Very Short Answer Questions - 1 Mark

Q. 1. How can you change a saturated solution to an unsaturated solution without adding any more solved to it?

Ans. By heating the saturated solution, it becomes unsaturated.

Q. 2. Sucrose (sugar) crystals obtained from sugarcane and beetroot are mixed together. Will it be a pure substance or a mixture? Give reasons for the same.

Ans. It is a pure substance because chemical composition of sugar crystals is same irrespective of its source.

Q.3. Based on which factor a solution is said to be diluted, concentrated or saturated?

Ans. solution is said to be diluted, concentrated or saturated on the basis of the amount of solute dissolved in the solution.

Q. 4. Identify solute and solvent in 'tincture of iodine'.

Ans. Iodine is the solute and alcohol is the solvent.

Q. 5. What is mass per cent of a solution?

Ans. It is defined as the mass in grams of the solute present in one hundred grams of a solution.

Q. 6. What are the two components of a colloidal solution?

Ans. The two components of a colloidal solution are dispersed phase and dispersing medium.

Q. 7. In what respect does a true solution differ from a colloidal solution?

Ans. A true solution is homogeneous whereas a colloidal solution is heterogeneous.

Q. 8. Two liquids 'A' and B' are miscible with each other at room temperature. Which separation technique will you apply to separate the mixture of A' and "B' if the difference in their boiling points is 27°C?

Ans. We can separate miscible liquids by fractional distillation, if both the liquids have difference in their boiling points, So, the mixture of liquids 'A' and 'B' can be separated by fractional distillation.

Q. 9. Define crystallisation.

Ans. It is a process that separates a pure solid in the form of its crystals from a solution.

Q. 10. Why is crystallisation technique considered better than simple evaporation to purify solids?

Ans. Crystallisation is considered better than simple evaporation because

(i) some solids decompose or get charred on heating to dryness.
(ii) some impurities may remain dissolved in the solution even after filtration. On evaporation, these contaminate the solid.

Q. 11. Why is water called universal solvent?

Ans. Water is known as universal solvent because it has the ability to dissolve wide variety of substance.

Q. 12. Which of the following are physical changes?

Melting of iron metal, rusting of iron, bending of iron rod, drawing a wire of iron metal.

Ans. Melting of iron metal, bending of iron rod and drawing a wire of iron metal are physical changes because there is no change in the chemical composition of iron, only its form is changing.

Q. 13. Name two elements which exist in liquid state at room temperature.

Ans. Gallium and mercury exist in liquid state at room temperature.

Q. 14. An unknown substance A' on thermal decomposition produces 'B' and C'. What is 'A'-an element, a compound or a mixture?

Ans. Unknown substance A' should be a compound because elements and mixture do not decompose.

Q. 15. Identify the elements from the following substances: sulphur, brine, hydrochloric acid, water, neon, paper, sugar.

Ans. The elements are sulphur and neon.