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प्रश्न
If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust.
Can you change rust back into iron by some simple method?
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उत्तर
No, rusting is a chemical change and cannot be reversed.
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संबंधित प्रश्न
When carbon dioxide is passed through lime water, it turns milky due to the formation of ______.
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer
Which of the following is a reducing agent?
- oxygen
- chlorine
- hydrogen
- none of these
Define electrolysis.
Give an example of a reaction where the following are involved
Electricity
Distinguish by heating the following in dry test tubs.
Copper Sulphate and copper carbonate
Give reason for the following:
Electrolytic decomposition of water is a reaction involving change of state.
A chemical reaction is often accompanied by external indications or characteristics which include –
- Colour change
- Effervescence or gas evolved
- Evolution or absorption of heat
- Formation of a precipitate.
With reference to each of the above indications, state the external indication seen during – Thermal decomposition of mercury [II] oxide.
NPK are the primary nutrients for plants.
Classify the following processes into physical or chemical changes:
- Beating of aluminium metal to make aluminium foil.
- Digestion of food.
- Cutting of a log of wood into pieces.
- Burning of crackers.
Give two examples for the following case:
Chemical changes
