Author name: Prasanna

These NCERT Solutions for Class 9 Maths Chapter 4 Linear Equations in Two Variables Ex 4.1 Questions and Answers are prepared by our highly skilled subject experts.

NCERT Solutions for Class 9 Maths Chapter 4 Linear Equations in Two Variables Exercise 4.1

Question 1.
The cost of a notebook is twice the cost of a pen. Write a linear equation in two variables to represent this statement.
Solution:
Let the cost of a notebook is Rs. x and the cost of a pen is Rs. y
According to question
x = 2y or, x – 2y = 0
Therefore the linear equation in two variables to represent this statement is x – 2y = 0

Question 2.
Express the following linear equations in the form ax + by + c = 0 and indicate the values of a, b and c in each case:
(i) 2x + 3y = 9.\(\bar{35}\)
(ii) x – \(\frac {y}{5}\) – 10 = 0
(iii) -2x + 3y = 6
(iv) x = 3y
(v) -2x = -5y
(vi) 3x + 2 = 0
(vii) y – 2 = 0
(viii) 5 = 2x
Solution:
(i) We have given that
2x + 3y = 9.\(\bar{35}\)
2x + 3y – 9.\(\bar{35}\) = 0
Now, it is the form of ax + by + c = 0
Therefore the values of a, b and c are 2, 3 and -9.\(\bar{35}\) respectively.

(ii) We have given that
x – \(\frac {y}{5}\) – 10 = 0
We can also write
1x + (\(\frac {-y}{5}\)) y + (-10) = 0
Now, it is in the form of ax + by + c = 0
Therefore values of a, b and c are 1, \(\frac {-y}{5}\), and -10 respectively.

(iii) We have given that
-2x + 3y = 6
or, -2x + 3y – 6 = 0
We can also write
(-2)x + 3y + (-6) = 0
Now, it is in the form of ax + by + c = 0
Therefore, the values of a, b and c are -2, 3 and -6 respectively.

(iv) We have given that,
x = 3y
or, x – 3y = 0
We can also write
1x + (-3)y + 0 = 0
Now, it is in the form of ax + by + c = 0 and the values of a, b and c are 1, -3 and 0 respectively.

(v) We have given that
2x = -5y
or, 2x + 5y = 0
We can also write 2x + 5y + 0 = 0
Now, it is in the form of ax + by + c = 0.
Therefore, the values of a, b and c are 2, 5 and 0 respectively.

(vi) We have given that
3x + 2 = 0
We can also write 3x + 0y + 2 = 0
Now, it is in the form of ax + by + c = 0
Therefore, the values of a, b and c are 3, 0 and 2 respectively.

(vii) y – 2 = 0
We can also write,
0x + 1y + (-2) = 0
Now, it is in the form of ax + by + c = 0.
Therefore, the values of a, b and c are 0, 1 and -2 respectively.

(viii) we have given that
5 = 2x
or, 2x – 5 = 0
We can also write
2x + 0y + (-5) = 0
Now it is in the form of ax + by + c = 0.
Therefore, the values of a, b and c are 2, 0 and (-5) respectively.

These NCERT Solutions for Class 8 Science Chapter 5 Coal and Petroleum Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Coal and Petroleum NCERT Solutions for Class 8 Science Chapter 5

Class 8 Science Chapter 5 Coal and Petroleum Textbook Exercise Questions and Answers

Page 62-63

Question 1.
What are the advantages of using CNG and LPG as fuels?
Answer:
Following are the advantages of using CNG and LPG as fuels:

• CNG and LPG are the cleanest of all the fossil fuels. They do not leave behind any residue on burning.
• Compressed Natural Gas (CNG) and LPG are less polluting and non-corrosive which can be used for burning.
• Calorific value of these fuels is very high. Hence they are used for cooking purposes.

Question 2.
Name the petroleum product used for surfacing of roads.
Answer:
These days bitumen, a petroleum product, is used for surfacing the roads in place of coal tar.

Question 3.
Describe how coal is formed from dead vegetation. What is this process called?
Answer:
Millions of years ago, dense forests and animals got buried under the soil due to natural processes like floods, earthquakes and thunderstorms. When they got buried deep in the soil, they were exposed to very high pressure and temperature. Under these conditions, these slowly got converted into coal. This process of formation of coal is called carbonisation.

Question 4.
Fill in the blanks:
a. Fossil fuels are ………………, ……………… and ………………
b. Process of separation of different constituents from petroleum is called ………………,
c. The least polluting fuel for vehicle is ………………,
Answer:
a. coal, petroleum, natural gas,
b. refining,
c. CNG

Question 5.
Tick True/False against the following statements:
a. Fossil fuels can be made in the laboratory. (T/F)
b. CNG is more polluting fuel than petrol. (T/F)
c. Coke is almost pure form of carbon. (T/F)
d. Coal tar is a mixture of various substances. (T/F)
e. Kerosene is not a fossil fuel. (T/F)
Answer:
(a) False
(b) False
(c) True
(d) True
(e) False

Question 6.
Explain why fossil fuels are exhaustible natural resources.
Answer:
Fossil fuels require millions of years to form from the dead vegetation and animals that got buried deep inside the earth. They require high temperature and pressure for their formation, which cannot be provided in the laboratory. Thus, fossils are limited. Therefore, the use of fossil fuels at this rate will lead to their exhaustion. Since, the time taken for the formation of fossil fuels is much higher than the human life span, they are considered as exhaustible natural resources.

Question 7.
Describe characteristics and uses of coke.
Answer:
Coke is a type of coal. It is a tough, porous and black substance. It is almost pure form of carbon. Coke is much cleaner than coal and provides more energy on burning. It is used in the manufacture of steel and in the extraction of many minerals.

Question 8.
Explain the process of formation of petroleum.
Answer:
Petroleum is a dark, oily and thick liquid. It is a mixture of various fractions. Petroleum was formed by the decomposition of the remains of tiny plants and animals under the sea. It is believed that millions of years ago, the tiny plants and animals which lived in the sea, died. Their dead bodies sank to the bottom of sea and were soon covered with mud and sand. Due to high pressure, heat, action of bacteria and in the absence of air. the dead remains of tiny plants and animals were slowly converted into petroleum. The petroleum thus formed got trapped between the two layers of impervious rock, forming an oil deposit.

The more volatile component of petroleum formed a gaseous cover over petroleum. Such a gaseous mixture covering the crude oil is known as natural gas.

Question 9.
The following table shows the total power shortage in India from 1991-1997. Show the data in the form of a graph. Plot shortage percentage for the years on the Y-axis and the year on the X-axis.

Answer:
Scale: Along X-axis: 1 unit = 1 year
Along Y-axis: 1 unit = 1%

NCERT Extended Learning Activities and Projects

Question 1.
Get an outline map of India. Mark the places in the map where coal, petroleum and natural gas are found. Show the places where petroleum refineries are situated.
Hint:
Do it yourself.

Question 2.
Choose any five families of your neighbourhood. Enquire whether their energy consumption (coal, gas, electricity, petrol, kerosene) has increased or decreased in the last five years. Enquire also about the measures they adopt to conserve energy.
Hint:
Do it yourself.

Question 3.
Find out the location of major thermal power plants in India. What could be the reasons for their being located at those places?
Hint:
Do it yourself.

Activity 1

Objective: To classify the resources as natural or man-made.
Materials Required: Pen and paper.
Procedure:

• Observe your surroundings and make a list of various materials used by us in daily life.
• Classify these materials as natural or man-made in a table as shown below.

Observation:

Conclusion: Natural resources like air, water, sunlight, etc., are present in nature while man-made resources like building, roads, plastics, etc., are synthesised by humans.

