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प्रश्न
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
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उत्तर
- Plant growth: Five types of hormones are found in plants, which cause plant growth through chemical processes.
- Rusting of iron: Iron forms undesirable substances when it comes in contact with moisture.
- Cooking of food: Vapors arise while cooking food which is a chemical change.
- Digestion of food: There are chemicals inside our body for digestion.
- Burning of candle: Oxygen is required for this so it is a chemical change.
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संबंधित प्रश्न
Match the columns
| column A | coulmn B |
| 1. A change which cannot be easily reversed | a. man-made change |
| 2.A change that repeats itself at regular intervals | b. chemical change |
| 3. A change that is made by humans | c. physical change |
|
4. A change in which the original substance cannot be obtained |
d. periodic change |
| 5. A change where no new substance is formade | e. irreversible change |
| f. slow change |
Write true or false for the statement
Decomposition of leaves is a fast change.
Ripening of fruits is a desirable change.
Tick (√) the correct alternative from the choice given for the following statement.
A substance which can not sublime is
Solve this crossword by using the clues that follow-
Across
1. Energy in the form of sunlight is absorbed by the green plants in this process.
4. The reddish-brown substance formed over iron in the presence of oxygen and moisture.
5. This change is permanent and irreversible.
6. The process in which a solid directly changes into gaseous state.
Down
1 . It is the change that takes place in case of swinging pendulum of a clock. –
2. Occurrence of this is a non-periodic change as well as a natural change.
3. It is a physical change.
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.
Give the reason why the following is considered as chemical changes.
Copper carbonate on heat gives copper oxide and carbon dioxide.
Name the following.
A form of energy required for a chemical change.
What is the difference between dissolution of sugar and burning of sugar ?
Explain the characteristics of physical change with examples.
