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प्रश्न
What role does energy play in initiating a chemical change ?
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उत्तर
In a chemical change molecules and atoms rearrange themselves to form new substances. This process involves some energy changes. In some changes energy is absorbed
e. g. burning of a substance and in some cases energy is evolved e.g. photosynthesis
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संबंधित प्रश्न
Tick (√) the correct alternative from the choice given for the following statement
Burning is a
True or false?
During a physical change energy is either given out or absorbed by the system.
Melting of solid (wax) is a physical change.
Distinguish between the following.
Periodic change and non-periodic change
Under which different types can the following changes be classified?
Conversion of milk into yoghurt.
Give reason.
A dry handkerchief gets wet at once on dipping in water, but it takes longer for a wet handkerchief to dry.
How can a change occur in a substance?
Some changes are listed in the following table. For each change, write in the blank column, whether the change can be reversed or not.
| S. No. | Change | Can be reversed (Yes/No) |
| 1. | The sawing of a piece of wood | |
| 2. | The melting of ice candy | |
| 3. | Dissolving sugar in water | |
| 4. | The cooking of food | |
| 5. | The ripening of a mango | |
| 6. | Souring of milk |
The difference between initial state and the final state is called change.
______ is the process in which something becomes different from what it was earlier.
