CBSE Class 8

In this page, we are providing Coal and Petroleum Class 8 Extra Questions and Answers Science Chapter 5 pdf download. NCERT Extra Questions for Class 8 Science Chapter 5 Coal and Petroleum will help to score more marks in your CBSE Board Exams.

Class 8 Science Chapter 5 Extra Questions and Answers Coal and Petroleum

Extra Questions for Class 8 Science Chapter 5 Coal and Petroleum with Answers Solutions

Coal and Petroleum Class 8 Extra Questions Very Short Answer Type

Question 1.
Name some renewable sources of energy.
Answer:
Water, wind, solar.

Question 2.
Give some examples of fossil fuels.
Answer:
Coal, petroleum, natural gas.

Question 3.
Name the elements present in coal.
Answer:
Carbon, oxygen and sulphur.

Question 4.
Which are the two main techniques of mining?
Answer:
Surface mining and underground mining.

Question 5.
List four varieties of coal.
Answer:
Peat, lignite, bituminous, anthracite.

Question 6.
Name the process of conversion of wood into coal.
Answer:
Carbonisation

Question 7.
Mention the temperature at which destructive distillation is done.
Answer:
1000°C

Question 8.
When the crude oil is referred to be ‘sweet’?
Answer:
If the sulphur content is low.

Question 9.
Name the process of conversion of kerogen into gaseous hydrocarbons.
Answer:
Catagenesis

Question 10.
Name the country which is the leading producer of petroleum.
Answer:
Saudi Arabia

Question 11.
Name the gas that occurs over petroleum in reservoirs deep inside the earth.
Answer:
Natural gas

Question 12.
Expand PCRA.
Answer:
Petroleum Conservation Research Association.

Question 13.
Name two fractions of petroleum which are used as fuel.
Answer:
Petrol and diesel

Question 14.
What kind of pollution is caused by the burning of fossil fuels?
Answer:
Air pollution

Question 15.
Write the full form of LPG.
Answer:
Liquefied Petroleum Gas.

Question 16.
Which gas is produced when coal is burnt in air?
Answer:
Carbon dioxide

Question 17.
Can we use all our natural resources forever?
Answer:
No

Question 18.
What is the purest form of carbon?
Answer:
Coke

Question 19.
Where and when was the first oil well drilled?
Answer:
Pennsylvania, USA in 1859.

Question 20.
Name the places where natural gas is found in our country.
Answer:
Tripura, Rajasthan, Krishna Godavari Delta, Maharashtra, etc.

Coal and Petroleum Class 8 Extra Questions Short Answer Type

Question 1.
What is fuel?
Answer:
Anything that burns to produce energy in an efficient manner is called a fuel.

Question 2.
Define fossil fuels. Give examples.
Answer:
Natural fuels that are made up by burial of living organisms under deep down the earth for over a long period of time, are called fossil fuels. For example, coal, petroleum, natural gas.

Question 3.
What is coal? Write its two uses.
Answer:
Coal is a hard, black combustible substance that mainly contains carbon.
Uses:

• It is used as a fuel in homes and industry.
• It is used as a fuel at Thermal Power Plants for generating electricity.

Question 4.
Give a brief description about peat.
Answer:
Peat is the most inferior and softest form of coal. Its carbon content is very low. It has a large amount of moisture and is not much suitable to be used as fuel. Its carbon content is 20 – 25%.

Question 5.
Name three constituents of petroleum and write their uses also.
Answer:
The three constituents of petroleum are:
(a) petrol
(b) paraffin wax
(c) diesel
Uses:
(a) Petrol: It is used as a motor fuel and for dry cleaning.
(b) Paraffin wax: It is used for making ointments, candles, vaseline, etc.
(c) Diesel: It is used as a fuel for heavy motor vehicles and electric generators.

Question 6.
Explain about coal tar.
Answer:
It is produced when the gases are evolved due to heating of coal in water. It is a black-coloured, thick, viscous liquid. It has a pungent smell. It is itself a mixture of many compounds. We can get benzene, toluene, napthalene, phenol, etc., from coal tar.

Question 7.
Name two products that you obtain from the destructive distillation of coal. What is the residue left in’ this process? Give one main use of this residue.
Answer:
The two important products obtained from the destructive distillation of coal are: Coal gas and coal tar. The residue left in this process is coke. Coke is used mainly as a reducing agent in the extraction of metals.

Question 8.
Where do we get coal and how is it formed?
Answer:
We get coal deep in the earth’s crust in coal mines. It is formed by the slow decomposition of dead trees and other vegetable matter buried deep under the earth’s crust under high pressure and temperature.

Question 9.
Define the term ‘petrochemicals’.
Answer:
Petrochemicals are the substances obtained from petroleum and natural gas. They are used in the manufacture of detergents, fibres, polythene, etc.

Question 10.
What is CNG? What are its uses?
Answer:
CNG is short form of Compressed Natural Gas. Natural gas is stored under high pressure as CNG. CNG is used for power generation. It is now being used as a fuel for transport vehicles because it is less polluting. It is a cleaner fuel.

Coal and Petroleum Class 8 Extra Questions Long Answer Type

Question 1.
Explain about the varieties of coal.
Answer:
Depending upon the amount of carbon content, coal may be of four types:

• Peat: This is the most inferior and softest form of coal. Its carbon content is very low. It has a large amount of moisture and is not much suitable to be used as fuel.
• Lignite: Lignite is comparatively harder than peat, but still is very soft. Its carbon content is more than that of peat.
• Bituminous: Its carbon content is higher, as it is free from moisture and other impurities.
• Anthracite: This is the highest grade coal. This is also known as hard coal. It has maximum amount of carbon. It produces a very little smoke.

Question 2.
The burning of fossil fuels causes air pollution. Explain.
Answer:
The burning of fossil fuels causes a lot of air pollution.

