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प्रश्न
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.
उत्तर
Physical change
- There is no change in the specific properties of the constituents.
Example: The particles of iron can be separated from sulphur with the help of a magnet or by dissolving sulphur in carbon disulphide. - No new substance is formed.
Example: The mixture of iron and sulphur does not form any new substance. - There is no net release or absorption of energy.
Example: When iron and sulphur particles are mixed, heat energy is neither given out nor absorbed. - It is a temporary change and can be reversed by removing the cause of the change.
Example: The particles of iron can be separated from the mixture with the help of a magnet. removing the cause of change.
Chemical change
- There is a specific change in the properties of the constituents.
Example: The particles of iron or sulphur cannot be separated by a magnet or carbon disulphide. - A new substance is formed.
Example: Iron sulphide is the new substance formed when iron and sulphur are heated. - There is a net release or absorption of energy when a chemical change takes place.
Example: When iron sulphide is formed, the test tube gets red hot on account of the release of a large amount of heat energy. - It is a permanent change and cannot be reversed by removing the cause of the change.
Example: The particles of iron can be separated from the mixture with the help of a magnet. removing the cause of change.
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