can cancel the acidity of acids, so that they can become neutral are called bases.

Q What are alkalis? A: Bases which are soluble in water are called alkalis.

Q Name some alkalis that are used in school Laboratories. A: Sodium hydroxide, calcium hydroxide and ammonia solution.

Q Write properties of alkalis. A: 1) All alkalis are soapy to touch. 2) Turns red litmus paper to blue. 3) Have a pH value greater than 7. 4) Have a bitter taste. 5) Are usually corrosive and cause bleaching. 6) Are good electrical conductors. 6) React with acids to form salt and water only.

Q Name some alkalis and write their uses. AlkalisUses Sodium hydroxide ( caustic soda) Making soaps, washing powders and drain cleaners. Potassium hydroxide ( caustic potash) Making paint removers and dyes for fabrics. Calcium hydroxide Making mortar and reducing acidity of soil. Aqueous solution ( Ammonia solution) Making fertilisers and cleaning liquids Magnesium hydroxideMaking indigestion tablets and ‘milk of magnesia

Q How does shampoo make our hair soft and silky? A: Shampoo containing strong alkalis can damage our hair and make it look dull. Therefore, conditions are used to neutralise the alkali and make the hair soft.