Fossil Fuels: Dead remains of organisms (plants or animals) which are more than 10,000 years old are called fossils. The fuels which are formed by the decomposition of fossils over millions of years are called fossil fuels, e.g., coal and petroleum.

Coal: Coal is a hard, black, combustible mineral that consists mainly of carbon. It is formed by the deeply buried remains of vegetation under high pressure and high temperature over millions of years. Since coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonisation.

Uses of Coal: Coal bums in air to produce heat and carbon dioxide. Coal is used as a fuel because it provides large amount of heat energy.
C + O₂ → CO₂

• Coal was used as a fuel in steam engines.
• Most of the thermal power plants still use coal as a fuel.
• Coal is still being used as a kitchen fuel in some households, dhabas and restaurants.
• Many useful products, like coke, coal-tar and coal gas, are made by processing coal.

Destructive distillation: When any substance is heated in the absence of air to form a number of different products, the process is known as destructive distillation. The products which are obtained by the process of destructive distillation of coal are coke, coal tar and coal gas.
i. Coke: Coke is an almost pure form of carbon, is tough, porous and black. Coke is used in the manufacture of steel and extraction of many metals.
ii. Coal Tar: It is a black thick liquid with an unpleasant smell. Coal tar is a mixture of about 200 substances. It is used as a raw material for making various items like synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, naphthalene balls, etc. It is used for making the surface of roads. Bitumen (a petroleum product) has almost replaced coal tar for making road surfaces.
iii. Coal Gas: Coal gas is produced during the processing of coke from coal. Coal gas is used as a fuel in many industries which are situated near coal mines.

Petroleum: Petroleum is a dark oily liquid and has a foul smell. It contains many constituents like petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc.

Formation of Petroleum: Petroleum was formed from the organisms living in the seas. When these organisms died, their bodies got settled at the bottom of the sea and eventually, layers of sand and clay got deposited over them. After millions of years in the absence of air, the high temperature and high pressure converted them into petroleum and natural gas. Today, we drill down through layers of sand, silt and rock to reach the rock formation that contains oil and natural gas deposits.

Refining of Petroleum: It is the process of separating the various constituents of petroleum and is carried out in a petroleum refinery. The various constituents of petroleum and their uses are as follows:
Various Constituents of Petroleum and their Uses

Natural Gas: Natural gas is considered important as this fossil fuel can easily be transported through pipes. It is stored as CNG (compressed natural gas) which is used for several purposes and is also used as a starting material for manufacturing many chemicals and fertilisers. Natural gas does not cause pollution and has a high calorific value.

Limitations of Natural Resources: Fossil fuels like coal, petroleum, etc., need millions of years to get transformed from dead bodies into fuels. But currently, their demands are so high that after a few hundred years there will be a scarcity of these resources. In addition, too much of air pollution is caused when these fuels are burnt. These fuels are also responsible for the problems associated with the global warming. Hence, it is very important to use these fuels wisely.

Some of the PCRA (Petroleum Conservation Research Association) recommendations for the conservation of petrol and diesel are as follows:

• Drive at constant and moderate speed as far as possible.
• Switch off the engine at traffic lights or at a places where you have to wait.
• Ensure correct tyre pressure.
• Ensure regular maintenance of the vehicle.

Class 8 Science Chapter 5 Coal and Petroleum Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is a natural resource?
Answer:
A resource which is obtained from nature is called a natural resource.

Question 2.
What do you mean by inexhaustible natural resources?
Answer:
The resources which are available in huge quantity and cannot be exhausted by human activities are called inexhaustible natural resources, e.g. sunlight, air, water, etc.

Question 3.
What is an exhaustible natural resource?
Answer:
A resource which is available in limited quantity and can be exhausted by human activities is called exhaustible natural resource, e.g., coal, petroleum, natural gas, etc.

Question 4.
Name the substance obtained from coal tar which is used to repel moths
and insects.
Answer:
Naphthalene ball.

Question 5.
Where was the first oil well drilled?
Answer:
The first oil well was drilled at Pennsylvania, USA, in 1859.

Question 6.
Name two fractions of petroleum which are used as fuel.
Answer:
Petrol and diesel.

Question 7.
Where and when was the first oil well drilled in India?
Answer:
In 1867, at Digboi in Assam.

Question 8.
What is diesel?
Answer:
Diesel is a fuel which is used in heavy vehicles, like buses and trucks. It is obtained after refining of petroleum.

Question 9.
Can we use all our natural resources forever?
Answer:
No, we cannot use all our natural resources forever because these are going to exhaust one day.

Question 10.
Define petrochemicals.
Answer:
The useful substances formed from natural gas and petroleum are called petrochemicals.

Question 11.
Why is coke not used as a fuel?
Answer:
It is more valuable when used in the extraction of metals, hence not used as a fuel.

Question 12.
How do we obtain coke from coal?
Answer:
By the process of destructive distillation.

Question 13.
Which fuel is promoted as a pollution-free fuel?
Answer:
CNG.

Question 14.
Why is natural gas a convenient fuel?
Answer:
It is because natural gas can be supplied through pipes in homes and is less polluting.

Question 15.
Write some places of India where oil is found.
Answer:
Assam, Gujarat, Bombay High and river basins of Godawari and Krishna.

Question 16.
Which constituents are separated from petroleum during refining?
Answer:
Petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc.

Short Answer Type Questions

Question 1.
What is coal? Write its uses.
Answer:
Coal is a black stone like substance. It is formed by the dead remains of the living organisms.
Uses of coal:

• Coal was used as a fuel in steam engines.
• Most of the thermal power plants still use coal as a fuel.
• Coal is still being used as kitchen fuel in some households, dhabas and restaurants.
• Many useful products like coke, coal tar and coal gas are made by processing coal.

Question 2.
What is coal-tar? How is it useful to us?
Answer:
The black liquid obtained during destructive distillation of coal is known as coal tar. It is thick, viscous and has unpleasant smell. It is a mixture of hundreds of substances. It is used as a raw material for making various items like synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, naphthalene balls, etc. It is used for making the surface of roads.

Question 3.
What happens after the petroleum is taken out of the oil well?
Answer:
Crude oil needs to be processed to obtain useful products. After extraction from oil wells, petroleum is sent to oil refineries. Petroleum is subjected to fractional distillation in the oil refinery where various constituents of petroleum are separated through this process.

Question 4.
Define refining of petroleum.
Answer:
Petroleum is a dark oily liquid. It has an unpleasant odour. It is a mixture of various constituents such as petrol, diesel, etc., and the process of separating these constituents from crude oil is called refining.

Question 5.
Why should we use certain resources, like coal and petroleum, judiciously?
Answer:
As we know that coal and petroleum are fossil fuels. The dead organisms take millions of year to get converted into these fuels. On the other hand, the known reserves of these fuels will last only a few hundred years. Apart from this, these products are not environment-friendly as burning of these fuels is a major cause of air pollution and their use is also linked to global warming. Hence, we should use these resources only when absolutely required.

Question 6.
What can be the potential effect of petroleum products on the environment?
Answer:
The effect of petroleum products on environment is as follows:

• While transporting petroleum and its products, there might be oil spillage.
• The process of refining petroleum generates various products that can lead to air and water pollution.
• Drilling of petroleum may result into serious disturbances in the aquatic life.
• Any leakage in the tanks in which petroleum is stored may lead to pollution and deterioration of groundwater.