The burning of coal produces gases like carbon dioxide, carbon monoxide, sulphur dioxide, etc., which can lead to undesirable changes in climate due to increase greenhouse effect.

The major air pollutants produced by the burning of petrol in automobiles are carbon monoxide, sulphur dioxide, unbumt hydrocarbons, etc. These pollutants are harmful for human beings and living organisms which causes breathing problems and skin diseases.

Question 3.
Write a short note on petroleum.
Answer:
Petroleum is the liquid form of fuel. It is also known as crude oil and found trapped between the layers of impervious rocks under the ground. It is a natural resource, which formed by the dead plants and animals in the sea. It is a dark coloured viscous liquid and like all other oils, it is lighter than water. It is a mixture of different hydrocarbons. It undergoes fractional distillation to yield petrol, kerosene, diesel and other chemicals used in manufacture of plastics.

Question 4.
How is the energy useful to us? Explain.
Answer:
We need energy in almost every field of our life. Without energy our life is impossible.
Some of the uses of energy are:

• We need energy of fuels to generate electricity and to run vehicles.
• We need energy to run our electrical appliances like refrigerator, TV, radio, computer, etc.
• We need energy at construction sites to construct houses, buildings, etc.
• We need energy to cook our food and other domestic use.
• We need energy (petrochemicals) for manufacturing fibres, plastics, paints, cosmetics, etc.
• All the factories, industries, agricultural devices depend on power supply to run the machines.

Question 5.
List the steps to conserve the resources.
Answer:
As we know, we all are dependent on the resources. But we should keep in mind that resources are limited in nature. If we misuse it, our future generation will have no resources. This is an alarming situation.
We can take following steps:

• We shbuld cook our food on low flame.
• Devices that consume less energy like CFLs and LED lights should be preferred.
• We should take care not to waste electricity.
• We should cover our cooking vessels while cooking.
• Instead of use of individual vehicles, use of public transport should be encouraged.
• Solar or tidal energy should be developed and encouraged.
• Dams should be use to generate electricity instead of burning coal or petroleum.
• Public awareness programmes should be conducted.

Coal and Petroleum Class 8 Extra Questions HOTS

Question 1.
You are provided with a mixture of petroleum and water. How will you separate the two?
Answer:
Allow to stand the mixture of petroleum and water undisturbed for some time. The top layer will be consisted of petroleum which can be separated from water by decantation.

Question 2.
Differentiate between coke and coal.
Answer:

Question 3.
None of the fuels is clean fuel. Comment.
Answer:
On burning, every fuel releases atleast CO₂ which causes greenhouse effect. Thus none of the fuels are clean.

Question 4.
Can forests help reduce the pollution caused by burning of fossil fuels? How?
Answer:
Not all, but yes it reduces some of the pollution like carbon dioxide emitted during burning of fossil fuels.

Question 5.
What other source of energy may be used to drive vehicles?
Answer:
Biodiesel, ethanol, solar energy.

Coal and Petroleum Class 8 Extra Questions Value Based (VBQs)

Question 1.
Radhey prefers to go to school by pooling car. On other occasions he like to opt for public transport rather than private transport. For short distances, he walks or uses bicycle.
(a) What are the benefits of carpooling?
(b) Which mean of transport do you think is best for short distances?
(c) How on our end we can reduce the consumption of fossil fuels?
(d) What values of Radhey are shown here?
Answer:
(a)

• Cost effective
• Reduces pollution
• Reduces traffic on roads
• Saves fossil fuels

(b) Bicycle
(c)

• By reducing use of plastics as these are products of fossil fuels.
• By consuming electrical energy judiciously as most of the electricity comes from burning coal.
• By carpooling. As car uses petrol or diesel a form of fossil fuel.
• Switching engine off at red lights.

(d) Radhey is eco-friendly, environmentally conscious and works judiciously.

Question 2.
There was an essay-writing competition on ‘How to Reduce your Carbon Footprint’ in Satish’s school. Satish enquired his best on this topic to his elders and searched internet. He got the first prize in the competition.
(a) What do you understand by the term ‘Carbon Footprint’?
(b) Suggest ways to reduce your carbon footprint.
(c) What values of Satish are shown here?
Answer:
(a) The total amount of greenhouse gases produced by an individual, organisation or event is known as ‘Carbon Footprint’.
(b)

• Follow 3R’s, i.e., – reduce, reuse and recycle.
• Use public transport and carpool.
• Avoid traffic.
• Plant trees.
• Use energy efficient appliances.

(c) Satish is inquisitive, intelligent, hard working and sincere boy.

In this page, we are providing Materials: Metals and Non-Metals Class 8 Extra Questions and Answers Science Chapter 4 pdf download. NCERT Extra Questions for Class 8 Science Chapter 4 Materials: Metals and Non-Metals will help to score more marks in your CBSE Board Exams.

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

Extra Questions for Class 8 Science Chapter 4 Materials: Metals and Non-Metals with Answers Solutions

Materials: Metals and Non-Metals Class 8 Extra Questions Very Short Answer Type

Question 1.
Name some common metals.
Answer:
Copper, aluminium, iron, silver, gold, etc.

Question 2.
Name some common non-metals.
Answer:
Hydrogen, oxygen, carbon, sulphur, phosphorus, etc.

Question 3.
Give examples of metalloids.
Answer:
Antimony, arsenic, silicon, boron, etc.

Question 4.
Name the property due to which metals shine.
Answer:
Lustre

Question 5.
Name two metals which are soft enough to be cut.
Answer:
Potassium and sodium

Question 6.
Name the property due to which metals can be beaten into thin sheets.
Answer:
Malleability

Question 7.
Which non-metal does conduct heat and electricity?
Answer:
Carbon

Question 8.
Name the property due to which metals can be drawn into wires.
Answer:
Ductility

Question 9.
Name the metal and non-metal which occur in liquid state.
Answer:
Mercury (metal), bromine (non-metal).

