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प्रश्न
Which of the following are chemical changes ?
- decaying of wood
- burning of wood
- sawing of wood
- hammering of nail into wood
विकल्प
(i) and (ii)
(ii) and (iii)
(iii) and (iv)
(i) and (iv)
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उत्तर
(i) and (ii)
The processes in statements (i) and (ii) are chemical changes because decaying and burning causes formation of new compounds; thus they are chemical reactions. The processes in statements (iii) and (iv) are physical changes where no new compounds are formed.
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संबंधित प्रश्न
Tick the most appropriate answer.
3. Physical changes are
- permanent.
- periodic,
- temporary
- irreversible.
Fill in the blank.
A new substance is formed in a ............... change.
Write short answer.
Give two examples of periodic changes
Tick (√) the correct alternative from the choice given for the following statement.
An example of both physical and chemical change is
Classify the following as a physical or a chemical change.
Boiling of water
Fill in the blank.
The reaction in which energy is evolved is called
Give a reason why
Freezing of water is a reversible change while burning of a candle – an irreversible change.
Give four reasons why the burning of a magnesium ribbon in the air is considered a chemical change.
Is a change of state of matter – a physical or a chemical change. Give reasons.
Classify the following as physical or chemical properties
Metallic sodium is soft enough to be cut with a knife.
