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प्रश्न
Change is the law of nature and occurs in our everyday life, at all times and in all places. Differentiate between the following change with a suitable example.
Desirable and undesirable change.
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उत्तर
| Desirable change | Undesirable change |
| (i) Changes brought about by nature or man which produces – useful or good results. | (i) Changes brought about by nature or man which produces – useless or bad results. |
| (ii) Positive and advantageous nature. | (ii) Negative and detrimental nature. |
| (iii) Examples of a desirable change: Rain bringing water to the crops, change of milk to curd, ripening of fruits seedling into a plant. |
(iii) Examples of an undesirable change: Rain causing destruction by floods, milk turning sour on a hot day, rotting of fruits, cutting of trees. |
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संबंधित प्रश्न
A burning candle shows both physical and chemical changes. Explain ?
Photosynthesis cannot take place at night.
State one instance where water undergoes a physical change and one in which it undergoes a chemical change.
State what is meant by the term – interconversion of matter. Is interconversion of matter a physical change or a chemical change.
Select the correct answer from the choice given below to complete the sentence
The dissolution of lead nitrate in water is deemed as a _________ change.
Distinguish physical and chemical changes.
Higher order Thinking question
Boiling of water is a physical change; but boiling of egg is a chemical change. Why?
Match the items of Column I with the items of Column II.
| Column I | Column II | ||
| (a) | Large crystals | (i) | Turns lime water into milky |
| (b) | Depositing a layer of zinc on iron | (ii) | Physical change |
| (c) | Souring of milk | (iii) | Rust |
| (d) | Carbon dioxide | (iv) | Sugar candy (Mishri) |
| (e) | Iron oxide | (v) | Chemical change |
| (f) | Dissolving common salt in water | (vi) | Galvanisation |
The change of state of a substance from solid to liquid and liquid to gas is ______.
Mention some of the different conditions needed for chemical changes to occur.