Question 7.
Differentiate between renewable and non-renewable sources of energy with one example of each.
Answer:

Question 8.
Write down the consequence of excessive usage and mining of coal and petroleum.
Answer:
Excessive usage and mining of coal and petroleum may:

• lead to energy crisis.
• result in creation of a large hollow space underneath which may cause minor earthquakes or landslides.
• lead to the greenhouse effect, acid rain and many health-related problems.

Question 9.
Why is coke considered a better fuel than coal? Give three reasons.
Answer:
Coal and coke are both fuels. But, coke is considered to be a better fuel than coal because of the following reasons:

• Coke has higher calorific value than coal. So, coke produces more heat than the same mass of coal.
• Coke does not produce smoke on burning. So, there is lesser air pollution when coke is burnt as compared to the burning of coal.

Question 10.
What is the basis of the process of fractional distillation of petroleum?
Answer:
The different components of petroleum have distinctly different boiling points. These components get separated in the fractional distillation tower when their boiling point is reached. The component having the maximum boiling point is at the bottom while the component having the minimum boiling point is at the top.

Long Answer Type Questions

Question 1.
Describe some ways to conserve fossil fuels.
Answer:
Economic and controlled consumption of fossil fuels can help conserving our natural resources. Following ways and measures can conserve our fossil fuels:

• Vehicles should be driven at constant and moderate speed.
• Engines should be switched off at traffic lights or other temporary halts.
• Proper and regular maintenance of vehicles should be done.
• Vehicle pooling can reduce the number of vehicles plying on the road, thereby decreasing fuel consumption.
• At home, gas stoves should be cleaned properly and burners should not be left burning unnecessarily.
• Pressure cookers should be preferred to pans. If pans are being used, they should be properly covered and their bottoms should not have deposits of burnt oil.
• Small pans and burners should be used and pulses, etc., should be soaked in water before cooking them.

Question 2.
What are the different constituents of petroleum and their uses?
Answer:
Following are the various constituents of petroleum oil obtained during fractional distillation in oil refineries:

• LPG or petroleum gas is used as a fuel for home and industry.
• Petrol is used as a motor fuel, aviation fuel and a solvent for dry cleaning.
• Kerosene is used as a fuel for stoves and lamps and also in jet aircrafts.
• Diesel is used as a fuel for heavy motor vehicles and electric generators.
• Lubricating oil is used for many lubricating purposes.
• Paraffin wax is used in ointments, candles and Vaseline.
• Bitumen is used in paints and also to surface the roads.
• Petrochemicals are used in the manufacture of detergents, polyester, nylon fibres, polythene and other man-made plastics.

Question 3.
Discuss the advantages of using compressed natural gas.
Answer:
Advantages of CNG:

• CNG is a very important fossil fuel because it is easy to transport through pipes.
• CNG is also used for power generation and now used as a fuel for vehicles because it is less polluting.
• It is a cleaner fuel.
• Due to the absence of any lead or benzene content in CNG, the lead fouling of spark plugs is eliminated.
• CNG-powered vehicles have low maintenance cost when compared with other fossil fuel-powered vehicles.
• CNG fuel systems are sealed which prevents any spill or evaporation losses.
• CNG mixes easily and evenly in air being a gaseous fuel.
• CNG is less likely to auto-ignite on hot surfaces, since it has a high auto-ignition temperature and a narrow range of flammability. Thus it is less polluting and more efficient.

Question 4.
What is destructive distillation of coal? Describe the constituents obtained from this process.
Answer:
The process in which a solid material (usually coal or wood) is heated at high temperature in absence of air to make coke, coal tar and charcoal is called. It is called ‘destructive’ because the chemical composition of the end product is significantly different from that of the input material.

a. Coke: Coke is almost pure form of carbon, is tough, porous and black. Coke is used in manufacture of steel and extraction of many metals.

b. Coal tar: It is a black thick liquid with an unpleasant smelt. Coal tar is a mixture of about 200 substances. It is used as a raw material for making various items, like synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, naphthalene balls, etc. It is used for making the surface of roads. Bitumen (a petroleum product) has almost replaced coal tar for making road surface.

c. Coal gas: Coal gas is produced during the processing of coke from coal. Coal gas is used as a fuel in many industries which are situated near coal mines.

Question 5.
Prakash worked in an MNC which is 20 km away from the society. He had a CNG vehicle and he displayed a notice in his society informing the people that if anybody is interested to pool a car, feel free to contact him for the same.
a. What is the fuel used in CNG vehicle and how it is better than petrol?
b. Mention two harmful effects/ disadvantages of petrol as a fuel.
Answer:
a. The compressed natural gas and methane is the fuel used in CNG vehicles. Compressed natural gas is a clean-burning fuel. It is actually the cleanest of all fossil fuels. Since natural gas is composed mainly of methane, burning it produces carbon dioxide and water vapour. These are the same compounds we exhale when we breathe. On the other hand, petroleum produces higher carbon emissions, nitrogen oxides and sulphur dioxide. Burning fuel oil also produces ash particulates that worsen pollution,

b. Two harmful effects of petrol are:

• It can lead to environmental pollution.
• It can be harmful to health.

Picture-Based Questions

Question 1.
Observe the given figure and answer the following questions:

a. Name the substance shown.
b. Name the process by which it is obtained.
c. Give any three uses of this substance.
Answer:
a. Coal tar.
b. Destructive distillation.
c. It is used in the manufacturing of dyes, drugs, paints, naphthalene balls, etc.

Question 2.
Draw a line diagram to show the position of layers of natural gas, petroleum and water deposits.
Answer:

These NCERT Solutions for Class 6 Maths Chapter 14 Practical Geometry InText Questions and Answers are prepared by our highly skilled subject experts.

NCERT Solutions for Class 6 Maths Chapter 14 Practical Geometry InText Questions

NCERT In-text Question Page No. 286
Question 1.
In Step 2 of the construction using ruler and compasses, what would happen if we take the length of radius to be smaller than half the length of \(\overline{\mathrm{AB}}\) ?
Answer:
In case we take the radius smaller than half of the length of \(\overline{\mathrm{AB}}\), the arcs will not intersect each other at two points P and Q.

NCERT In-text Question Page No. 289
Question 1.
In Step 2 above, what would happen if we take radius to be smaller than half the length BC?
Answer:
If we take radius to be smaller than half of BC, the arcs drawn with centres B and C will not intersect each other.

NCERT In-text Question Page No. 290
Question 1.
How will your construct at 15° angle?
Answer:
Steps of construction:
Step I: Construct an angle ∠ABC of 60°.
Step II: Bisect ∠ABC to get an angle of 30°
i. e. ∠ABD = 30°.

Step III: Bisect ∠ABD, such that \(\overline{\mathrm{BE}}\) is bisector of ∠ABD.
Thus, ∠ABD = \(\frac { 1 }{ 2 }\)(30°) = 15°.

NCERT In-text Question Page No. 291 
Question 1.
How will you construct a 150° angle?
Answer:
Steps of construction:
Step I: Draw a line I and mark a point O on it.
Step II: With centre O and a convenient radius, draw an arc intersecting I at A.
Step III: With the same radius and centre at A, draw an arc to cut the first arc at B.
Step IV: Again with the same radius and centre at B, draw another arc to intersect the
first arc at C.

Step V : Once again with the same radius and centre at C, draw an arc to cut the first are at D.
Step VI: Now, bisect ∠COD, such that ∠COE = ∠EOD = 30°.
Step VII: Since, 150° = 120° + 30°, therefore ∠AOC + ∠COE = ∠AOE. Thus, ∠AOE is the required angle whose measure is 150°.

Question 2.
How will you construct a 45° angle?
Answer:
Steps of construction :
Step I: Construct an angle of 90° as shown in
the figure. ∠POQ = 90°.

