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प्रश्न
Chemical changes are accompanied by changes in energy.
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उत्तर
In a chemical change, molecules and atoms rearrange themselves to form new substances. This rearrangement involves some energy changes. It can either be absorption or evolution of energy.
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संबंधित प्रश्न
True or false?
During a physical change energy is either given out or absorbed by the system.
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.
Under which different types can the following changes be classified?
Revolution of the earth around the sun.
Give reason.
While purchasing canned food, its expiry date should be checked.
Give reason.
A dry handkerchief gets wet at once on dipping in water, but it takes longer for a wet handkerchief to dry.
Picture based question
Observe the picture and list down the changes that are accompanied in the picture.
- ______.
- ______.
- ______.
Observe the picture containing a kettle and note that it has salt water in it and answer the following questions:
- What is name of the process that is done to the kettle?
- What will happen to the content of the kettle?
- What kind of change is occurring on the cold surface of the metal plate?
- What can you say about the quality of water that is obtained in the beaker?
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 |
What is the change?
