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प्रश्न
What are the characteristic properties of a pure substance? Why do we need them?
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उत्तर
Pure substance : Pure substances have a definite set of properties such as boiling point, melting point, density, etc. They are all homogeneous i.e., their composition is uniform throughout the bulk. Both elements and compounds are pure substances.
Pure substances are needed to :
- Manufacture medicines.
- To prepare chemicals in industry.
- For scientific purposes.
- To maintain the good health of human beings.
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संबंधित प्रश्न
Classify each of the following as a homogeneous or heterogeneous mixture.
Soda water, wood, air, soil, vinegar, filtered tea.
Tick (√) the correct alternative from the choice given for the following statement:
A mixture of mustard oil and water forms
Give an example of mixtures of elements and compounds.
State the technique involved in separating the following:
Iodine crystals and potassium chloride
State whether the following statement is true or false. If false write – the correct statement.
Components in a mixture are present in a definite proportion.
Four atoms of hydrogen combine with one atom of carbon to give methane [CH4]. State the valency of carbon.
Why do we need to separate different components of a mixture? Give two examples.
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
Suggest separation technique(s) one would need to employ to separate the following mixture.
Common salt, water and sand
Supernatant denotes the heterogeneous mixture, lying above a solid residue, after crystallization, precipitation, centrifugation, or another process.