Question 10.
Due to which property a bell rings?
Answer:
Sonority

Question 11.
Generally, non-metals are non-lustrous. Name one non-metal which is lustrous.
Answer:
Iodine

Question 12.
State the property of non-metals due to which phosphorus is kept in water.
Answer:
Non-metals do not react with water.

Question 13.
Why some metals displace other metals from their solution?
Answer:
Because of being more reactive than the metals which they displace.

Question 14.
Which metal is used for wrapping food items?
Answer:
Aluminium

Question 15.
Which metal is more reactive: Iron or zinc?
Answer:
Zinc

Question 16.
Which metal is less reactive: Copper or zinc?
Answer:
Copper

Question 17.
Name one metal which does not react with dilute hydrochloric acid.
Answer:
Copper

Question 18.
Whose oxides are basic in nature: Metal or non-metal?
Answer:
Metal

Question 19.
Whose oxides are acidic: Metal or non-metal?
Answer:
Non-metal

Question 20.
Name two metals which do not react with oxygen even at high temperature.
Answer:
Gold and silver

Question 21.
Classify the following into metals and non-metals:
Copper, iron, graphite, sulphur, aluminium, oxygen
Answer:
Metals: Copper, iron, aluminium
Non-metals: Graphite, sulphur, oxygen

Question 22.
Name two physical properties of metals.
Answer:
Malleability and sonority

Question 23.
What happens when metals react with oxygen?
Answer:
Metal oxides are formed.

Question 24.
What happens when magnesium is burnt in air?
Answer:
Magnesium burns with a white dazzling flame and a white powdery magnesium oxide is formed.

Question 25.
What happens when metals react with water?
Answer:
Metals produce their hydroxides or oxides and hydrogen.

Materials: Metals and Non-Metals Class 8 Extra Questions Short Answer Type

Question 1.
What is a metal?
Answer:
Substances having characteristic properties like malleability, ductility, sonority, conductivity, lustre, – and solidness are called metals. For example, aluminium, copper, zinc, iron, etc.

Question 2.
What are non-metals?
Answer:
Substances which are soft and dull, i.e., non-lustrous, non-sonorous, non-ductile, non-malleable and poor conductor of heat and electricity are called non-metals. For example, oxygen, hydrogen, sulphur, etc.

Question 3.
Mention the physical properties of metals.
Answer:
Physical properties of metals are:

• Malleable
• Lustre
• Sonorous
• Ductile
• Solid
• Good conductor of heat and electricity

Question 4.
What are the physical properties of non-metals?
Answer:
The physical properties of non-metals are:

• Non-malleable
• Non-sonorous
• Non-lustrous, i.e., dull in appearance
• Non-ductile
• Poor conductor of heat and electricity

Question 5.
Explain the term ‘malleability’ with suitable examples.
Answer:
Malleability is the property of metals due to which they can be beaten into thin sheets. For example, if we beat or hammer any metal like aluminium, zinc, iron, copper, etc., it become longer and larger but does not break. Thin sheets can be obtained by this process.

Question 6.
What is ductility? Explain with examples.
Answer:
Ductility is one of the properties of metals due to which they can be drawn into wires. For example, aluminium and copper are drawn into wires and used for electrical and different purposes.

Question 7.
Why aluminium is used for wrapping of food items?
Answer:
Aluminium is a metal and hence possesses malleability property. It can be beaten into thin sheets and can be folded into any shape. It is cheaper than other malleable metals and does not react with food items. That is why it is used as wrapping materials for food items.

Question 8.
Why metals are used in ringing bells?
Answer:
Metals have sonority. Due to this property, they can produce ringing sounds. That is why metals are used in ringing bells.

Question 9.
What are the differences between metals and non-metals? Explain on the basis of their physical properties.
Answer:

• Metals are malleable and give thin sheets after hammering whereas non-metals are brittle and give no sheets.
• Metals are ductile and can be drawn into wires whereas non-metals are non-ductile and can’t be drawn into wires.
• Metals are sonorous and used in ringing bells whereas non-metals are non-sonorous and cannot be used in ringing bells.
• Metals are good conductors of heat and electricity while non-metals are poor conductors.

Question 10.
What happen when a copper vessel is exposed to moist air for long? Also write the equation.
Answer:
When a copper vessel is exposed to moist air for long, it acquires a dull green coating. This green material is a mixture of copper hydroxide [Cu(OH)₂] and copper carbonate (CuCO₃). The reaction is as follows:

Question 11.
What happens when a magnesium ribbon is heated in presence of air?
Answer:
When a magnesium ribbon is heated in presence of air, it burns with a white dazzling flame and a white powdery magnesium oxide is formed.

Question 12.
How do metals and non-metals react with water?
Answer:
Metals produce their hydroxides or oxides and hydrogen when they react with water. Sodium and potassium react with cold water along with the production of a large amount of heat. Magnesium react with boiling water and iron with steam. Gold, silver and platinum do not react with water. Non-metals do not react with water.

Question 13.
With the help of equations, explain the reaction of non-metals with oxygen.
Answer:
Non-metals react with oxygen to form acidic oxides. But most of the non-metals reacts with oxygen on ignition.
The equations follow as:

Question 14.
How do metals and non-metals react with acids?
Answer:
Metals react with acids to form respective salts along with evolution of hydrogen gas that burns with a pop sound. The equation are as follows:

There are some metals like copper, silver, gold and platinum that do not liberate hydrogen with acids. Generally, non-metals do not react with acids.

Question 15.
How do metals and non-metals react with bases?
Answer:
Most of the metals do not react with bases. However, some metals like aluminium, lead and zinc react with strong bases like sodium hydroxide (NaOH) to make complex salts and hydrogen.
Generally, non-metals do not react with bases. Sometimes some complex reactions take place between non-metals and bases.

