Question

Which of the following is a physical change?
(A) Magnetisation of iron
(B) Curdling of milk
(C) Burning of a candle
(D) Cooking of food

Answer 1

Hint: As we know that the term physical means daily life practices in which changes are made by changing the state of matter but not in change of matter such as icing of water in which the liquid state of water is changed into solid state of water.

Complete answer:
The physical changes are those changes which do not give different products when the reaction occurs. In this change, the state of matter only changes but matter does not change as when the state of water changes from liquid state to solid state is known as physical change. As we can see the water molecule still has the same composition.
Let’s move towards options
In the option (A), the Magnetisation of iron is done by the rubbing of iron with any magnet which generates the charge on the iron So, this does not give any change in the iron therefore it is a physical change.
In option (B), the curdling of milk is the product of the reaction between milk which has protein and curd which has lactic acid composition so both react and give curd as product. Therefore, this is not a physical change.
In the option (C), Burning of candle is also not a physical change because the candle reacts with oxygen.
In the option (D), Cooking of food is also not a physical change because it gives a new product. Hence it's a chemical change.
Hence, we can say that magnetisation of iron is a physical change.

Therefore the correct option is (A).

Note: When a substance undergoes a physical change, its composition remains the same but in a chemical change the molecular composition is changed entirely.