WBBSE Class 8 Science Solutions Chapter 2.1 Nature of Matter

Detailed explanations in West Bengal Board Class 8 Science Book Solutions Chapter 2.1 Nature of Matter offer valuable context and analysis.

WBBSE Class 8 Science Chapter 2.1 Question Answer – Nature of Matter

Multiple Choice Questions & Answers : (1 mark for each question)

Question 1.
Lightest metal-
i) lithium
ii) hydrogen
iii) sodium
iv) calcium
Answer:
i) Lithium

Question 2.
An electro-positive non-metal is-
i) hydrogen
ii) sodium
iii) graphite
iv) diamond
Answer:
i) Hydrogen

Question 3.
Which of the following liquids has less boiling point?
i) water
ii) alcohol
iii) ether
iv) chloroform
Answer:
iii) ether

Question 4.
Which of these elements has highest density?
i) iron
ii) copper
iii) mercury
iv) gold
Answer:
iii) mercury

Question 5.
Which of the following gas is colourless-
i) nitrogen dioxide
ii) hydrogen
iii) hydrogen sulphide
iv) chlorine
Answer:
ii) hydrogen

Question 6.
Which of the following is magnetic element?
i) copper
ii) gold
iii) diamond
iv) cobalt
Answer:
iv) cobalt

Question 7.
Which of the following is crystalline substance-
i) sugar
ii) blue vitriol
iii) camphor
iv) diamond
Answer:
iii) camphor

Question 8.
Which of the following is conductor of electricity?
i) diamond
ii) sulphur
iii) arsenic
iv) gas carbon
Answer:
iv) gas carbon

Question 9.
Which of the following elements does not produce hydrogen gas by reaction?
i) iron
ii) calcium
iii) zink
iv) copper
Answer:
iv) copper

Question 10.
Which of the following is not metaloid?
i) Arsenic
ii) Antimony
iii) Sulphur
iv) Bismath
Answer:
iii) Sulphur

Question 11.
Sulphur is dissolved in-
i) chloroform
ii) carbon dioxide
iii) water
iv) mercury
Answer:
ii) carbon dioxide

Question 12.
Which of the following has lowest freezing point-
i) water
ii) mercury
iii) both of them
iv) it cannot be said
Answer:
ii) mercury

Question 13.
Which of the metal is most reactive-
i) Magnesium
ii) Sodium
iii) iron
iv) copper
Answer:
iv) copper

Question 14.
Which of the following is physical change-
i) rust on iron
ii) electrolysis of water
iii) melting of ice
iv) burning of paper
Answer:
iii) melting of ice

Question 15.
Which of the following is chemical change-
i) melting of iceberg
ii) boiling of water
iii) pouring of water on lime stone
iv) none of the above
Answer:
iii) pouring of water on lime stone

Question 16.
Powder of chalk and powder of sugar can be separated by-
i) physical property
ii) solubility in water
iii) by magnet
iv) by smelling
Answer:
ii) solubility in water

Question 17.
Which of the following is not a metal?
i) sulphur
ii) diamond
iii) graphite
iv) all of the above
Answer:
iv) all of the above

Question 18.
Which of the following is not soluble in water?
i) sugar
ii) salt
iii) chalk powder
iv) sugar-candy
Answer:
iii) chalk powder

Question 19.
A hard non-metal is-
i) graphite
ii) iodine
iii) diamond
iv) all of the above
Answer:
iv) all of the above

Question 20.
Which of the following is used in photography film?
i) sodium
ii) silver
iii) carbon
iv) hydrogen
Answer:
ii) silver

State whether True or False : (1 mark for each question)

1) Napthaline does not have liquid state.
2) Temperature changes when a liquid boils.
3) SO₂ has a smell like burnt out gunpowder.
4) Iron is a light metal.
5) Sulphur is soluble in carbon tetrachloride.
6) Alcohol mix in water.
7) Br₂ is colourless.
8) Blue vitriol is a crystalline substance.
9) Silver is a non-magnetic substance.
10) Water is an organic solvent.
11) Smell of Ammonium is like burnt out gun power.
12) Metals are fexible.
13) Rusting is a physical change.
14) All metals does not react with acids and produce H₂ gas.
15) Mercury is hard substance, so it is a metal.
16) Though mercury is liquid, it is a metal.
17) Graphite is a bad-conductor as it a non-metal.
18) Cystalline iodine is a non-bright substance.
Answer:
1) true
2) false
3) true
4) false
5) true
6) true
7) false
8) true
9) true
10) false
11) false
12) true
13) false
14) true
15) fale
16) true
17) false
18) false