Question 16.
What is a displacement reaction? Give one example.
Answer:
A chemical reaction in which a more reactive metal displaces a less reactive metal is called displacement , reaction. For example, when zinc (Zn) reacts with copper sulphate (CuSO₂), zinc replaces copper being it more reactive than copper. The equation is

Materials: Metals and Non-Metals Class 8 Extra Questions Long Answer Type

Question 1.
Distinguish between metals and non-metals on the basis of their physical properties.
or
Compare the physical properties of metals and non-metals.
Answer:
Difference between metals and non-metals on the basis of their physical properties.

Question 2.
Distinguish between metals and non-metals on the basis of their chemical properties.
or
Compare between metals and non-metals on the basis of their chemical properties.
Answer:
Difference between metals and non-metals on the basis of their chemical properties.

Question 3.
Explain chemical properties of metals with examples.
Answer:
(i) Reaction with oxygen or air: Metals react with oxygen to form basic oxides.
Some metals like potassium and sodium react vigorously with oxygen. For example,

Some noble metals like gold, silver and platinum do not react with oxygen. Iron (Fe) and copper (Cu) get rusted when react in presence of oxygen and water (moist air).

(ii) Reaction with water: Metals react with water to form their oxides or hydroxides. Gold, silver and platinum do not react with water. Some metals like sodium, potassium react vigorously with water. For example,

(iii) Reaction with acids: Metals react with acid to form their salts followed by evolution of hydrogen gas. For example,

Some metals like gold, copper, silver, etc., do not liberate hydrogen gas with acids.

(iv) Reaction with bases: Most of the metals do not react with bases. However some metals like aluminium, zinc and lead react with strong bases like sodium hydroxide to make complex salts and produce hydrogen.

(v) Displacement reactions: More reactive metals displace less reactive metals. For example,

In the above reactions, zinc (Zn) and magnesium (Mg) are more reactive than copper (Cu), hence they replace copper from its solution.

Question 4.
Explain with suitable examples the chemical properties of non-metals.
Answer:
Reaction with oxygen: Non-metals react with oxygen to form acidic oxides. But most of them do this on ignition. For example,

They form negative ions and are good oxidising agents.
Reaction with water: Non-metals do not react with water.
Reaction with acids and bases: Generally, non-metals do not react with acids and bases. How¬ever, sometimes some complex reactions take place between non-metals and bases.

Question 5.
What are main uses of metals?
or
How are metals useful to us?
Answer:
Metals are very useful to us in many ways. For example,
(i) Due to their thermal and electrical conductivity, metals are use to make utensils, cooking vessels, wires and appliances. For example, copper and aluminium are mainly used for these purposes.

(ii) Metals like iron and steel are used in various tools, machinery, pipes, rods, sheets, doors, windows, construction works like bridges, roads, buildings, etc.

(iii) Aluminium is used as packaging and wrapping materials. It is also used in aircrafts and automobiles, etc.

(iv) Metals like gold, silver and platinum are used to make jewellery and other decorating items.

(v) Zinc is used in galvanisation and dry cell and chromium in electroplating.

(vi) Lead is used in making electrodes and batteries.

Question 6.
What are the main uses of non-metals?
or
How are non-metals useful to us?
Answer:
Like metals, non-metals also play an important role in our lives. They help us in many ways. For example,
(i) We breathe oxygen which is the basis of life of all living things including human beings. Without it, no living beings can exist alive on this earth.

(ii) CO₂ which is a non-metal oxide is essential for plants to carry out photosynthesis.

(iii) Non-metals like nitrogen and phosphorus are used in fertilisers for better yield of plant. Phosphorus is used in manufacturing of matchsticks and fireworks.

(iv) Non-metal like iodine is used in the purple coloured solution applied on wounds. Sulphur is also used in preparing skin medicines and making ointment due to its fungicidal properties.

(v) Non-metal like chlorine is used in water purification process. Due to its bleaching properties it is used to make bleaching powder.

(vi) Carbon, a non-metal, is used in most of the fuels.

Question 7.
What is reactivity series? Suggest an activity to arrange sodium, magnesium and copper in the order of their decreasing reactivity.
Answer:
Reactivity series is an arrangement of metals in decreasing order of their reactivity from highest to lowest. The metals occupying the higher positions in the activity series are more reactive in displacing the other metals lying below it from the solutions of their salts.

The activity series is a useful guide for predicting the products of metal displacement reactions. For example, placing a strip of zinc metal in a copper (II) sulphate solution will produce metallic copper and zinc sulphate, since zinc is above copper on the series.

A trip of copper placed into a zinc sulphate solution will not produce an appreciable reaction, because copper is below zinc on the series and can’t displace zinc ions from solution.

Activity to arrange sodium, magnesium and copper in the order of their decreasing reactivity:
(i) Take a pinch of sodium with a forceps and place in a beaker containing water. You will notice that sodium reacts vigorously.

(ii) Take a small piece of magnesium ribbon and add warm water to it. Magnesium reacts with warm water to form magnesium oxide and hydrogen gas. Magnesium reacts very slowly with cold water.

(iii) Take small pieces of copper turnings and add warm water to it. It doesn’t react with warm water also.

Hence, increasing order of reactivity is Na > Mg> Cu.

Materials: Metals and Non-Metals Class 8 Extra Questions HOTS

Question 1.
Why does calcium float in water?
Answer:
The hydrogen gas formed on adding calcium to water sticks to the surface of calcium solid and make it float in water.

Question 2.
Zinc sulphate forms a colourless solution in water. Will you observe any colour on adding copper turning in it?
Answer:
No, because copper is less reactive than zinc and will not be able to displace zinc from its salt solution

Question 3.
A doctor prescribed a tablet to a patient suffering from iron deficiency. The tablet does not look like iron. Explain.
Answer:
The tablet is not made of iron metal, instead it contains a salt of iron.

