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प्रश्न
What role does energy play in initiating a chemical change ?
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
State whether the following is physical or chemical changes.
passing electric current through a heater rod —
State whether the following is physical or chemical changes.
Melting of wax —
Tick (√) the correct alternative from the choice given for the following statement
When sugar is heated, its colour changes into
True or false?
During a physical change energy is either given out or absorbed by the system.
Under which different types can the following changes be classified?
Bursting of a cracker.
Fill in the blanks with the appropriate words of the statement given below:
Chemical changes may involve exchange of energy in the form of __________ and _________.
Fill in the blank with the correct word of the statement given below:
Ammonium chloride, a sublimable solid undergoes _________ on heating.
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.
What is the change?
