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प्रश्न
Compare the energy changes involved during a physical and a chemical change.
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उत्तर
- Physical change: No gain or loss of energy during physical change.
The energy required for completion of a physical change is released when the change is reversed. - Chemical change: Energy is either absorbed or evolved during the chemical change.
The energy in the form of light, percussion (pressure), or generally heat energy is required for 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 short answer.
Name two reversible changes.
Name two reversible changes.
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?
Burning of candle wax, Melting of candle wax, Mixing of iron filings and sand, Burning of wood, Breaking a piece of chalk, Burning a piece of paper, Cutting a piece of paper.
Which of the following are physical changes and which are chemical changes ?
Freezing of water
State what is meant by the term – interconversion of matter. Is interconversion of matter a physical change or a chemical 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.
Natural changes which take place in nature on their own, are beyond the control of human being.
Water is known as a universal solvent. Why?