Question 4.
Ram stored copper sulphate solution in a container made of iron. He observed certain changes after few hours. Can you tell what changes did he observed?
Answer:
Blue colour solution of copper sulphate has changed to green colour of ferrous sulphate. The iron container was found to be corroded from many places. A red powdery deposit of copper sulphate was found on the iron container.

Question 5.
Imagine that gold is reactive like copper. Will it be still wanted? Why or why not?
Answer:
If gold becomes reactive like copper then its use in ornaments will decline. This is because due to its increase reactivity it will lose its shine frequently which in turn will reduce its demand.

Materials: Metals and Non-Metals Class 8 Extra Questions Value Based (VBQs)

Question 1.
Gold is a very precious metal. Pure gold is very soft and is thus not suitable for making jewellery. It is alloyed with either silver or copper to make it hard. But some jewellers mix a large quantity of copper and silver in gold to earn more profit.

(a) What precautions should you take while purchasing gold jewellery?
(b) What standard you must see on gold ornaments?
(c) What value of shopkeeper’s are shown here?
Answer:
(a) We must see the carat of gold jewellery, current price and BIS hallmark on it.
(b) BIS hallmark.
(c) Some shopkeeper’s are greedy, mean, cheater and money minder.

Question 2.
Mercury is largely used in thermometers to measure the temperature. It is a very dangerous metal as its density is very high. If it get into the food chain, it leads to mercury poisoning.
(a) What two precautions you must take while handling equipments containing mercury?
(b) Why mercury is used in thermometers?
(c) Can you suggest other alternatives to mercury thermometers?
Answer:
(a)

• We must handle the equipments carefully and firmly.
• If there is a mercury spill, we must leave the area immediately and inform our parents or teachers.

(b) Mercury is a good conductor of heat. Hence, the slightest change in temperature i° otable when it is used in a thermometer.
(c) Digital thermometer and spirit thermometer.

In this page, we are providing Synthetic Fibres and Plastics Class 8 Extra Questions and Answers Science Chapter 3 pdf download. NCERT Extra Questions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics with Answers will help to score more marks in your CBSE Board Exams.

Class 8 Science Chapter 3 Extra Questions and Answers Synthetic Fibres and Plastics

Extra Questions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics with Answers Solutions

Synthetic Fibres and Plastics Class 8 Extra Questions Very Short Answer Type

Question 1.
Name a natural fibre.
Answer:
Cotton

Question 2.
Name the basic component of animal fibres.
Answer:
Protein

Question 3.
Name some artificial fibres.
Answer:
Nylon, terylene, PET, acrylic, teflon, etc.

Question 4.
Which fibre is known as artificial silk?
Answer:
Rayon

Question 5.
In which country was rayon first time synthesised?
Answer:
England

Question 6.
Name the first fully synthetic fibre.
Answer:
Nylon

Question 7.
Name the largest producer unit of rayon in the world.
Answer:
Grasim India

Question 8.
Name a common variety of polyester.
Answer:
Terylene

Question 9.
What is ester?
Answer:
Ester is sweet-smelling compound.

Question 10.
Name some objects made of plastics.
Answer:
Containers, buckets, bottles, chairs, baskets, etc.

Question 11.
What is polythene?
Answer:
Polythene is a polymer of ethene.

Question 12.
Give some examples of thermoplastics.
Answer:
Polythene and polyvinyl chloride.

Question 13.
Give some examples of thermosetting plastics.
Answer:
Bakelite and melamine.

Question 14.
What is the full form of PVC?
Answer:
Polyvinyl Chloride

Question 15.
What is 4R’s?
Answer:
4R’s stands for Redue, Reuse, Recycle and Recover.

Question 16.
Whether cotton cloth a biodegradable or non-biodegradable?
Answer:
Biodegradable

Question 17.
Name the form of polyester which is replacing materials like glass and used for making bottles and jars.
Answer:
PET (Polyethylene Terephthalate)

Question 18.
Which of two is thermosetting plastic—PVC or bakelite?
Answer:
Bakelite

Question 19.
Name a synthetic fibre which is polyamide.
Answer:
Nylon

Question 20.
Give the name of a plastic used for making fibres.
Answer:
Nylon

Synthetic Fibres and Plastics Class 8 Extra Questions Short Answer Type

Question 1.
What are polymers?
Answer:
Polymers are compounds that are made up of same, small repeating units, joined together through bonds in a linear pattern.

Question 2.
What is cellulose?
Answer:
Cellulose is a polymer made up of large number of glucose units.

Question 3.
List the two ways in which synthetic fibres can be synthesised.
Answer:
Synthetic fibres may be synthesised by two ways:

• By regenerating them from natural fibres, like in rayon.
• By using entirely chemicals and chemical reactions, like in nylon.

Question 4.
What is rayon?
Answer:
Rayon is a man-made fibre which is produced by the chemical processing of wood pulp, i.e., a natural substance.

Question 5.
List two uses of rayon.
Answer:
The two uses of rayon are:

• It is used to make apparels like shirts, blouses, etc.
• It is used to make furnishings and upholstery.

Question 6.
List any two properties of rayon.
Answer:
The two properties of rayon are:

• Rayon is a versatile fibre.
• It can be dyed in different colours.

Question 7.
Draw a diagram to show the:
(a) linear arrangement of units in plastic.
(b) cross-linked arrangement of units in plastic.
Answer:

(a) Linear
(b) Cross-linked arrangement

Question 8.
Write some advantages of synthetic fibres.
Answer:
Advantages of synthetic fibres are:

• Synthetic fibres are strong and durable.
• They do not shrink.
• They are moth and insect resistant.