Fill in the blanks : (1 mark for each question)

1) We can ______ substances by touching.
2) Nitrogen dioxide is ______ in colour.
3) Some substances undergo chemical changes on heating and are _________ into new substances.
4) Water is a _________ substance.
5) Melting point of ice is ________.
6) ______ is a volatile substance.
7) If pieces of zinc is immersed in dilute sulphuric acid _________ gas is produced.
8) ______ metal is used to make cooking utensils.
9) presence of __________ metalloid pollutes water.
10) In nature ____________ element is present in large amount.
11) _____ powder is used in making matchstick.
12) Reaction of iron and CuSO₄ produces Ferrous Sulphate and _____.
13) Bismath is a ______.
14) _______ is used in making electric wire.
15) Put appropriate symbol in following blanks :
i) Ca + H₂ O → Ca(OH)₂ + Ca ______
ii) Fe + H₂ O → FeO₃ + ______
iii) Zn + ______ → ZnSO₄ + H₂
Answer:
1) identify
2) brown
3) transformed
4) liquid
5) 0° C
6 ) ammonium chloride
7) Hydrogen
8) Aluminium
9) Arsenic
10) Oxygen
11) Phosphorus
12) Copper,
13) metalloid,
14) Copper
15) i) H₂
ii) H₂
iii) H₂ SO₄

Match the following : (1 mark for each question)

a) Match the column A with column B.

Column A	Column B
a) Smell of a substance is	i) red
b) Chemical reaction	ii) non-metal
c) Ammonium chloride is a	iii) metal
d) In fixed pressure boiling point is	iv) it is good conductor of heat and electricity
e) Smell of SO2 gas is like	v) a physical property
f) Colour of Bromine is	vi) Hydrogen gas
g) Graphite is a	vii) a definite temperature
h) Gold is a	viii) changes atonic structure of a substance
i) Though graphite	ix) burnt gun power
j) Reaction of metal and acid produces	x) valatile substance.

Answer:
a) Sinell of a substance is a physical property.
b) Chemical reaction changes atomic structure of a substance.
c) Ammonium chloride is a volatile substance.
d) In fixed pressure boiling point is a definite temperature.
e) Smell of SO₂ gas is like burnt gun powder.
f) Colour of Bromine is red.
g) Graphite is a non-metal.
h) Gold is a metal.
i) Though graphite is a non-metal but it is good conductor of heat and electricity.
j) Reaction of metal and acid produces Hydrogen gas.

b) Match the column A with column B.

Column A	Column B
a) In physical change	i) is not soluble in kerosene
b) During the change of state	ii) blue
c) Ether is a	iii) is brown
d) Hydrogen	iv) is a magnetic substance
e) Sugar	v) light yellow coloured hard substance
f) Colour of blue vitriol is	vi) greenish yellow coloured gas
g) Nickel	vii) only outer structure change
h) Colour of NO2 gas	viii) is a odourless gas
i) Sulphur is	ix) temperature does not change.
j) Chlorine is a	x) volatile substance

Answer:
a) In Physical change only outer structure change.
b) During the change of state, temperature does not change.
c) Ether is a volatile substance.
d) Hydrogen is a odourless gas.
e) Sugar is not soluble in kerosene:
f) Colour of blue vitriol is blue.
g) Nickel is a magnetic substance.
h) Colour of NO₂ gas is brown.
i) Sulphur is light yellow coloured hard substance.
j) Chlorine is a greenish yellow coloured gas.

Very Short Questions & Answers : (1 mark for each question)

Question 1.
What is the sign of gold?
Answer:
Sign of gold is Au.

Question 2.
What is the colour of chlorine gas?
Answer:
Greenish yellow is the colour of chlorine gas.

Question 3.
What is the boiling point of :thyl alcohol?
Answer:
Boiling point of ethyl alcohol is 78° C.

Question 4.
Give an example of physical property.
Answer:
smell is an example of physical property.

Question 5.
Give an example of chemical property.
Answer:
Reaction with acid is an example of chemical property.

