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प्रश्न
State the observations seen, when milk in a dish is kept aside for a few hours or more. Is the change which occurs – a physical change or a chemical change. Give reasons.
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उत्तर
On keeping aside – the milk in a dish for a few hours or more. The change observed – will be that the milk has changed into curd. The change is permanent and cannot be reversed. New substance curd is formed. It is a chemical change.
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संबंधित प्रश्न
Tick the most appropriate answer
2. Melting of ice is a
- reversible change
- irreversible change
- chemical change
- none of these
Fill in the blank.
Heat is .................... by a gas during the process of condensation.
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
Define physical change. Give two examples for the above changes.
True or false
Is the process of digestion a physical change?
Write true or false
Deforestation is a man-made change.
Two chemical substances X and Y combine together to form a product P which contains both X and Y X + Y P
X and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following statements concerning X, Y and P are correct ?
- P is a compound
- X and Y are compounds
- X and Y are elements
- P has a fixed composition
Which of the following are physical changes and which are chemical changes ?
Name the following:
The final product of the physical change involved during the ‘melting of a piece of wax’.
When a woolen yarn is knitted to get a sweater, the change can be classified as ____________.
