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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.
4. Chemical changes involve
- change in shape.
- change in size.
- change in molecular composition.
- none of these
Fill in the blank
Revolution of the earth around the sun is a ________ change.
Tick (√) the correct alternative from the choice given for the following statement
A pop sound is heard when a lighted match stick is brought near the mouth of a jar. This indicates the release of gas.
True or false
Is the process of digestion a physical change?
Which of the following are physical changes ?
- melting of iron metal
- rusting of iron metal
- bending of an iron rod
- drawing a wire of iron metal
Differentiate between a physical change and a chemical change with reference to – Energy change taking place during the respective change.
Select the chemical changes from the following list of changes
Vaporisation of water into water vapour.
Classify the following as physical or chemical properties
Metallic sodium is soft enough to be cut with a knife.
State whether the following statement is true or false:
Stretching of rubber bands is not a physical change.
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 |