Step II: Draw OR, the angle bisector of ∠POQ such that \(\frac { 1 }{ 2 }\)– [∠POQ] = \(\frac { 1 }{ 2 }\) (90°) = 45° or ∠POR = 45°

These NCERT Solutions for Class 6 Maths Chapter 2 Whole Numbers InText Questions and Answers are prepared by our highly skilled subject experts.

NCERT Solutions for Class 6 Maths Chapter 2 Whole Numbers InText Questions

NCERT In-text Question Page No. 28

Question 1.
Write the predecessor and successor of 19; 1997; 12000; 49; 100000.
Answer:
Predecessor means the number before the given number and Successor is just opposite of it, the number after given number.

Question 2.
Is there any natural number that has no predecessor?
Answer:
Yes, the smallest natural number 1 has no predecessor.

Question 3.
Is there any natural number which has no successor? Is there a last natural number?
Answer:
(i) No, there is no natural number which has no successor.
(ii) No, there is no last natural number.

NCERT In-text Question Page No. 29

Question 1.
Are all natural numbers also whole numbers?
Answer:
Yes, all natural numbers are whole numbers.

Question 2.
Are all whole numbers also natural numbers?
Answer:
No, all whole numbers are not natural numbers. Because 0 is a whole number but it is not a natural number.

Question 3.
Which is the greatest whole number?
Answer:
Since, every whole number has a successor. .’. There is no greatest whole number.

NCERT In-text Question Page No. 30

Question 1.
Find 4 + 5; 2 + 6; 3 + 5 and 1 + 6 using the number line.
Answer:
(i) 4 + 5

Let us start from 4. Since, we have to add 5 to this number, we make 5 jumps to the right. Each jump being equal to 1 unit. After five jumps we reach at 9 (as shown above).
∴ 4 + 5 = 9

(ii) 2 + 6

Let us start from 2. Since, we have to add 6 to this number, we make 6 equal jumps, each jump being equal to 1 unit, to the right and reach to 8.
∴ 2 + 6 = 8

(iii) 3 + 5

We have to add 5 to 3.
∴ start from 3. We make 5 equal jumps. Each jump being equal to 1 unit (as shown in the figure) to the right and reach to 8.
∴ 3 + 5 = 8.

(iv) 3 + 5

As we have to add 6 to 1, therefore, we start from 1 and make 6 equal jumps to the right. Each jump being equal to 1 unit.
We reach to 7.
∴ 1 + 6 = 7

Question 2.
Find 8 -3; 6 -2; 9-6 using the number line.
Answer:
(i) 8 – 3

To subtract 3 from 8, start from 8 and make 3 equal jumps towards left. Each jump being equal
i to 1 unit.
So, we reach at 5,

(ii) 6 – 2

To subtract 2 from 6, we start from 6. Make 2 equal jumps towards left. Each jump being equal
to 1 unit.
So, we reach at 4.

(iii) 9 – 6

To subtract 6 from 9, we start from 9. Make 6 equal jumps towards left. Each jump being equal to 1 unit.
So, we reach at 3.

NCERT In-text Question Page No. 31

Question 1.
Find 2 x 6; 3 x 3; 4 x 2 using the number line.
Answer:
(i) 2 x 6

Starting from 0, move 2 units at a time to the right.
Make 6 such moves. So, we reach at 12
∴ 2 x 6 = 12

(ii) 3 x 3

Starting from 0, move 3 units at a time to the right. Make 3 such moves. So, we reach at 9,
∴ 3 x 3 = 9

(iii) 4 x 2

Starting from 0, move 4 units at a time to the right. Make 2 such moves.
So, we reach at 8,
∴ 4 x 2 = 8

NCERT In-text Question Page No. 37

Question 1.
Find: 7 + 18 + 13; 16 + 12 + 4
Answer:
(i) 7 + 18 + 13 = (7 + 13) + 18
= 20 + 18 = 38
(ii) 16 +12 + 4 = (16 + 4) + 12
= 20 + 12 = 32

Question 2.
Find:
25 x 8358 x 4; 625 x 3759 x 8
Answer:
(i) 25 x 8358 x 4 = (25 x 4) x 8358
(Using associativity of whole numbers)
= (100) x 8358 = 835800

(ii) 625 x 3759 x 8 = (625 x 8) x 3759 (Using associativity of whole numbers)
= 500 x 3759
= 5 x 1000 x 3759
= (3759 x 5) x 1000
= 18795 x 1000 = 18795000
∴ 625 x 3759 x 8 = 18795000

NCERT In-text Question Page No. 39

Question 1.
Find 15 x 68; 17 x 23; 69 x 78 + 22 x 69 using distributive property.
Answer:
(i) 15 x 68 = (10 + 5) x 68
= (10 x 68) + (5 x 68)
(By distributivity of multiplication over addition)
= 680 + 340 = 1020

(ii) 17 x 23 = 17 x (20 + 3)
= (17 x 20)+ (17 x 3)
= (17 x 20)+ (17 x 3)
(By distributivity of multiplication over addition)
= 340 + 51 = 391

(iii) 69 x 78 + 22 x 69 = 69 [78 + 22]
= 69 [100]
= 6900
Thus, 69 x 78 + 22 x 69 = 6900

NCERT In-text Question Page No. 42

Question 1.
Which numbers can be shown only as a line?
Answer:
The numbers 2, 5, 7, 11, 13, 14, 17, 19, … can be shown only as a line.

Question 2.
Which can be shown as squares?
Answer:
The numbers 4, 9, 16, 25 … can be shown as squares.

Question 3.
Which can be shown as rectangles?
Answer:
The numbers like 4,6, 8,9,10,12,… can be shown as rectangles.

Question 4.
Write down the first seven numbers that can be arranged as triangles, e.g. 3, 6,.
Answer:
We have

Thus, the first seven triangular numbers are: 3, 6, 10, 15, 21, 28 and 36.

Question 5.
Some numbers can be shown by two rectangles, for example.
There can be many such examples. Some of them are as follows:

Give at least five other such examples.
Answer:
There can be many such examples. Some of them are as follows:

These NCERT Solutions for Class 8 Science Chapter 4 Materials: Metals and Non-Metals Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Materials: Metals and Non-Metals NCERT Solutions for Class 8 Science Chapter 4

Class 8 Science Chapter 4 Materials: Metals and Non-Metals Textbook Exercise Questions and Answers

Page 53-55

Question 1.
Which of the following can be beaten into thin sheets?
a. Zinc
b. Phosphorus
c. Sulphur
d. Oxygen
Answer:
a. Zinc

Question 2.
Which of the following statements is correct?
a. All metals are ductile.
b. All non-metals are ductile.
c. Generally, metals are ductile.
d. Some non-metals are ductile.
Answer:
c. Generally, metals are ductile.

Question 3.
Fill in the blanks:
a. Phosphorus is a very …………….. non-metal.
b. Metals are …………….. conductors of heat and ……………..
c. Iron is …………….. reactive than copper.
d. Metals react with acids to produce …………….. gas.
Answer:
a. reactive,
b. good, electricity,
c. more,
d. hydrogen

Question 4.
Mark ‘T’ if the statement is true and ‘F’ if it is false.
a. Generally, non-metals react with acids. ( )
b. Sodium is a very reactive metal. ( )
c. Copper displaces zinc from zinc sulphate solution. ( )
d. Coal can be drawn into wires. ( )
Answer:
a. False
b. True
c. False
d. False

Question 5.
Some properties are listed in the following table. Distinguish between metals and non-metals on the basis of these properties.