Question 9.
What are plastics?
Answer:
Plastics are those substances which are mostly synthetic in nature, obtained mainly from petrochemi¬cal sources and can be moulded into different shapes.

Question 10.
What is plasticity?
Answer:
Plasticity is the property of materials by which they can be moulded into any shape.

Question 11.
What are thermosetting plastics?
Answer:
Thermosetting plastics are those which when moulded once, cannot be softened again and lose their plasticity.

Question 12.
List any three properties of plastics.
Answer:
The three properties of plastics are:

• They are non-corrosive in nature.
• They are light in weight and durable.
• They do not conduct heat.

Question 13.
What are the uses of polyester?
Answer:
The uses of polyester are:

• It is used in making home furnishings and apparels.
• Polyester is used for finishing on guitars and pianos.

Question 14.
Why is it advised not to wear synthetic clothes while working in a laboratory or working with fire in the kitchen?
Answer:
The synthetic fibres melt on heating. This is actually a disadvantage with synthetic fibres. If the cloth catches fire it can be very disastrous. The fabric melts and sticks to the body of the person wearing it. It is therefore advised not to wear synthetic clothes while working in a laboratory or working with fire in the kitchen.

Question 15.
Write some properties and uses of melamine.
Answer:
Melamine is a versatile material. It resists fire and can tolerate heat better than other plastics. It is used for making floor tiles, kitchenware and fabrics which resist fire.

Synthetic Fibres and Plastics Class 8 Extra Questions Long Answer Type

Question 1.
Describe about nylon. Write its uses and properties.
Answer:
Nylon is the strongest amongst all the synthetic fibres. It is fully synthetic polymer which is prepared from coal, water and air. It is a polymer of amides. It was made in 1931 for the first time. It was used as a supplement of silk when silk got deficient during World War II for many military applications.

Uses of Nylon

• Nylon is used in toothbrushes, combs, etc.
• It is used to make parachutes, tents, ropes, etc.
• It is used to make socks and stockings as it is elastic.
• It is widely used for making clothes, carpets, etc.

Properties of Nylon

• It melts on heating.
• It absorbs less water.
• It is resistant to moths and fungi.
• It has high tensile strength.
• It is durable.

Question 2.
Write the advantages of synthetic fibres.
Answer:
Synthetic fibres has many advantages as compared to natural fibres.
Some of them are as follows:

• They are very strong and durable.
• They are cheaper in cost as compared to natural fibres.
• They absorb less water and are quick to dry.
• They do not shrink.
• They are very useful for saving our trees and animals as they are made up of chemicals.
• They are moth and insect resistant.

Question 3.
List the common varieties of polyester. Also mention the natural fibres which are used for blending to enhance their properties.
Answer:
Polyester could be blended with natural fibres to enhance its properties.
The common varieties of polyester are:

• PET (Polyethylene terephthalate)
• Terrycot: It is made by blending polyester and cotton.
• Terrysilk: It is made by blending polyester said silk.
• Terrywool: It is made by blending polyester and wool.

Question 4.
Explain the properties of plastics.
Answer:
Plastics are those substances which are mostly synthetic in nature.
Following are the properties of plastics:

• Plastics are non-corrosive in nature, i.e., they do not react easily with air and water. They are unaffected by most of the chemicals in normal conditions.
• Plastics are the bad conductor of heat. They do not get heated up like metals.
• Plastics are non-biodegradable, i.e., they do not get decomposed by microorganisms.
• Plastics are very durable.

Question 5.
‘Plastics are hazard to environment’. Explain this statement.
Answer:
Yes, plastics are hazard to environment. They make versatile materials but are very dangerous to the environment. Plastics are non-biodegradable in nature. It takes more than 100 years to decompose. If use of plastics are not reduced, our earth would turn into a big garbage bin.

The major problems due to plastics are:

• If plastics are burnt, they evolve poisonous gases. These gases destroys the ozone layer of the earth and also pollute the environment.
• If the plastics are disposed in drains, they choke the drains causing waterlogging.
• If these plastics are swallowed by the innocent animals along with their food, they harm their di-gestive system which leads to their death.
• They are manufactured by the consumption of a large amount of petroleum.

Question 8.
List the strategies for plastic waste management.
Answer:
Some of the strategies for plastic waste management are:

• We should use paper bags and jute bags instead of using plastic bags.
• The government should ban the use of plastic bags.
• Plastics should be recycled to make other useful products which do not harm the environment.
• We should use a special garbage bins to dispose plastic wastes.
• We should not throw plastic wastes in water bodies.
• Practicing 4R’s principle, i.e., Reuse, Recycle, Reduce and Recover should be encouraged.

Synthetic Fibres and Plastics Class 8 Extra Questions HOTS

Question 1.
Cotton is a natural polymer. What is its chemical name?
Answer:
Cellulose.

Question 2.
Why plastic items are available in all possible shapes and sizes?
Answer:
Plastics can be moulded to any shape. So they are available in all possible shapes and sizes.

Question 3.
What nature of plastics makes them a good storage containers for most of the articles?
Answer:
Plastics are non-reactive.

Question 4.
A lady went to the market to buy a blanket. The shopkeeper showed her blankets made of acrylic fibres as well as made of wool. She preferred to buy an acrylic blanket. Can you guess why?
Answer:
Blanket made of acrylic is cheap, durable, light in weight, available in variety of colours and provide the same warmth as that of wool.

Question 5.
Is using plastics for storing food safe?
Answer:
Though storing and carrying food in plastic container is more efficient. But chemicals used for manufacturing plastics leeches out into the food and contaminates it. Though it is in very small amount but continuous use of it is exposing our body to harmful and poisonous chemicals.

Synthetic Fibres and Plastics Class 8 Extra Questions Value Based (VBQs)

Question 1.
Riya’s father got a transfer to another place. While sorting out the things Riya found many of her clothes of various fabrics were not fitting her or worn out. She thought of burning them to get rid of them. But her friend Shweta suggested to donate it to some charity house so that it can be reused.

