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प्रश्न
Give a reason why
Freezing of water is a reversible change while burning of a candle – an irreversible change.
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उत्तर
Freezing of water is reversible change as on heating frozen ice changes to water by heating.
Burning of a candle is irreversible change as on reversing the conditions we can not get candle back out of CO2, water vapours and wax vapours.
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संबंधित प्रश्न
Classify the following as chemical or physical change:
Dissolving common salt in water.
Tick the most appropriate answer.
4. Chemical changes involve
- change in shape.
- change in size.
- change in molecular composition.
- none of these
Write true or false for the statement
Decomposition of leaves is a fast change.
A physical change is temporary. Explain.
Tick (√) the correct alternative from the choice given for the following statement.
A substance which can not sublime is
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.
Classify the Following as a Physical Or a Chemical change.
Glowing of an Electric Bulb
State why addition of sodium chloride to water is considered a physical change, while addition of dilute sulphuric acid to zinc is considered a chemical change.
Select the chemical changes from the following list of changes
The crystallisation of salt from its solution.
Stretching gold coin into a ring is a ______ change.