Question 6.
Give an example of odourless liquid.
Answer:
Water is oderiess liquid.

Question 7.
What is smell of ammonium gas?
Answer:
Smell of ammonium gas is pungent.

Question 8.
Write the symbol of hydrochloric acid.
Answer:
Symbl of hydrochloric acid is HCl.

Question 9.
Write the symbol of zinc sulphate.
Answer:
Symbol of zink sulphateZnSO₄.

Question 10.
Write the symbel of marbel stone.
Answer:
S₂ mbol of marbel stone – CaCO₃.

Question 11.
Give an examples of two magnetic elements.
Answer:
Two magnetic elements Iron and Nickel

Question 12.
Name two crystalline elements.
Answer:
Two crystalline elements Sugar, Sodium Chloride.

Question 13.
Name two non-crystalline elements.
Answer:
Two non-crystalline elements Wax, Camphor.

Question 14.
What type of smell has H₂ S ?
Answer:
Like rotten egg.

Question 15.
Write two names of organic solvent.
Answer:
Two organic solvents Carbondi sulphide, Chloroform.

Question 16.
What is the colour of Nitrogen dioxide?
Answer:
Colour of Nitrogen dioxide Brown.

Question 17.
What will happen if water is powred on quick lime?
Answer:
Quick lime will form with excessive heat.

Question 18.
Write name of two metals which reacts with acid.
Answer:
Sodium and Magnesium reacts with acid.

Question 19.
Write a name of liquid metal.
Answer:
Mercury is liquid metal.

Question 20.
Write a name of liquid non-metal.
Answer:
Bromine is liquid non-metal.

Question 21.
Write name of two metals which have low melting point.
Answer:
Gallium and calsium.

Question 22.
Write a name of light metal.
Answer:
Aluminium.

Question 23.
What is the lightest element?
Answer:
Hydrogen.

Question 24.
Write name of two inactive elements.
Answer:
Helium, Neon are two inactive slements.

Question 25.
Which gas is present in large quantity in atmosphere?
Answer:
Nitrogen.

Question 26.
What elements are present in water?
Answer:
Hydrogen and oxygen.

Question 27.
Which metal is the highest conductor of electricity?
Answer:
Silver is the highest conductor of electricity.

Question 28.
Which ions control the functioning of heart?
Answer:
Ca²⁺ and k⁺.

Question 29.
Write the name of element which is the main constituent of teeth and bones?
Answer:
Calcium.

Question 30.
What is mainly present in haemoglobin?
Answer:
Iron is mainly present in haemoglobin.

Question 31.
Write a name of metal iron which control the constraction of muscle.
Answer:
Mg²⁺.

Question 32.
Which ion plays an important function in the process of coagulation of blood.
Answer:
Calcium ion (Ca²⁺).

Question 33.
What are the two principal cations of our intracellular and extracellular body fluids?
Answer:
Na⁺and K⁺.

Question 34.
Name two proteins which play a vital role in muscle contraction.
Answer:
Actin and myosin play a vital role in muscle contraction.

Question 35.
Write an use of lead.
Answer:
Lead is used in making of battery.

Question 36.
What is the colour of red litmus.
Answer:
The colour of red litmus is red.

Question 37.
What is the colour of red litmus in base?
Answer:
Blue is the colour of red litmus in base.

Question 38.
Name the metals and non-metals present in toothpaste.
Answer:
Carbon, Hydrogen, Oxygen, Aluminium, Calcium.

Short Questions & Answers : (2 marks for each question)

Question 1.
What is matter?
Answer:
All the materials in our surrounding are composed of matter. Matter has mass and volume which can be felt by our senses.

Question 2.
What are physical properties?
Answer:
Some properties of a substance, such as physical state, colour, odour, melting point, boiling point, magnetism, solubility etc. from which we can get an idea about the nature and external condition of the substance, are called the physical properties of substance.

Question 3.
What are chemical properties?
Answer:
The properties of a substance which decide its tendency and power to react with other substances are called its chemical properties.

Question 4.
Give example of chemical properties.
Answer:
On electrolysis, water gives hydrogen and oxygen. This is a chemical property of water. Zinc reacts with dilute sulphuric acid to produce hydrogen gas. This is a chemical property of zinc.