Answer:

Question 6.
Give reasons for the following:
a. Aluminium foils are used to wrap food items.
b. Immersion rods for heating liquids are made up of metallic substances.
c. Copper cannot displace zinc from its salt solution.
d. Sodium and potassium are stored in kerosene.
Answer:
a. Aluminium reacts with air to make a coating of aluminium oxide on it. This layer prevents aluminium from further reactions with any substance. Due to this, aluminium foils are used to wrap food items because it does not react with food.

b. Metals are good conductors of heat and have a high melting point. Immersion rods need to heat up quickly and should not melt at high temperatures. Hence, immersion rods for heating liquids are made up of metallic substances.

c. Copper is less reactive than zinc. Hence, copper cannot displace zinc from its salt solution.

d. Sodium and potassium are highly reactive and react vigorously with water even at room temperature. The reaction is highly exothermic and the reaction mixture instantly catches fire. Sodium and potassium are stored in kerosene to prevent this reaction and to prevent accidental fire.

Question 7.
Can you store lemon pickle in an aluminium utensil? Explain.
Answer:
No, it is not possible to store lemon pickle in an aluminium utensil because lemon pickle is acidic and can react with aluminium (metal) liberating hydrogen gas. This may spoil the pickle.

Question 8.
Match the substances given in Column A with their uses given in Column B.

Answer:
(i) → d,
(ii) → e,
(iii) → c,
(iv) → f,
(v) → b,
(vi) → a

Question 9.
What happens when
a. Dilute sulphuric acid is poured on a copper plate?
b. Iron nails are placed in copper sulphate solution?
Write word equations of the reactions involved.
Answer:
a. Copper does not react with dilute sulphuric acid. So, no reaction takes place when dilute sulphuric acid is poured on a copper plate. However, when concentrated sulphuric acid is poured on copper plate, hydrogen gas evolves along with the formation of blue coloured copper sulphate crystals.
Cu + H₂SO₄ (conc.) → CuSO₄ + H₂O
Copper + Dilute sulphuric acid → No reaction

b. When iron nails are placed in copper sulphate solution, the blue colour of copper sulphate solution is replaced by a light green colour. This happens because, iron being more reactive than copper, displaces copper from copper sulphate and makes iron sulphate solution.
Copper sulphate (blue) + Iron → Iron sulphate (light green) + Copper
Fe + CuSO₄ → FeSO₄ + Cu

Question 10.
Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
a. How will she find the nature of the gas?
b. Write down word equations of all the reactions taking place in this process.
Answer:
a. Saloni should bring a wet blue litmus paper near the evolved gas. If litmus paper turns to red, it indicates that the evolved gas is acidic in nature.

b. Carbon (in charcoal) reacts with oxygen to produce carbon dioxide gas.
C + O₂ → CO₂
Carbon dioxide reacts with water to form carbonic acid.
CO₂ + H₂O → H₂CO₃ (acidic)

Question 11.
One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?
Answer:
Jewellers use aqua regia to clean the jewellery. Gold is an inert metal which does not react with acids. But aqua regia is a mixture of hydrochloric acid and nitric acid in 3 : 1 ratio. It is so potent that it even dissolves gold and silver. Some of the gold is thus lost during the cleaning of jewellery. This explains the weight loss in jewellery.

NCERT Extended Learning Activities and Projects

Question 1.
Prepare Index Cards for any four metals and four non-metals. The card should have information like name of metal/non-metal; its physical properties, chemical properties and its uses.
Hint:
Uses of Metals

• Iron metal is used for making cooking vessels, water boilers, stoves, tools, wires, nails, bolts, electromagnets, etc.
• Aluminium is a very light metal so it is used in making the aircraft bodies,
• Copper is most widely used for making electric wires and all things related to electricity because it is a good conductor of electricity,
• Silver is widely used for making jewellery.

Uses of Non-metals

• Phosphorous is used in matchbox industry and in fertilisers,
• Iodine is used as an antiseptic,
• Oxygen is essential for all living beings.
• Sulphur is used for making firecrackers, gun powder and sulphuric acid.

Question 2.
Visit a blacksmith and observe how metals are moulded.
Hint:
Do it yourself.

Question 3.
Suggest an experiment to compare the conductivity of electricity by iron, copper, aluminium and zinc. Perform the experiment and prepare a short report on the results.
Hint:
Let us make a simple circuit by connecting one end of the torch bulb to a cell and another end of torch bulb to an aluminium metal strip or wire and back to the cell (as shown in figure).
Repeat the same activity with different metal strips like iron, copper and zinc.

In the case of copper, we will observe that the bulb glows the fastest and more brightly than others, while in case of iron, the bulb glows the slowest and less brightly than the others.
Hence, the sequential order of their decreasing electrical conductivity is: copper → aluminium → zinc → iron.

Question 4.
Find out the locations of the deposits of iron, aluminium and zinc in India. Mark these in an outline map of India. In which form are the deposits found? Discuss in the class.
Hint:
Iron is found as haematite ore, aluminium as bauxite and zinc as zinc blende or zinc carbonate.

Question 5.
Discuss with your parents/ neighbours/goldsmiths why gold is preferred for making jewellery.
Hint:
Gold is the most ductile and least reactive metal with large amount of lustre.

Activity 1

Objective: To show that the oxides of non¬metals (e.g., sulphur) are acidic in nature.
Materials Required: Powdered sulphur, deflagrating spoon, gas jar, glass cover, water, litmus solution.
Procedure:

• Take a small amount of powdered sulphur in a deflagrating spoon.
• Heat it over a flame.
• As soon as the sulphur starts burning, introduce the spoon into a gas jar.
• Cover the gas jar with a glass cover.
• When the reaction is over, remove the spoon and add 5 mL of water into the jar and replace the glass cover.
• Shake the jar and add about 1 mL blue litmus solution in it.
• Shake it and observe the colour change.

Observation: When the solution of sulphur is mixed with blue litmus, it turns red.
Conclusion: Sulphur is a non-metal and its oxide is acidic in nature.

ii. Reaction with Water:
Metals: When a metal reacts with water, a metal hydroxide and hydrogen gas are formed. Different metals react with water at different temperatures. Some metals react vigorously with water, while some others do not react with water at all.
Metal + Water → Metal hydroxide + Hydrogen

Example: Sodium is a highly reactive metal and reacts vigorously with water. This is a highly exothermic reaction. During this reaction, sodium catches fire because of too much heat being evolved. Due to this, sodium is stored in kerosene to prevent accidental fires.

Non-metals: Generally, non-metals do not react with water though they may be very reactive in air. Some non-metals, such as phosphorus, react with air vigorously. It catches fire if exposed to air. Hence, phosphorus is stored in water.

iii. Reaction with Acids:
Metals: Metals give hydrogen gas every time they react with a dilute acid.
Metal + Acid → Metal salt + Hydrogen
Example: Zinc gives hydrogen gas along with zinc chloride when it reacts with hydrochloric acid.

Similarly, zinc also gives hydrogen gas when it reacts with sulphuric acid.
Also, metals like copper do not react with dilute sulphuric acid even on heating but it reacts with concentrated sulphuric acid.

Non-metals: Non-metals do not react with acids.

Activity 2

Objective: To show the reaction of metals and non-metals with dilute hydrochloric acid and dilute sulphuric acid.
Materials Required: Test tube, metals and non-metals (magnesium ribbon, aluminum foil, iron filings, charcoal and sulphur powder), hydrochloric acid, sulphuric acid and matchbox.
Procedure:

• Take a samples of metals and non-metals in separate test tubes and label them as A, B, C, D and E.
• With the help of a dropper, add 5 mL of dilute hydrochloric acid to each test tube one by one.
• Observe the reaction carefully. If no reaction occurs in the cold solution, warm the test tube gently.
• Bring a burning match stick near the mouth of each test tube.
• Repeat the same activity using dilute sulphuric acid in place of dilute hydrochloric acid.