(a) What are the two main types of fibres?
(b) Which fabrics are known to be skin friendly? Why?
(c) Why we should not burn synthetic clothes?
(d) Why synthetic clothes are famous than natural fabrics?
(e) What values of Riya and Shweta are shown here?
Answer:
(a) Two main types of fibres are natural and man-made fibres.
(b) Natural fabrics are known to be skin friendly because they absorb moisture and do not contain chemicals as that of synthetic fibres which may cause skin irritation.
(c) Synthetic clothes emits poisonous gases on burning.
(d) Synthetic clothes are famous than natural clothes because they are light, durable, cheaper, easy to maintain, moth resistant and available in various colours.
(e) Riya is ignorant and non-ecofriendly whereas Shweta is insightful and eco-friendly.

Question 2.
Piku is very fond of art and craft. She decided to make some items like pen keeper, purses, toys, etc., using old fabrics and plastics. She donated these in a charity.

(a) Is it practical to say completely ‘NO’ to plastics?
(b) How can we reuse any plastic items?
(c) What value of Piku is shown here?
Answer:
(a) No, it is not at all practical to say completely ‘NO’ to plastics because nowadays plastics are insepa-rable part of our daily life.
(b) We can reuse plastic bags for storing dry things. We can reuse plastic bottles for storing dry food grains or a pen keeper, etc.
(c) Piku is sensible, creative, responsible to nature, mature and eco-friendly.

In this page, we are providing Microorganisms: Friend and Foe Class 8 Extra Questions and Answers Science Chapter 2 pdf download. NCERT Extra Questions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe will help to score more marks in your CBSE Board Exams.

Class 8 Science Chapter 2 Extra Questions and Answers Crop Microorganisms: Friend and Foe

Extra Questions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe with Answers Solutions

Microorganisms: Friend and Foe Class 8 Extra Questions Very Short Answer Type

Question 1.
Name the groups in which microorganisms are broadly classified.
Answer:
Microorganisms are broadly classified in four groups:

• bacteria
• fungi
• protozoa
• algae

Question 2.
Name the type of microorganism that is smaller than bacteria.
Answer:
Virus

Question 3.
Write the name of a bacterium that helps in the formation of curd.
Answer:
Lactobacillus

Question 4.
Write a use of yeast.
Answer:
Yeast is used in the production of alcohol, wine, beer and other beverages.

Question 5.
What does yeast produce during respiration? ‘
Answer:
Yeast produces carbon dioxide gas during respiration.

Question 6.
What are pathogens? Write another name of pathogens.
Answer:
Disease-causing microorganisms are known as pathogens. They are also called germs.

Question 7.
Define food preservation.
Answer:
Food preservation is the method of preserving food from being spoiled by the microbes.

Question 8.
Write the names of any two antibiotics.
Answer:

• Streptomycin
• Erythromycin

Question 9.
Who discovered the vaccine for small pox?
Answer:
Edward Jenner

Question 10.
What is fermentation?
Answer:
Fermentation is the process of conversion of food into alcohol.

Question 11.
Define refrigeration.
Answer:
The storing of food products at the temperature of 0°C to 5°C is known as refrigeration.

Question 12.
What is vaccine?
Answer:
A substance which is used in the production of immunity against various diseases in the living body is termed as vaccine.

Question 13.
Name any two human diseases caused by viruses.
Answer:

• Measles
• Polio

Question 14.
Name any three common plant diseases.
Answer:
Rust of wheat, citrus canker and wilt

Question 15.
Name a microorganism which helps in nitrogen fixation.
Answer:
Rhizobium

Question 16.
Name a disease caused by food poisoning.
Answer:
Botulism

Question 17.
What is the difference between refrigeration and freezing?
Answer:
In refrigeration, the storing of the food is done at a temperature of 0°C to 5°C, whereas freezing is used to store food at -18°C of temperature.

Question 18.
What is decomposition?
Answer:
Decomposition is the process in which organic materials are broken down into simple inorganic sub-stances by the microorganisms.

Question 19.
Name the two microbes that are involved in the process of decomposition.
Answer:
Bacteria and fungi

Question 20.
Name the first antibiotic discovered.
Answer:
Penicillin

Microorganisms: Friend and Foe Class 8 Extra Questions Short Answer Type

Question 1.
What are microorganisms? Give four examples.
Answer:
Small organisms that cannot be seen through the naked eyes and can only be seen under a microscope are called microorganisms or microbes; e.g., Amoeba, Paramecium, Volvox, Spirogyra, etc.

Question 2.
Classify bacteria on the basis of their shapes.
Answer:
On the basis of their shapes, bacteria are classified into four categories:

• rod-shaped bacteria (bacilli)
• spherical-shaped bacteria (cocci)
• curved-shaped bacteria (vibrios)
• spiral-shaped bacteria (spirilla)

Question 3.
Define communicable diseases. Give some examples.
Answer:
Communicable diseases are microbial diseases that can spread from an infected person to a healthy person through air, water, or other physical contacts; e.g., cholera, chicken pox, tuberculosis, common cold, etc.

Question 4.
Differentiate between viruses and other microorganisms.
Answer:

Question 5.
What do you mean by food spoilage?
Answer:
The process in which food is deteriorated to such extent that it does not remain fit for human consump¬tion is known as food spoilage.

Question 6.
What role does sugar play in the preservation of food?
Answer:
The role of sugar in food preservation is significant. By adding sugar in the food item, we reduce its moisture content and hence, it stops the growth of the microorganisms.

Question 7.
How are carriers harmful to us?
Answer:
Carriers take with them many harmful microorganisms or pathogens. They play a great role in trans¬ferring these pathogens to a healthy person, by sitting on the food items, or directly transferring the pathogens inside the body of a person. Hence they are harmful to us.

