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प्रश्न
Explain the following giving an example.
Pure substance
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उत्तर
- A pure substance is defined as one that contains only one type of atom or molecule.
- A pure substance has the same colour, taste and texture at any given temperature and pressure and a fixed melting and boiling point under continuous pressure.
- Examples include hydrogen gas, salt chloride, and water.
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संबंधित प्रश्न
Classify the following as chemical or physical change:
Cutting of trees
Classify the following as chemical or physical change:
Burning of paper and wood
Fill in the blank.
A new substance is formed in a ............... change.
Write true or false for the statement.
Burning of paper and formation of curd are reversible changes
What role does energy play in initiating a chemical change ?
State whether the following is physical or chemical changes.
water cycle in nature —
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
Classify the following as a physical or a chemical change.
Butter getting rancid
Give the reason why the following is considered as chemical changes.
A bright light is seen evolved when a strip of magnesium is heated.
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 |
