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प्रश्न
Explain the term – ‘sublimation’. Is sublimation of naphthalene – a physical or a chemical change. Give reasons.
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उत्तर
It is the conversion of a solid – directly into gaseous (vapour) state and on cooling directly back to solid-state – without changing into a liquid state.
It involves a change of state-and hence it is a physical change.
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संबंधित प्रश्न
Classify the following as chemical or physical change:
Boiling of water to form steam.
Tick the most appropriate answer.
5. Photosynthesis requires
- heat energy.
- wind energy
- sunlight.
- sound energy
Write short answer.
Name two reversible changes.
Solve this crossword by using the clues that follow.
Across
1. Energy in the form of sunlight is absorbed by the green plants in this process.
4. The reddish-brown substance formed over iron in the presence of oxygen and moisture.
5. This change is permanent and irreversible.
6. The process in which a solid directly changes into gaseous state.
Down
1. It is the change that takes place in case of swinging pendulum of a clock.
2. Occurrence of this is a non-periodic change as well as a natural change.
3. It is a physical change
Given reason:
Cutting of a cloth piece is a physical change, though it cannot be reversed.
Give four difference between physical and chemical changes.
Name the following:
The term involved in the change of state from – ‘water to ice’ – which is a physical change.
Give a reason why
Change of seasons is a periodic change while the change of weather is a non-periodic change.
Select the chemical changes from the following list of changes
Vaporisation of water into water vapour.
Select the chemical changes from the following list of changes
Respiration in mammals.
