100+ Transformation of Substances Question Answer - 1

Question: 1

Define oxidation?

A chemical reaction which involves addition of oxygen to a substance or removal of hydrogen from a substance is called oxidation.

Example: Rusting of iron and burning of sulphur are oxidation reactions.

Question: 2

What are the conditions for chemical reactions?

Some reactions require heat. Some require light. Some reactions may require pressure.

Examples – Photosynthesis require sun light. Ammonia is manufactured from hydrogen and nitrogen under high pressure and high temperature.

Question: 3

What is an exothermic reaction?

A reaction in which heat is released is called exothermic reaction. When dry lime is added to some water in a beaker, the water gets heated during the reaction. This is an example for exothermic reaction.

Question: 4

What are chemical changes?

Chemical changes are the changes in which new substances are formed. The component of the substance cannot be got back easily.

Example – Rusting of iron

Question: 5

Define physical changes?

Physical changes are the changes in which no new substances are formed. The components of the physical change can be got back easily.

Example Freezing, Evaporation.