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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
Explain the following giving an example.
Pure substance
Which of the following are chemical changes?
- Growth of a plant
- Rusting of iron
- Mixing of iron fillings and sand
- Cooking of food
- Digestion of food
- Freezing of water
- Burning of candle
Dissolving salt in water is a reversible change.
Tick the most appropriate answer.
Physical changes are
Classify the following changes as physical or chemical.
Make a list of different types of changes with example.
Match the examples of changes in List I with the correct.
| List I | List II |
| 1. Expansion of a steel rod on heating | A: Physical change |
| 2. Rotting of eggs | B: Chemical change |
| 3. Milk turning sour | |
| 4. Tarnishing of copper | |
| 5. Separation of naphthalene from a mixture of naphthalene and sodium chloride. |
Is a change of state of matter – a physical or a chemical change. Give reasons.
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.
Adding sugar to milk is a physical change.