Question 5.
Water can exist in three states. What are they?
Answer :
Water can exist in three states. They are solid state : ice, liquid state : water, Gaseous state : water vapour.

Question 6.
Write name of some gas which have odour, mention how they smell.
Answer:
Ammonia → pungent-smelling. Hydrogen sulphide → rotten egg. Sulphurdi oxide → burnt gunpowder. Phosphin → rotten fish.

Question 7.
Write name of some colourful gas, write their colours.
Answer:
Nitrogen dioxide → brown. Chlorine → Greenish yellow. Iodine vapour → violet.

Question 8.
How could you seperate sugar powder and burnt out lime powder from its physical properties?
Answer:
Sugar powder makes a clear solution when mixed with water, but burnt out lime does not melt in water, it floats on water.

Question 9.
How could you seperate sugar powder from salt powder by to chemical properties?
Answer:
We could seperate them by giving heat. When heated sugar powder becomes brown first and then it becomes black. Whereas salt powder would not have any remarkable change when heated up.

Question 10.
What reaction will happen if dilute H₂ SO₄ is added to zinc powder?
Answer:
If dilute H₂ SO₄ is added to zinc powder it reacts and produces zinc sulphate salt and gas bubbles of hydrogen. Zn + H₂ SO₄ = ZnSO₄ + H₂

Question 11.
What would happen if water is poured on calcium oxide?
Answer:
If water is poured on calcium oxide a reaction will occur which would produce lot of heat and slaked lime will be produced.
CaO+H₂ O=Ca(OH)₂ + heat.

Question 12.
What is metalloid? Give example.
Answer:
Metailoids are chemical elements inter-mediate in properties between metals and nonmetals. Example: Arsenic, Antimone, Bismath.

Question 13.
What are magnetic elements? Give ex:mple.
Answer:
The substances which are attracted by magnet are called magnetic elements. For example : iron, nicel, cobalt.

Question 14.
What are metals?
Answer:
Metals are defined as elements that form positive ions by losing electrons. They contain 1-3 valence electrons. For example-sodium has 1 . copper has 2 and aluminium has 3 valence electrons.

Question 15.
What are non-metals?
Answer:
Non-metals are defined as clements that form negative ions by gaining electrons. They contain 4-7 valence electrons. For example, carbon has 4, nitrogen has 5, oxygen has 6 and chlorine has 7 valence electrons.

Long Questions & Answers : (3 marks for each question)

Question 1.
What would happen if magnesium wire is burnt in air?
Answer:
If magnesium wire is burnt in air it would burn with bright flame. Magnesium reacts with oxygen upon ignition and then continues to burn with a bright flame forming white powder of magnesium oxide. Magnesium will react with nitrogen and form magnesium nitrate.

2 Mg+O₂ = 2 MgO
3 Mg+N₂ = Mg₃ N₂

Question 2.
Though hydrogen is a gas it is placed in activity series why?
Answer:
Though hydrogen is a non-metal it is placed in the activity series as it forms positively charged ions by losing electrons. In general it is found that:-
A metal higher up than hydrogen in the activity series can displace hydrogen from dilute acids or water. A metal lower down than hydrogen cannot displace it. Again a metal on the left hand side of hyudrogen will displace another metal on its right from the salt of the latter metal.

Question 3.
Write some uses of Graphite.
Answer:

1. As electrodes in batteries.
2. as the core of ‘bad’ pencils.
3. as a lubrcant in fast-moving machinery
4. in making heat resistant crucibles, that can with stand high temperatures and are used to melt small quantities of metals.

Question 4.
It is possible to keep CuSO₄ solution in an iron dish?
Answer:
No it is not possible to keep CuSO₄ solution in an iron dish as reactivity of iron is mere than copper. Iron will displace copper from CuSO₄ and form FeSO₄.
Fe + CuSO₄ → FeSO₄ + Cu.

Question 5.
Give some examples :
i) Two high electro-positive metal.
ii) Two low electro-positive metal.
iii) Two medium electro-positive metal.
Answer :
i) Two high electro-positive metals → Sodium, Potassium.
ii) Two low electro-positive metals → Copper, Silver.
iii) Two medium electro-positive metal → Zinc, Lead.

