Question

There are given some statement.in which of the following pair is a chemical change? *

A) Ice melts on heating, iron rust in moist air
B) Common salt dissolve in water, pulses change on cooking
C) Milk into curd, germination of seed
D) Ripening of fruits, melting of wax​

Answer 1

Answer:

9. Two natural indicators are given to you- A and B.

a. If we add indicator A to an acid, no change in colour is observed.

Which natural indicator is A ?

b. If we add indicator B to an acid, magenta colour is observed.

Which natural indicator is B ?

c. What will happen if indicator A is added to a basic solution ?

d. What will happen if indicator B is added to lime water ?

Answer 2

Among the given pairs, pair (c) Milk into curd and germination of seed, is a chemical change.

Explanation: Conversion of milk into curd is a chemical change as:

• Once milk changes into curd it cannot reverse its form again into milk, thus, it is an irreversible change.
• Chemical changes are irreversible changes.
• Also, when milk turns into curd, the taste changes, and a new substance is formed that is lactic acid.

Germination of seed is a chemical change as:

• When a seed germinates into a plant, it cannot turn from plant to seed again, so it is an irreversible process.
• Therefore, the germination of seed is also a chemical change.