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प्रश्न
Distinguish physical and chemical changes.
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उत्तर
1. Physical changes:
- No new substance is formed
- Reversible
- Change in physical properties like size, shape, state
- Melting of ice, tearing of paper freezing, evaporation vaporization
2. Chemical changes:
- New substance is formed
- Irreversible
- Change in properties of reactants and products
- Burning of paper, photosynthesis, digestion of food, rusting of iron
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संबंधित प्रश्न
What role does energy play in initiating a chemical change ?
State whether the following is physical or chemical change.
Digestion of food —
Tick (√) the correct alternative from the choice given for the following statement.
A substance which can not sublime is
Write true or false
Decomposition of leaves is a fast change.
Fill in the blank.
The process of a liquid changing into a solid is called ________
State which of the following terms connected with change of state of matter i.e.
(a) Melting
(b) Vaporisation
(c) Condensation
(d) Freezing
pertain to –
- Conversion of a liquid into a vapour or gas.
- Conversion of a liquid into a solid.
- Conversion of a solid into a liquid on heating.
Potassium chloride is added to water and stirred. A salt solution is obtained, which is then boiled, leaving behind a residue.
- Is the above change physical or chemical?
- Name the residue which remains behind after the salt solution is boiled.
- Is the change reversible or not reversible?
- Are the composition and properties of the original substance altered?
- Give a reason why the above experimentation would not be possible if calcium carbonate was taken in place of potassium chloride.
Give a reason why – Addition of zinc nitrate to water is a physical change but, the addition of zinc to dilute nitric acid is a chemical change.
State which of the following 1 to 5 pertain to – A: Physical Change B: Chemical change :
- Sublimation.
- Fermentation.
- Liquefaction or condensation.
- Magnetization.
- Respiration.
Match the following
| Sr. No. | A | B | C |
| 1. | Melting | Change of state from liquid to solid | Ticking of clock |
| 2. | Condensation | Change of state from liquid to gas | Formation of ice cube |
| 3. | Evaporation | Change of state from solid to liquid | Collecting flowers |
| 4. | Freezing | Change of state from gas to liquid | Ice cube to water |
| 5. | Periodic change | Occurs at irregular time intervals | Water to steam |
| 6. | Non-periodic change | Occurs at regular time intervals | Steam to water drops |
