Is Matter Around Us Pure 

Q15. What are the types of pure substances?

Or

How matter is classified in terms of composition?

Ans. On the basis of their chemical composition, substances can be classified either as elements or compounds.

Q16. What are the types of mixtures?

Ans. Mixtures are of two types: homogeneous mixtures and heterogeneous mixtures

Q17. How are elements further classified?

Ans. Elements can be normally divided into metals, non-metals and metalloids.

Q18. Is dye in black ink a single colour? Justify your answer.

Ans. It is not a single colour. Usually, a dye is a mixture of two or more colours. We can separate it by the process of chromatography.

Q19. What is meant by a pure substance?

Ans. A pure substance consists of a single type of particles. Example: hydrogen, oxygen, nitrogen, iron, copper, silver, gold etc.

Q20. What is the principle of separating immiscible liquids using separating funnel?

Ans. The principle is that immiscible liquids separate out in layers depending on their densities. 

Q21. What type of liquid mixture will kerosene oil and water form?

Or

What happens when you mix water and kerosene?

Ans. When two liquids do not mix, they form two separate layers and are known as immiscible liquids.

Q22. Identify the solutions among the following mixtures.

(a) Soil

(b) Sea water

(c) Air

(d) Coal

(e) Soda water. 

Ans. The following are the solutions from the above mentioned list of mixtures: Sea water, Air, Soda water

Q23. What is meant by concentration of a solution?

Ans. The concentration of a solution is the amount of solute present per unit volume or per unit mass of the solution/solvent.

Q24. What is meant by solubility?

Ans. The amount of the solute present in the saturated solution at this temperature is called its solubility.

Q25. Classify each of the following as a homogeneous or heterogeneous mixture. soda water, wood, air, soil, vinegar, filtered tea.

Ans. Homogeneous Mixture: Soda water, vinegar, filtered tea

Heterogeneous Mixture: Wood, air, soil

Q26. Which of the following materials fall in the category of a “pure substance”?

(a) Ice

(b) Milk

(c) Iron

(d) Hydrochloric acid

(e) Calcium oxide

(f) Mercury

(g) Brick

(h) Wood

(i) Air 

Ans. The following materials from the above mentioned list are pure substance: Ice, Iron, Hydrochloric acid, Calcium oxide, Mercury

Q27. Which method is used to obtain copper sulphate from an impure sample?

Ans. Copper sulphate can be obtained from an impure sample by crystallization.

Q28. What is tincture of iodine? Identify the solute and solvent in it.

Ans. A solution of iodine in alcohol known as ‘tincture of iodine’, has iodine (solid) as the solute and alcohol (liquid) as the solvent.

Q29. Define element.

Ans. Element is defined as a basic form of matter that cannot be broken down into simpler substances by chemical reactions.

Q30. What is a mixture?

Ans. Mixtures are constituted by more than one kind of pure form of matter, known as a substance.

Q31. Try segregating the things around you as pure substances or mixtures.

Ans. Pure substance - Water, sugar and gold

Mixtures- steel, plastic, paper, air and milk 

Q32. What is an unsaturated solution?

Ans. If the amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution.

Q33. What do you mean by interconversion of states of matter?

Ans. The phenomenon of change from one state of matter to another, and then back to the original state is called the Interconversion of states of matter.

Q34. Out of colloid, solution and a suspension which one can be separated by filtration.

Ans. The solute particles settle down when a suspension is left undisturbed, that is, a suspension is unstable. They can be separated from the mixture by the process of filtration.

Q35. What are metalloids? Give examples.

Ans. Some elements have intermediate properties between those of metals and non-metals, they are called metalloids; examples are boron, silicon, germanium etc.

Q36. Give an example of a solution in which solid is a solute as well as the solvent.

Ans. Alloy is an example of solution containing a solid solute in a solid solvent. For example, brass is a mixture of approximately 30% zinc and 70% copper.

Q37. Can we separate alcohol dissolved in water by using a separating funnel? If yes, then describe the procedure. If not, explain.

Ans. It is not possible to separate mixture of alcohol and water by using a separating funnel because these are not immiscible liquids. The mixture of alcohol and water can be separated by the process of distillation.

Q38. Name the technique to separate

(i) butter from curd,

(ii) salt from sea-water,

(iii) camphor from salt.

Ans. (i) Centrifugation

(ii) Evaporation

(iii) Sublimation