Question 1 What is a physical change. Give example?
Question 2 What is a chemical change. Give example ?
Question 3 Give the main differences between physical and chemical change?
Physical and Chemical Changes
The changes in which no new substance are formed are called physical changes.
In a physical change, the substances involved do not change their identity. They can be easily returned to their original form by some physical changes.
For Example : Freezing of water, Boiling of water, Condensation of steam, Making a solution, Glowing of electric bulb, stretching of rubber band, cutting or tearing a piece of paper etc.
The changes in which new substance are formed, are called chemical changes.
In a chemical change, the substances involved change their identity i.e. they get converted into entirely new substance.
For Example : Burning of magnesium ribbon, Rusting of iron, Formation of curd from milk, Cooking of food etc.
|(1) No new substance is formed in the physical change.
|A new substance is formed in a chemical change.
|(2) Physical change is temporary change.
|A chemical change is a permanent change.
|(3) Physical change is reversible.
|Chemical change is irreversible.
|(4) Very little heat or light energy is usually absorbed or given out in a physical change
|A lot of heat or light energy is absorbed or given out in a chemical change.
|(5) The mass of a substance does not alter in a physical change
|The mass of a substance does alter in a chemical change.