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प्रश्न
Give a reason why – Heating a platinum wire is a reversible change but, heating a magnesium wire is an irreversible change.
उत्तर
Heating a platinum wire, the final product is again platinum wire (as platinum is a noble metal and does not react with air), i.e. no change in composition and is a physical change. Heating magnesium wire forms MgO i.e. composition changes a new substance white powder of magnesium oxide is formed is a chemical change.
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संबंधित प्रश्न
Match the columns
| column A | coulmn B |
| 1. A change which cannot be easily reversed | a. man-made change |
| 2.A change that repeats itself at regular intervals | b. chemical change |
| 3. A change that is made by humans | c. physical change |
|
4. A change in which the original substance cannot be obtained |
d. periodic change |
| 5. A change where no new substance is formade | e. irreversible change |
| f. slow change |
Ripening of fruits is a desirable change.
Write short answer.
Sublimation is classified as a physical change. Why ?
State whether the following is physical or chemical changes.
respiration in living beings —
Write true or false
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Classify the following as physical or chemical changes :
- Cooking of food
- Boiling of water
- Cutting of trees
- D0issolving salt in water
- Digestion of food
- Melting of ice
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Name the following.
The gaseous product of the chemical change which takes place during respiration in living organisms.
Which of the following is not a physical change?
