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प्रश्न
What is the difference between dissolution of sugar and burning of sugar ?
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उत्तर
1. Dissolution of sugar:
- When sugar is dissolved in water it disappears. It we taste the solution, the sugar is still present in dissolved form.
- If water is evaporated we get back the sugar.
- So it is a physical and reversible change.
2. Burning of sugar:
- Fire activates a chemical reaction between sugar and oxygen. The oxygen in the air reacts with the sugar as the chemical bonds broke.
- Energy is released in the form of smoke.
- So, burning a sugar is a chemical change.
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संबंधित प्रश्न
Tick the most appropriate answer.
3. Physical changes are
- permanent.
- periodic,
- temporary
- irreversible.
State four differences between physical and chemical changes.
State whether the following is physical or chemical changes.
mixing oil with water —
Write true or false
Cutting of paper into pieces is a chemical change.
Given reason:
Cutting of a cloth piece is a physical change, though it cannot be reversed.
Match the examples of changes in List I with the correct type of change in List II.
| List I | List II |
| 1. Burning of paper | A: Physical change |
| 2. The ringing of an electric bell | B: Chemical change |
| 3. Curdling of milk | |
| 4. Electric light is switched on | |
| 5. Melting of butter |
What type of energy changes is associated when ice melts?
Give two examples for the following case:
Physical changes which are reversible
If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust.
Do you think rust is different from iron?
Give an example to justify the statement that physical changes can be reversible as well as irreversible.
