Give reasons for following changes are considered as chemical changes.
i) Potassium oxide is a strong alkali.
Answers
Answer:
Give reasons why the following are considered as chemical changes.
Copper Carbonate on heat gives copper oxide and carbon dioxide.
A bright light is seen to have evolved when a strip of magnesium is heated.
Sulphur, when burnt in air, evolves a gaseous acidic product.
An iron nail kept open in the atmosphere rusts.
A piece of magnesium strip is dropped into a beaker containing dilute hydrochloric acid.
1. Copper carbonate is green colored which gives copper oxide and carbon dioxide, which are new substances with new properties. This reaction is irreversible, hence it’s a chemical change.
2. When magnesium strip is heated it produces magnesium oxide in air. The composition changes to white powder and the change is irreversible. Hence, it is a chemical change.
3. Sulphur produces sulphur gas when burnt in air, this acidic product is new and changes the composition of sulphur. Hence, it is a chemical change.
4. Iron rust is a brown flaky powder formed after iron reacts with air, a new product with new properties is formed which are different from iron metal. Hence, it's a chemical change.

5.When a piece of magnesium strip is dropped in dilute hydrochloric acid, a new product hydrogen gas is evolved and Magnesium chloride has properties different from that of magnesium, which is irreversible and hence, it’s a chemical change.