NCERT 6th Class (CBSE) Science: Changes Around Us

Question: Breaking of tumbler and burning of paper are change in which we cannot get back the original substances what is the difference between these two changes?

Answer: Breaking of glass tumbler is physical change as no new substance has formed and the broken tumbler remains glass only. Burning of paper is change because after burning the paper is changed into ash a new substance has formed.

Question: What kind of change is cooking of food? Why?

Answer: Cooking of food is chemical change as after cooking the raw vegetables become cooked and cannot be converted back into raw vegetables. After cooking properties like softness, taste, colour change due to change in the molecules.

Question: Growth is increase in size. Is it a physical or chemical change? Give reasons?

Answer: Growth is a life process that take due to so many chemical changes that take place in the cells.

Question: Explain the difference between physical and chemical changes, give on example each.

Answer: Physical change:

1. Only the physical appearance changes.
2. They are mostly reversible.
3. Energy is may or may not be absorbed or released.
4. They are temporary.
5. For Eg: melting of chocolate boiling.

Chemical change:

1. A new substance is formed.
2. They are mostly irreversible.
3. Energy is either absorbed or released.
4. They are permanent.
5. For Eg: Burning, cooking.