Observations:

Conclusion: Metals usually displace hydrogen from dilute acids and liberate hydrogen gas while non-metals do not react with dilute acids and no hydrogen gas is evolved.

iv. Reaction with Bases:
Metals: Metals give hydrogen gas when they react with a base. This gas produces a pop sound when a burning matchstick is put above the mouth of the beaker containing reaction mixture.
Example: Aluminium metal reacts with sodium hydroxide to fonn hydrogen gas and sodium aluminate.

Non-metals: Reactions of bases with non-metals are complex.
Aqua regia: It is a freshly-prepared solution of concentrated HCl and concentrated HNO₃ in the ratio of 3 : 1 respectively. It can dissolve even gold and platinum.

Displacement reaction: When a more reactive metal displaces a less reactive metal from its salt solution, it is called a displacement reaction.
Metal A + Salt solution of metal B → Salt solution of metal A + Metal B
In the above equation, metal A is more reactive than metal B, so B will be displaced.

Example 1: When aluminium metal is dipped in the solution of copper sulphate, it forms aluminium sulphate and copper.

Example 2: When iron reacts with solution of copper sulphate, it gives iron sulphate and copper.

In the above two reactions, aluminium and iron are more reactive than copper, that is why they displaced copper from the copper sulphate solution.

Activity 3

Objective: To show displacement reaction with the help of an activity.
Materials Required: Five beakers (100 mL), water, zinc sulphate, iron sulphate, copper sulphate, zinc granules, iron nails and copper turnings
Procedure:

• Take five 100 mL beakers and label them as A, B, C, D and E.
• Take about 50 mL of water in each beaker.
• Dissolve in beakers A and B, a teaspoonful of copper sulphate (CuSO₄), in beakers C, D and E zinc sulphate (ZnSO₄), iron sulphate (FeSO₄) and zinc sulphate (ZnSO₄), respectively.
• Put zinc granules, iron nail, copper turnings, copper turnings and iron nail in beakers A, B, C, D and E, respectively.
• Observe the changes.

Reactions:
A : CuSO₄ + Zn → ZnSO₄ + Cu
B : CuSO₄ + Fe → FeSO₄ + Cu
C : ZnSO₄ + Cu → No change
D : FeSO₄ + Cu → No change
E : ZnSO₄ + Fe → No change

Observation: We see that in beakers A and B, colour is changed while in C, D and E, there is no change of colour. Beakers A and B show displacement reactions.

Conclusion: We have seen that only a more reactive metal displaces a less reactive metal from its salt solution but a less reactive metal does not do so.

Uses of Metals:
i. Metals are used in making wires and sheets, which are used for various purposes. For example, copper and aluminium wires are used for the conduction of electricity, in electrical equipments, etc. Iron wires are used for fencing and various other purposes. Iron sheets are often used for making roof sheds.
ii. Metals are used in making machinery, automobiles, utensils, industrial gadgets, water boilers, etc.
iii. Some metals like iron, sodium and calcium are essential parts of our body.
iv. Alloys: An alloy is a solid mixture of two or more metals or a metal and a non¬metal.
a. Alloys of metals are used in making coins, satellites, stainless steel, wooden ships sheathing and casting. For example, Muntz is an alloy of 60% Cu and 40% Zn. Similarly, brass is an alloy of copper and zinc.
b. Alloys like duralumin, have great strength. It is used in aircrafts, pressure cookers, automobiles, etc. Naval brass is used for marine and engineering castings.

Uses of Non-metals:

• The number of non-metals is very less in comparison to metals, but non-metals are very useful for us. So far, only about 22 non-metals have been discovered.
• Non-metals, such as oxygen, are essential for our life which all living being inhale during breathing.
• Sodium chloride (common salt) cannot be formed without chlorine (a non¬metal) which is a necessary ingredient of our food.
• Non-metals are used in fertilisers to enhance the growth of plants. For example, NPK fertilisers.
• They are also used in water-purification process. Chlorine, a non-metal, is used as a disinfectant in water treatment plants.

Class 8 Science Chapter 4 Materials: Metals and Non-Metals Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Define metal.
Answer:
Metal is usually a hard substance which is lustrous, sonorous, ductile and is a good conductor of heat and electricity.

Question 2.
Define non-metal.
Answer:
Non-metal is a substance which is usually soft, non-lustrous, non-sonorous, non-ductile and is a bad conductor of heat and electricity.

Question 3.
What is lustre?
Answer:
The typical shine of a metal is called lustre.

Question 4.
Name two metals which can be cut with a knife?
Answer:
Sodium and potassium.

Question 5.
Name a non-metal which is a good conductor of electricity.
Answer:
Graphite.

Question 6.
An element forms an oxide which is acidic in nature. Is the element a metal or a non-metal?
Answer:
Non-metal.

Question 7.
Give the chemical equation representing the reaction of iron with oxygen.
Answer:
2Fe + O₂ + H₂O → Fe₂O₃.xH₂O

Question 8.
What is the chemical formula of magnesium oxide?
Answer:
MgO.

Question 9.
Do metals also react with bases?
Answer:
Metals also react with bases like sodium hydroxide and produce hydrogen gas.

Question 10.
What is the chemical formula of copper hydroxide?
Answer:
Cu(OH)₂.

Question 11.
What are metalloids?
Answer:
The elements which show the properties of both metals and non-metals e.g., silicon and arsenic, are called metalloids.

Question 12.
What is a displacement reaction?
Answer:
It is a reaction in which a more reactive metal displaces a less reactive metal from its salt solution.

Question 13.
Give an example of a displacement reaction.
Answer:
CuSO₄ (copper sulphate) + Zn (Zinc) → ZnSO₄ (Zinc sulphate) + Cu (Copper).

Question 14.
Give the name of one metal and one non-metal which exist in liquid state.
Answer:
Mercury (liquid metal) and bromine (liquid non-metal).

Short Answer Type Questions

Question 1.
Copper coins develop greenish patches when kept unused for a long time. Why?
Answer:
When copper is exposed to moist air for a long time, it acquires a greenish coating. The green coat is a mixture of copper hydroxide and copper carbonate which is formed as a result of reaction of copper with moist air.
2Cu + H₂O + CO₂ + O₂ → Cu(OH)₂ + CuCO₃
Due to this, copper coins develop greenish patches when kept unused for a long time.

Question 2.
What happens when a magnesium ribbon is heated in the presence of air?
Answer:
Magnesium bums with a bright dazzling light in the presence of oxygen and forms a white powder of magnesium oxide.
2Mg(s) + O₂(g) → 2MgO(s)

Question 3.
How does a base react with metals and non-metals?
Answer:
Reaction of base with metals and non-metals is as follows:
a. Metals react with bases to produce metal salt and hydrogen gas.
For example: Aluminium + Sodium hydroxide → Sodium aluminate + Hydrogen gas
b. Reaction of non-metals with bases is much complex.

Question 4.
What happens when zinc granules are kept in copper sulphate solution?
Answer:
When zinc granules are kept in copper sulphate solution, the blue colour of copper sulphate disappears and the solution becomes colourless. Zinc is more reactive than copper and hence displaces copper from copper sulphate solution and forms zinc sulphate solution which is colourless.
CuSO₄ (Blue) + Zn → ZnSO₄ (Colourless) + Cu

Question 5.
What happens when copper turnings are kept in zinc sulphate solution?
Answer:
Copper is less reactive than zinc. Hence, copper cannot displace zinc from its salt solution. Hence, no reaction takes place when copper turnings are kept in zinc sulphate solution.

