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प्रश्न
What is meant by a substance?
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उत्तर
A substance is a kind of matter that is made up of only one type of particle (either atoms or molecules). It has a definite composition and distinct properties. A substance may be an element (e.g., oxygen, iron) or a compound (e.g., water, carbon dioxide). For example, water is a pure substance because it contains only one type of molecule, H₂O.
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संबंधित प्रश्न
Select homogeneous and heterogeneous mixtures from the following:
The salt solution, petrol, and water, sand, and charcoal, alcohol and water, air dissolved in water, air, seawater, fruit juices, mist, brass.
Give reason:
Why sulphur does dissolve when carbon disulphide is added to a mixture of iron and sulphur but not when it is added to iron sulphide?
Give two examples of the following type of mixture.
gas-gas
Write “true” or “false” for the following statement
A pure substance consists of only one kind of atom or molecule.
Write “true” or “false” for the following statement
Air can be separated from water by filtration.
Give reasons for the following:
Naphthalene and camphor cannot be separated by sublimation.
Among the following______ is a mixture.
Which of the following are physical changes?
(i) Melting of iron metal
(ii) Rusting of iron
(iii) Bending of an iron rod
(iv) Drawing a wire of iron metal
What would you observe when
a mixture of iron filings and sulphur powder is heated strongly
You are given two samples of water labelled as ‘A’ and ‘B’. Sample ‘A’ boils at 100°C and sample ‘B’ boils at 102°C. Which sample of the water will not freeze at 0°C? Comment.
