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 colour of black tea by adding lemon juice to it. Churning of milk cream to get butter.
ScienceClass 9CBSEAnswered 27 Mar 2026
Answer
- Solution:
- 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.
- Rising of hot air over the radiator is a physical Water in a radiator converts to vapours. Hot air becomes lighter and rises.
- Burning of kerosene in a lantern is a chemical change because kerosene burns by using atmospheric oxygen and produces carbon dioxide.
- 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 This acid reacts with Flavin antioxidants present in black tea to change the colour of the tea.
- Churning of milk cream to get butter is a physical change as there is no involvement of a chemical Here, the principle is centrifugation which turns the milk cream into butter.
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