Question 6.
Explain an activity to test the nature of rust.
Answer:
Collect some quantity of rust after a reaction between iron, oxygen and water. Dissolve it in a very little amount of water. Shake the mixture of rust and water well. Test the solution with red and blue litmus papers. It will be observed that the red litmus paper turns blue. It shows that the nature of rust is basic.

Question 7.
Metals are good conductor of electricity. Explain this with the help of an activity.
Answer:
Make an electric circuit as shown in the given figure. The circuit is used to test whether electricity can pass through a given material or not. Repeat this activity with different materials as shown in the table. Observe whether the bulb glows or not in each case and identify whether they are good or bad conductors of electricity.

It will be observed that iron rod/nail and copper wire are good conductors while rolled sulphur piece and coal piece are bad conductors.

Question 8.
Explain the reaction of sodium with water with the help of an activity.
Answer:
Take a 250 mL beaker/glass tumbler. Fill half of it with water. Now carefully cut a small piece of sodium metal. Dry it using filter paper and wrap it in small pieces of cotton. Put the sodium piece wrapped in cotton into the beaker. Observe carefully. During observation, keep yourself away from the beaker. When reaction stops, touch the beaker. Now test the solution with red and blue litmus papers. The solution turns red litmus into blue.

This activity indicates that sodium is highly reactive and it reacts vigorously with water. A lot of heat is generated in the reaction to form basic solution of sodium hydroxide.
Sodium + Water → Sodium hydroxide + Heat

Question 9.
Have you ever seen a blacksmith beating an iron piece? Find a change in the shape of these pieces on beating. Would you expect a similar change in a wood log on beating?
Answer:
Yes, we have seen blacksmith beating the iron pieces. We have seen the changes in the shape on beating. It increases in size and it does not break. A similar change in a wood log cannot be expected at all. A wood log will break into pieces if beaten.

Question 10.
State three reasons (of which at least one must be chemical) for believing that sulphur is a non-metal.
Answer:

1. Sulphur is neither malleable nor ductile. It cannot be hammered into sheets or drawn into wires. Sulphur is brittle and breaks into pieces when hammered.
2. Sulphur does not conduct electricity.
3. Sulphur forms an acidic oxide, i.e., sulphur dioxide, hence it is a non-metal.

Question 11.
Concentrated sodium hydroxide solution cannot be stored in aluminum containers. Give reasons.
Answer:
Aluminium metal will react will NaOH base and liberate highly inflammable hydrogen gas.
2Al + 2NaOH + 2H₂O → 2NaAlO₂ + 3H₂
Hence, sodium hydroxide solution cannot be kept in aluminium containers.

Question 12.
What happens when metals react with dilute acids? Write equations of the reactions of magnesium and zinc metals with dilute hydrochloric acid.
Answer:
Metals form their respective salts when they react with dilute acids and liberate hydrogen gas.
Metal + dilute acid → Metal salt + Hydrogen

a. Reaction of magnesium metal with dilute hydrochloric acid:
Magnesium chloride and hydrogen gas are formed when magnesium reacts with dilute hydrochloric acid.
Mg + 2HCl → MgCl₂ + H₂

b. Reaction of aluminium with dilute hydrochloric acid: Aluminium chloride and hydrogen gas are formed.
2Al + 6HCl → 2AlCl₃ + 3H₂

Question 13.
A solution of copper sulphate was kept in an iron pot. After a few days, the iron pot was found to have a number of holes in it. Write the reaction that took place. Explain this reaction.
Answer:
Iron is more reactive than copper. Iron displaces copper from copper sulphate solution and forms iron sulphate. Hence, holes appear on the pot as iron gets dissolved in the solution.
Fe + CuSO₄ (aq) → FeSO₄ (aq) + Cu

Question 14.
Why are aluminium and zinc known as self protecting metals?
Answer:
Aluminium and zinc are self protecting metals because when they come in contact with air, they form their respective oxides that form an impermeable layer on their surface which prevents further attack of air on the metal.

Long Answer Type Questions

Question 1.
What is the difference between the chemical properties of metals and non-metals?
Answer:

Question 2.
State five uses each of metals and non-metals.
Answer:
Uses of metals:

• Lead metal is used in making car batteries.
• Zinc is used for galvanizing iron to protect it from rusting.
• Iron, copper and aluminium are used to make utensils.
• Copper and aluminium metals are used to make electrical wires.
• Aluminium is used to make aluminium foil for packing food materials.

Uses of non-metals:

• Hydrogen is used in the hydrogenation of vegetable oils.
• Carbon is used to make electrodes of electrolytic cells and dry cells.
• Nitrogen is used in the manufacture of ammonia, nitric acid and fertilisers.
• Sulphur is used for producing sulphuric acid.
• Liquid hydrogen is used as rocket fuel.

Question 3.
You are given samples of three metals-sodium, magnesium and copper. Suggest any two activities to arrange them in order of their decreasing reactivities.
Answer:
a. Activity 1: When sodium, magnesium and copper are left in air, sodium reacts vigorously with oxygen to form sodium oxide, magnesium reacts with oxygen to form magnesium oxide only on heating, whereas copper does not bum in air even on strong heating. It reacts only on prolonged heating. This shows that sodium is most reactive, then magnesium and copper is the least reactive among the three.

b. Activity 2: Sodium reacts vigorously with cold water to form sodium hydroxide and hydrogen, magnesium does not react with cold water but reacts with hot water to form magnesium hydroxide and hydrogen but copper does not react even with steam. This shows that sodium is highly reactive, magnesium is less reactive than sodium and copper is the least reactive among the three.

Picture-Based Questions

Question 1.
Observe the given diagram and answer the following questions:

a. Which property of metals is shown by this diagram?
b. Name two metals, other than iron, which have this property.
c. Name a non-metal which has this property.
Answer:
a. The given diagram shows the property of electrical conductivity of metals.
b. Copper and silver.
c. Graphite.

Question 2.
Observe the given figure and answer the following questions:

a. Which property of metals is shown in the figure?
b. Names the articles shown in the figure.
c. Name two metals which show this property.
d. Name two metals which lack this property.
Answer:
a. In the given figure, the property of malleability of a metal is shown.
b. Hammer and iron nails.
c. Gold and silver.
d. Sodium and potassium.

These NCERT Solutions for Class 6 Maths Chapter 14 Practical Geometry Ex 14.6 Questions and Answers are prepared by our highly skilled subject experts.

NCERT Solutions for Class 6 Maths Chapter 14 Practical Geometry Exercise 14.6

Question 1.
Draw ∠POQ of measure 75° and find its line of symmetry.
Answer:

Steps of construction:
(a) Draw a line l and mark a point O on it.
(b) Place the pointer of the compasses at O and draw an arc of any radius which intersects the line l at A.
(c) Taking same radius, with centre A, cut the previous arc at B.
(d) Join OB, then ∠BOA = 60 .
(e) Taking same radius, with centre B, cut the previous arc at C.
(f) Draw bisector of ∠BOC. The angle is of 90 . Mark it at D. Thus, ∠DOA = 90°
(g) Draw \(\overline{\mathrm{OP}}\) as bisector of ∠DOB. Thus, ∠POA = 75°

Question 2.
Draw an angle of measure 147° and construct its bisector.
Answer:
Steps of construction:
(a) Draw a ray \(\overline{\mathrm{OA}}\) .
(b) With the help of protractor, construct ∠AOB = 147°
(c) Taking centre O and any convenient radius, draw an arc which intersects the arms \(\overline{\mathrm{OA}}\) and \(\overline{\mathrm{OB}}\) at P and Q respectively.
(d) Taking P as centre and radius more than half of PQ, draw an arc.
(e) Taking Q as centre and with the same radius, draw another arc which intersects the previous at R.
(f) Join OR and produce it.
(g) Thus, \(\overline{\mathrm{OR}}\) is the required bisector of ∠AOB.