Question 6.
Discuss how certain elements help in formation of some important compounds in human body .
Answer:
Several compounds likephospholipid, nucleic acid, metalloprotein, amino acid etr.play vital roles in the formation of organelles, cell and tissues of the human body. The non-metals like C, H, O, N, P, S and metals like Fe, Cu Se, Mn are also involved in the formation of these compounds.

Question 7.
Discuss how certain elements jicrform maintenance of water balance, functioning of the heart, acid-base equilibrium in our body.
Answer:
Certain important functions are-
1. Maintenance of water balance in Human Body: Na⁺and K⁺are two principal cations of our intracellular and extracellular body fluids.
2. Functioning of the Heart: Concentration of Ca²⁺ and K^–controls the excitability and 1ythmic contraction expansion of the human heart.
3. Acid-Base Equilibrium: Acid-Base equilibrium is controled by K⁺. If the acid-base balance is lost, erosion of bone joints initiates (arthritis) and bone density gets lowered (osteoporosis).

Question 8.
Discuss how certain elements perform maintenance of formation of teeth and bone, functioning of enzymes, coagulation of Blood in our body.
Answer:
Certain important functions are-
i) Formation of teeth and bone: Calcium, Magnesium and Phosphorus are responsible for the mechanical strength of our teeth and bones.
ii) Functioning of Enzymes: Several metallic and non-metallic ions like Ca²⁺, Mg²⁺, Mn²⁺, Na⁺, Zn²⁺, Cl^–, Fe²⁺, Fe³+, Cu²⁺, PO₄^3- are use for the function of enzymes in the human body.
iii) Coagulation of Blood: Calcium ion (Ca²⁺) plays a very important function in activating different factors that participate in the process of coagulation.

Question 9.
Discuss how certain elements perform Constraction of muscle and conduction of nerve impulse, Transport, Storage and Utilization of Oxygen, formation of hormone in our body.
Answer:
Certain important functions are-
i) Constraction of muscle and conduction of nerve impulse : Ca²⁺, Mg²⁺, Na⁺and K⁺ control the excitability of muscles.
ii) Transport, Storage and Utilization of Oxygen: Haemoglobin in blood transports oxygen. Myoglobin in muscles stores oxygen. Iron is one of the indispensable components of these two proteins.
iii) Formation of Hormone: Zinc ion plays a significant role in the storage and stabilization of insulin hormone secreted from the pancreatic glands associated with the alimentary canal.

Question 10.
Name the metals and non-metals present in the compounds we use in our day to day life?
(i) Tooth paste
(ii) Gun powder of match stick
(iii) Chemical Fertiliser
(v) Stainless steel
(vi) Cement
(vii) Photographic film.
Answer:

i) Tooth paste	Carbon, Hydrogen, Oxygen, Aluminium, Calcium.
ii) Gunpowder of match stick	Red phosphorus, Chlorine. Oxygen, potassium.
iii) Plant and animal food	Carbon, Oxygen, Hydrogen. Nitrogen, S, P, Na, Ca, Mg, Fe, K
iv) Chemical Fertíliser	Nitrogen, Phosphorus, Potassium.
v) Stainless steel	Iron, Chromium, Carbon.
vi) Cement	Aluminium, Silicon, Oxygen.
vii) Photographic film	Silver, Carbon, Hydrogen, Oxygen.

Question 11.
Name the metals and non-metals present in the compounds we use in our day to day life?
Answer:

Metal	Non-metals
i. Metals are solids at room temperature, except mercury, which is liquid at room temperature.	i. Non-metals are gases or solids at room temperature, except bromine, which is liquid at room temperature.
ii. They are generally hard and strong, except sodium and potassium.	ii. Non-metal solids are generally not as hard as metals, however diamond is very hard.
iii. They have metallic lustre (shine).	iii. They do not have lustre, exception silicon and graphite have metallic lustre.
iv. They have high melting and boiling points exceptions are sodium, potassium, mercury and gallium.	iv. They have low melting and boiling points, exception graphite has high melting and boiling point
v. They are good conductors of heat and electricity.	v. They are bad conductors of heat and electricity, exception is graphite.
vi. They can be beaten into thin sheets and foils, exceptions are sodium and potassium.	vi. Non-meta!s can neither be beaten into thin sheets nor can be drawn into wires.
vii. Most metals have high tensile strength.	vii. They have low tensile strengths.
viii. They can be draw into wire, exceptions are sodium and potassium.	viii. They usually have low densities.