Paheli went to the market to buy sarees for her mother. She took out a thread from the edge of the two sarees shown by the shopkeeper and burnt them. One thread burnt with a smell of burning hair and the other burnt with the smell of burning paper. Which thread is from a pure cotton saree and which one from a pure silk saree? Give reason for your answer.

The thread which burnt with the smell of burning hair is from pure silk saree. The reason for this conclusion is that both hair and silk are protein fibres. Thus silk fibre on burning gives the same smell as a hair strand.

The thread which burnt with the smell of burning paper is from pure cotton saree. The reason for this conclusion is that both cotton and paper are obtained from plants. Both are made up of carbohydrates and thus on burning gives same smell.