STD-5, CHAPTER-8: PROPERTIES OF WATER, EXTRA QUESTION ANSWERS

1.      When is a substance said to be dissolved in water?

Ans: When a substance completely mixes in water, such that its particles aew no visible, it is said to have got dissolved in water.

2.      Define a soluble substance.

Ans: A substance which dissolves in water is said to be soluble in it.

3.      Name some substances which are soluble in water.

Ans: Sugar, salt and lemon juice are all soluble in water.

4.      Define a solution.

Ans: When a substance dissolves completely in any medium, we get a solution.

5.      Define a solute.

Ans: The substance, that gets dissolved in a medium to form a solution, is called a solute.

6.      What is a solvent?

Ans: The medium, in which the substance is dissolved, is called a solvent.

7.      Identify the solute and solvent in a nimboo-pani drink.

Ans: In a nimboo-pani drink, Water is the solvent whereas sugar, salt and lemon juice are all solutes.

8.      Define insoluble substances.

Ans: The substances that do not get dissolved in water are said to be insoluble substances (in water).

9.      Name two substances that are insoluble in water.

Ans: Pebbles, saw dust, chalk powder etc. are insoluble in water.

10.  Name two liquids which are soluble in water.

Ans: Lemon juice and vinegar are soluble in water.

11.  Name two liquids which are insoluble in water.

Ans: Kerosene and vegetable oils

12.  Name the liquids which forms a layer above water.

Ans: Kerosene, vegetable oils, hair oils etc. form a layer above water.

13.  Name the liquid which forms a layer below water.

Ans: Carbon tetrachloride forms a layer below water.

14.  Name two gases which are soluble in water.

Ans: Carbon dioxide and oxygen

15.  Name one gas which is not soluble in water.

Ans: Nitrogen

16.  The materials, which do not dissolve in water, either ______ on its surface or _____ to the bottom of the container.

Ans:  The materials, which do not dissolve in water, either float on its surface or sink to the bottom of the container.

17.  Name some solids which sink in water.

Ans: Sand, coins, pebbles, carbon tetra chloride, iron nails, marbles etc. sink in water.

18.  Name some solids which float on water.

Ans: Cork, Butter paper, thermocole, saw dust, float on water.

19.  Name two liquids which float on water.

Ans: Hair oil, mustard oil, float on water.

20.  Name one liquid which sinks in water.

Ans: Carbon tetrachloride

21.  Name the three forms of water.

Ans: Water exists in liquid, solid and vapour form.

22.  How can we change one form of water into another?

Ans: By changing temperature

23.  What do we understand by the terms ‘evaporation’ and ‘condensation’?

Ans: i) Change of a liquid into its vapour form is called Evaporation.

ii) Change of vapour form of a substance into its liquid form, on cooling, is called condensation.

24.  Define water cycle.

Ans: The cyclic process, of evaporation of water from the earth’s surface, followed by its condensation, is called water cycle in nature.

25.  How does rain water get impure?

Ans: By the time, rain water reach the surface of the earth, they become impure, because they dissolve many harmful gases present in air and also get dust and smoke mixed up with them.

26.  Define transpiration.

Ans: Transpiration is the loss of water from parts of plants, especially leaves.

27.  How transpiration plays a key role in cloud formation?

Ans: Transpiration adds to the amount of water vapour present in the air. Thus, it plays a role in cloud formation.