Kerala SCERT Class 8 Basic Science Chapter 16 Water Question Answer Solution Here. Kerala Board Class 8 Students can find Here 16th Chapter Water Notes provide by our Teacher. Important Question Answer from Chapter 16 Water.
- Board- Kerala Board.
- Class – 8.
- Subject – Basic Science Part 2
- Chapter – 16.
- Chapter Name – Water.
- Topic – Question Answer Solution.
Answer the following in one sentence.
1.) What is water?
Ans- water is the precious natural resources. Water have its melting point, boiling point, freezing point and water is also called the universal solvent.
2.) Define
a.) Boiling point if water-
The temperature at which a liquid boils at normal atmospheric pressure is its boiling point. The boiling point of water is 100 degree Celsius.
b.) Heat capacity of water –
The heat capacity of water is the capacity of water to hold more heat as compared to other substances.
c.) Freezing point of water-
Freezing point of a liquid is the temperature at which it freezes to solid at normal atmospheric pressure. The freezing point of water is 0 degree celcius.
d.) Surface tention-
Surface tention is the reduced in surface area of a liquid. For the spherical liquid drops have minimum surface area.
e.) Soft water-
The water in which soap gives lather readily is called soft water.
f.) Hard water-
The water in which soap does not lather easily is called hard water.
3.) What is temporary hardness of water?
Ans- the hardness of water containg calcium or Magnesium bicarbonates is removed during boiling , this type of hardness of water is known as temporary hardness of water.
4.) Define heavy water and neutral solvent.
Ans- heavy water is water molecules containing deuterium , instead of ordiniary hydrogen atoms. this water is known as heavy water.
Neutral solvent is pure water has nighter the properties of aicd nor those of alkali therefore this water is called neutral solvent.
Answer the following in short.
1.) Why water is called universal solvent. Explain it with proper example.
Ans- water is called as universal solvent becaused water can dissolved various substances and widely used for preparing solutions so it is called as universal solvent.
For example- take beakers and add cloured inks, coloured salts( copper sulphate, nickel sulphate etc) to water in different beaker and miix them well. After that observed the clour change in water. You can see the water can acquire the clour of any coloured substances.
2.) Give difference between hard water and soft water.
Ans-
Hard water |
Soft water |
The water in which soap does not lather easily is called hard water. | The water which soap gives lather readily is called soft water. |
Hard water contains calcium or magnesium bicarbonates. | Soft water do not contain calcium or magnesium bicarbonates. |
There are two types of hardness of water temporary hardness and permanent hardness. | There no further types of soft water. |
3.) What is hardness of water and heavy water.
Ans- the hardness of water is due to the presence of dissoilved salts of calcium and magnesium.
There are two types of water hardness temporary and permenant hardness of water.
A) Temporary hardness of water- the water contain calcium or magneshium bicarbonates is removed during boiling. This type of hardness of water is known as temporary hardness.
B) Pemanent hardness of water- the water containg the chlorides and suphates of calcium and magnesium is not removed even after boiling. This type of hardness of water is called pemanent harndess. Pemanent hardness of water only removed by using certain chemicals.
Heavy water- the water molecules contaiing deuterium, the isotope of hydrogen, instead of ordinary hydrogen atms this is called heavy water and this water is used in nuclear reactions.
4.) Explain surface tension of water.
Ans- the surface tension of water is the is related to the water molecules. The number of molecules in vapour from just above the surfaces of water is less than those on the surface. Therefore the attraction towards the sides and the interior will be greater. Consequently the liquid surfaces behaves like a streached membrane. This behaviour is caused by surface tension. Some things float on water like small insects , blade can flot on water. All this things are possible due to surface tension. Surface tension is charactersitic property of all liquids.
Surface tension acts in such way so as to reduce the surface area of liquid. For the definite mass of a substance, surface area is minimum for spherical that is why liquid droplates assurance spehrical shape.
Answer the following in detail.
1.) Explain in detail about the causes of water pollution.
Ans- water pollution is a large pollution. The harmful or chemical substances which are harmful or dangerous to living organism which release in water body increases the water pollution. Due to water pollution aquatic water do not get fresh air. Due to water pollution environment get more polluted, There are various caused of water pollution like-
A) Dumping of wastes in water resources
B) Rempant use of fertilizers
C) Excessive getting mixed with water
D) Waste water from industries which harmful for aquatic animals
E) Insceticides getting mixed with water
F) Deforestation
G)
2.) Write note on components of water.
Ans- there are some components present in water. As you known that water is formed by the combination of the constituent elemetns , hydrogen and oxygen. Hydrogen and oxygen can be produced by decomposing water and water can be produced by combining hydrogen and oxygen. Water can be decomposed into its components by electrolysis. The volumes of hydrogen and oxygen is 2:1. water molecule contains hydrogen and oxygen atoms in the sa,e ratio hence it is represented as H2O.
3.) Soap decreases the surface tention of water explain it with example.
Ans- soap can decrease the surface tension of water is related to laundry and soap concept. For removing dirt from the fabric , water should move easily through the fine threds of the fabric. It is only possible by decreasing the attractive forces between water molecules. This is done by decreasing the surface tension of water. Soap can decreasing the surface tension of water . therefore washing clothes is easier with soap. Soap molecules can get into the particles of dirt in the fabric , attract water molecules and reduce the surface tension of water. Thus , dirt particles are easily removed from the fabric along with water molecules.
From this we can know that soap decrease the surface tension of water.
MCQ
1) Water is known as—–
a) Precious natural resource
b) Universal solvent
c) Netural
d) All of the above
Ans- d) all of the above
2) The temperature at which a liquid boils at normal atmospheric pressure is called——-
A) Boiling point
B) Freezing point
C) Melting point
D) None of the above
Ans- a) boiling point
3) When water is converted into ice its volume—- and density —–
a) Increase, decrease
b) Decrease, increase
c) Constant
d) No change
Ans- a) increase, decrease
4) The temporary hardness is removing of—— during boiling.
a) Calcium or magnesium bicarbonates
b) Chlorides
c) Sulphates
d) Calcium and magnesium
Ans- a) calcium or magnesium bicarbonates
5) Heavy water containg the ……. of hydrogen
a) Isobar
b) Isotope
c) Both a and b
d) None of the above
Ans- b) isotope
Kerala SCERT Class 8 Science Water Question Answer
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