Classify each of the following, as a physical or a chemical change. Give reasons.
(a) Drying of a shirt in the sun
(b) Rising of hot air over a radiator
(c) Burning of kerosene in a lantern
(d) Change in the color of black tea on adding lemon juice to it
(e) Churning of milk cream to get butter.

AcademicChemistryNCERTClass 9

(a) Drying of the shirt in the sun is a physical phenomenon because there are no chemical reactions or any chemical changes involved in this process

(b) Rising of hot air over the radiator is a physical change. Water in a radiator converts to vapours. Hot air becomes lighter and rises.

(c) Burning of kerosene in a lantern is a chemical change because kerosene burns by using atmospheric oxygen and produces carbon dioxide.

(d) Change in the colour of black tea on adding lemon juice to it is a chemical change. Lemon juice is a source of citric acid, ascorbic acid and malic acid. This acid reacts with the flavin antioxidants present in black tea to change the colour of the tea.

(e) Churning of milk cream to get butter is a physical change as there is no involvement of chemical reaction. Here the principle is of centrifugation which turns the milk cream into butter.
raja
Updated on 10-Oct-2022 13:29:40

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