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प्रश्न
What are pure substances ? Give two examples of pure substances.
उत्तर
Pure substances are made up of same type of particles or atoms. All the elements and compounds are pure substances because they contain the same kinds of particles.
Examples: Hydrogen, carbon dioxide
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संबंधित प्रश्न
The inter-molecular space is maximum in
Select the correct alternative
The molecules can move freely anywhere in
- gases
- liquids
- solids
- none of the above
What are molecules ?
When a crystal of potassium permanganate is placed at the bottom of water in a beaker, the water in the whole beaker turns purple on its own, even without stirring. This is an example of :
Fill in the following blanks with suitable words :
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Ice, Milk, Iron, Hydrochloric acid, Calcium oxide, Mercury, Brick, Wood, Air
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Silicon, Mercury, Diamond, Sulphur, Iodine, Germanium, Sodium, Carbon, Magnesium, Copper, Boron, Helium
Iron powder and sulphur powder were mixed together and divided into two parts A and B. When part A was heated strongly over a burner, then a substance C was formed. The part B was, however, not heated at all. When dilute hydrochloric acid was added to substance C, then gas D was evolved and when dilute hydrochloric acid was added to part B then gas E was evolved.
- What type of substance is B ?
- What type of substance is C ?
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- State one characteristic property of gas D.
- Write one test to identify gas E.
What happens when the temperature of a saturated sugar solution is increased ?
Fill in the following blank :
A colloid is a ..............mixture and its components can be separated by the technique known as ...............
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Name the process which is used in milk dairies to separate cream from milk.
Fill in the following blanks with suitable words :
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All the matter made of ______.
Complete the following table:
| S.No. | CELSIUS | KELVIN |
| 1. | 90°C | 363 K |
| 2. | ______ | 283 K |
| 3. | 63 °C | ______ |
| 4. | 250°C | ______ |
| 5. | ______ | 303 K |
Evaporation is always accompanied by ______ in temperature.
