Question

Match the columns

I	II
a) Physical changes	(i) Curdling of milk
b) Chemical changes	(ii) Demagnetization of magnets
	(iii) Digestion of food
	(iv) Crystallization of substance
	(v) Rusting of iron

Answer 1

Hint: Changes in energy can be easily noted by a particular chemical change or physical change. Many changes happen naturally like in an environment for example evaporation of water, condensation, rainfall etc. During some chemical reactions the old bonds get broken and new bonds are formed.

Complete answer:
To find out which one is physical change or chemical change we have to go through the concept of what is physical and chemical change. During the physical change arrangement of the molecules is disturbed due to which they change their state. Molecular composition remains the same during this change.
As from the discussion we can consider that a physical change involves only change in physical state whereas a chemical change results in the formation of new substances.
Crystallization of substance and Demagnetization of magnets comes under the physical change as physical properties of the substance get changed while its chemical composition remains unchanged.
Curdling of milk, Digestion of food and Rusting of iron comes under chemical changes in which chemical properties of the substance also changes.

Hence the correct answer is a) (ii), (iv) and b) (i), (iii) and (v) .

Note:
The change in which the molecular composition is completely changed and a new product is formed in chemical change and it creates a new product while physical change will not create a new product.