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प्रश्न
Give the reason why the following is considered as chemical changes.
Sulphur when burnt in air evolves a gaseous acidic product.
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उत्तर
Is a chemical change as sulphur (yellowish-green) on burning produces SO2 gas which is acidic in nature and a new substance with new properties is formed
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संबंधित प्रश्न
Explain the following giving an example.
Pure substance
Tick the most appropriate answer.
5. Photosynthesis requires
- heat energy.
- wind energy
- sunlight.
- sound energy
A physical change is temporary. Explain.
Write true or false
Melting of ice is a physical change.
State one instance where water undergoes a physical change and one in which it undergoes a chemical change.
Give three reasons why melting of wax, is considered a physical change while burning of a candle, a chemical change.
Give reasons why – separation of mixtures e.g. iron from a mixture of iron and sulphur is a physical change, but heating a mixture of iron and sulphur is considered a chemical change.
Match the following
| Sr. No. | A | B | C |
| 1. | Melting | Change of state from liquid to solid | Ticking of clock |
| 2. | Condensation | Change of state from liquid to gas | Formation of ice cube |
| 3. | Evaporation | Change of state from solid to liquid | Collecting flowers |
| 4. | Freezing | Change of state from gas to liquid | Ice cube to water |
| 5. | Periodic change | Occurs at irregular time intervals | Water to steam |
| 6. | Non-periodic change | Occurs at regular time intervals | Steam to water drops |
Ice, water and water vapour look different and display different ______ properties but they are ______ the same.
Give an example to justify the statement that physical changes can be reversible as well as irreversible.