Question 3.
Draw a right angle and construct its bisector.
Answer:
Steps of construction:
(a) Draw a line PQ and take a point O on it.
(b) Taking O as centre and convenient radius, draw an arc which intersects PQ at A and B.
(c) Taking A and B as centres and radius more than half of AB, draw two arcs which intersect each other at C.
(d) Join OC. Thus, ∠COQ is the required right angle.
(e) Taking B and E as centre and radius more than half of BE, draw two arcs which intersect each other at the point D.
(f) Join OD. Thus, \(\overline{\mathrm{OD}}\) is the required bisector of ∠COQ.

Question 4.
Draw an angle of measure 153° and divide it into four equal parts.
Answer:
Steps of construction:
(a) Draw a ray \(\overline{\mathrm{OA}}\)
(b) At O, with the help of a protractor, construct ∠AOB = 153°.
(c) Draw \(\overline{\mathrm{OC}}\) as the bisector of ∠AOB.
(d) Again, draw \(\overline{\mathrm{OD}}\) as bisector of ∠AOC.
(e) Again, draw \(\overline{\mathrm{OE}}\) as bisector of ∠BOC.
(f) Thus, \(\overline{\mathrm{OC}}\), \(\overline{\mathrm{OD}}\) and \(\overline{\mathrm{OE}}\) divide ∠AOB in four equal arts.

Question 5.
Construct with ruler and compasses, angles of following measures:
(a) 60°
(b) 30°
(c) 90°
(d) 120°
(e) 45°
(f) 135°
Answer:
Steps of construction:
(a) 60°

(i) Draw a ray \(\overline{\mathrm{OA}}\).
(ii) Taking O as centre and convenient radius, mark an arc, which intersects \(\overline{\mathrm{OA}}\) at P.
(iii) Taking P as centre and same radius, cut previous arc at Q.
(iv) Join OQ.
Thus, ∠BOA is required angle of 60°.

(b) 30°

(i) Draw a ray \(\overline{\mathrm{OA}}\) .
(ii) Taking O as centre and convenient radius, mark an arc, which intersects \(\overline{\mathrm{OA}}\) at P.
(iii) Taking P as centre and same radius, cut previous arc at Q.
(iv) Join OQ. Thus, ∠BOA is required angle of 60°.
(v) Put the pointer on P and mark an arc.
(vi) Put the pointer on Q and with same radius, cut the previous arc at C. Thus, ∠COA is required angle of 30°.

(c) 90°

• Draw a ray \(\overline{\mathrm{OA}}\).
• Taking O as centre and convenient radius, mark an arc, which intersects \(\overline{\mathrm{OA}}\) at X.
• Taking X as centre and same radius, cut previous arc at Y.
• Taking Y as centre and same radius, draw another arc intersecting the same arc at Z.
• Taking Y and Z as centres and same radius, draw two arcs intersecting each other at S.
• Join OS and produce it to form a ray OB.
  Thus, ∠BOA is required angle of 90.

(d) 120°

• Draw a ray \(\overline{\mathrm{OA}}\).
• Taking O as centre and convenient radius, mark an arc, which intersects \(\overline{\mathrm{OA}}\) at P.
• Taking P as centre and same radius, cut previous arc at Q.
• Taking Q as centre and same radius cut the arc at S.
• Join OS.
  Thus, ∠AOD is required angle of 120°.

(e) 45°

• Draw a ray \(\overline{\mathrm{OA}}\) .
• Taking O as centre and convenient radius, mark an arc, which intersects \(\overline{\mathrm{OA}}\) at X.
• Taking X as centre and same radius, cut previous arc at Y.
• Taking Y as centre and same radius, draw another arc intersecting the same arc at Z.
• Taking Y and Z as centres and same radius, draw two arcs intersecting each other at S.
• Join OS and produce it to form a ray OB. Thus, ∠BOA is required angle of 90°.
• Draw the bisector of ∠BOA.
  Thus, ∠MOA is required angle of 45°.

(f) 135°

• Draw a line PQ and take a point O on it.
• Taking O as centre and convenient radius, mark an arc, which intersects PQ at A and B.
• Taking A and B as centres and radius more than half of AB, draw two arcs intersecting each other at R.
• Join OR. Thus, ∠QOR = ∠POQ = 90° .
• Draw OD the bisector of ∠POR.
  Thus, ∠QOD is required angle of 135°.

Question 6.
Draw an angle of measure 45° and bisect it.
Answer:
Steps of construction:
(a) Draw a line PQ and take a point O on it.
(b) Taking O as centre and a convenient radius, draw an arc which intersects PQ at two points A and B.
(c) Taking A and B as centres and radius more than half of AB, draw two arcs which intersect each other at C.
(d) Join OC. Then ∠COQ is an angle of 90.
(e) Draw \(\overline{\mathrm{OE}}\) as the bisector of ∠COE. Thus, ∠QOE = 45°
(f) Again draw \(\overline{\mathrm{OG}}\) as the bisector of ∠QOE.
Thus, ∠QOG = ∠EOG = 22\(\frac { 1 }{ 2 }\)°

Question 7.
Draw an angle of measure 135° and bisect it.
Answer:
Steps of construction:
(a) Draw a line PQ and take a point O on it.
(b) Taking O as centre and convenient radius, mark an arc, which intersects PQ at A and B.
(c) Taking A and B as centres and radius more than half of AB, draw two arcs intersecting each other at R.
(d) Join OR. Thus, ∠QOR = ∠POQ = 90°.
(e) Draw \(\overline{\mathrm{OD}}\) the bisector of ∠POR.
Thus, ∠QOD is required angle of 135°.
(f) Now, draw \(\overline{\mathrm{OE}}\) as the bisector of ∠QOD.
Thus, ∠QOE = ∠DOE =67\(\frac { 1 }{ 2 }\)°

Question 8.
Draw an angle of 70°. Make a copy of it using only a straight edge and compasses.
Answer:
Steps of construction:
Step I: Draw a line 1 and mark a point O on it.
Step II: Using a protractor construct ∠AOB = 70°.
Step III: With centre O and a suitable radius, draw an arc which intersects \(\overline{\mathrm{OA}}\) and \(\overline{\mathrm{OB}}\) at E and F respectively.

Step IV: Draw a ray \(\overline{\mathrm{PQ}}\).

Step V: Keeping the same radius and centre P, draw an arc intersecting \(\overline{\mathrm{PQ}}\) at R.
Step VI: With centre R and radius equal to EF, draw an arc intersecting the previous arc at S.
Step VII: Join PS and produce it.

Question 9.
Draw an angle of 40° Copy its supplementary angle.
Answer:
Steps of construction:
Step I: (a) By using protractor draw ∠AOB = 40°
∠COF is the supplementary angle.
Step II: With centre O and a convenient radius, draw an arc which intersects \(\overline{\mathrm{OC}}\) and \(\overline{\mathrm{OB}}\) and E and F respectively.

Step III: Draw a ray \(\overline{\mathrm{OC}}\).

Step IV: With centre Q and same radius, draw an arc intersecting \(\overline{\mathrm{OC}}\) at L.
Step V: With centre L and radius equal to EF draw an arc which intersects the previous arc at S.
Step VI: Join QS and produce it.
Thus, ZPQS is the copy of the supplementary angle ZCOB.