Question 8.
What is vaccination?
Answer:
The process of putting a vaccine inside the body of a person in order to produce immunity against some disease is called vaccination.

Question 9.
What do you mean by immunity?
Answer:
Immunity is the ability of a body to develop resistance against diseases.

Question 10.
Give two examples of each of the following types of microorganisms:
(a) Algae (b) Fungi (c) Protozoa
Answer:
(a) Algae – Spirogyra, Chlamydomonas
(b) Fungi – Aspergillus, yeast
(c) Protozoa – Paramecium, Amoeba

Question 11.
What are antibodies?
Answer:
Whenever any harmful disease-causing microorganism enters the human body, the body produces sub¬stances to fight with the entered microbe. These substances are called antibodies.

Question 12.
What is the role of bacteria in increasing the soil fertility?
Answer:
Some bacteria, which are present in the root nodules of leguminous plants or free-living fix the atmospheric nitrogen in the soil which is ultimately used up by the plants. Hence they increase the fertility of the soil. For example, Rhizobium, Azotobacter, Azospirillum, etc.

Question 13.
Define Ohmic heating.
Answer:
Ohmic heating is the process in which electric current of high voltage is passed through the food items to kill the microbes that cause the spoilage of food.

Question 14.
What is sterilisation?
Answer:
The process of killing all the microorganisms above the temperature of 100°C is known as sterilisation. It is one of the widely used methods to preserve food, and is often used for various food items.

Question 15.
What is pasteurisation?
Answer:
Pasteurisation can be defined as the partial sterilisation of foods at a temperature that destroys harmful microorganisms without major changes in the chemical property of the food.

Microorganisms: Friend and Foe Class 8 Extra Questions Long Answer Type

Question 1.
Explain why antibiotics do not work against flu or any infection caused by viruses.
Answer:
Viruses cannot be killed by using antibiotics as their cell pathways are different from that of bacteria. It means taking antibiotics to get rid of flu or any other viral infection is useless, because it does not reduce the strength of the virus, nor does it reduce the duration of the infection. But, however, antibiotic will work if we get attacks of viral infection and bacterial disease at the same time. Even then, it will cure bacterial disease only but not the viral infection.

Question 2.
Mention any three ways through which pathogens are transmitted.
Answer:
Three ways because of which pathogens are transmitted are as follows:
(i) When a person sneezes or coughs, tiny droplets containing a number of disease-causing microorganisms come out of the mouth, and are released in the air. They are transmitted to a healthy person while breathing.

(ii) By making direct contacts with an infected person, pathogens are transferred to a healthy person.

(iii) Carriers of pathogens also help in their transmission. For instance, when a fly sits on animal excreta or garbage, harmful disease-causing microbes stick to its legs. And when this fly sits on the food items, pathogens get transferred to them. This contaminated food items cause serious diseases when it is eaten by a healthy person.

Question 3.
Explain canning.
Answer:
Canning is a process used for food preservation. Heat, at a certain temperature and for a limited period of time, is used to kill the harmful microorganisms as well as enzymes. This method also involves the removal of oxygen gas, and to avoid post-process contamination by airtight sealing of food items.

Question 4.
Explain how malaria is transmitted to humans.
Answer:
A protozoan called Plasmodium is responsible for malaria. It lives in the liver and blood of the person who has been infected by this disease. A female Anopheles mosquito when sucks blood from the infected person, Plasmodium along with blood, is taken into its stomach. The Plasmodium, here, multiplies itself and reaches the salivary gland of the mosquito. Now, when this mosquito bites a healthy person, it injects Plasmodium along with saliva to him. The healthy person then gets an attack of malaria. In this way, malaria is transmitted to humans.

Question 5.
Explain various types of bacteria.
Answer:
Bacteria are classified on the basis of their shapes into the following categories:

• Rod-shaped bacteria (bacilli): These are aerobic rod-shaped, spore-producing bacteria. They are often occurring in chain-like formations, and they are found primarily in soil; e.g., Lactobacillus.
• Spherical-shaped bacteria (cocci): They are spherical or nearly spherical bacteria; e.g., Streptococcus.
• Curved-shaped bacteria (vibrios): They are curved-shaped bacteria; e.g., Vibrio.
• Spiral-shaped bacteria (spirilla): They are flagellated, aerobic bacteria, having a spirally twisted rod-like form; e.g., Treponema.

Microorganisms: Friend and Foe Class 8 Extra Questions HOTS

Question 1.
Unscramble the jumbled words underlined in the following statements
(a) Curbossulite is an air-borne disease caused by a bacterium.
(b) Xanrhat is a dangerous bacterial disease.
(c) Yeasts are used in the wine industry because of their property of meronettinaf.
(d) Cells of our body produce santiidobe to fight pathogens.
(e) Aeeessrrwtip are added to food to prevent growth of microorganisms.
Answer:
(a) Tuberculosis
(b) Anthrax
(c) Fermentation
(d) antibodies
(e) Preservatives

Question 2.
What is the difference between Rhizobium and cyanobacteria in the way of fixing nitrogen for the plants?
Answer:
Rhizobium lives in the root nodules of leguminous plants in a symbiotic relationship whereas cyanobacteria lives freely in the soil and fixes nitrogen.

Question 3.
It is always suggested that not to eat anything from street hawkers. Why?
Answer:
Most of street hawkers sells food items in an open area which always get contaminated with the dust and flies carrying germs with them. Such an unhygienic condition lead to spoilage of food which when consumed can lead to serious illness.

Question 4.
Why oil is added while making pickle?
Answer:
Oil seals off the air from the item that is being pickled and thus inhibit the growth of most of the microorganisms.

Question 5.
Ria thought of making curd. For this, she took lukewarm milk, mixed some curd into it and stir well. She kept the mixture in fridge. Next day she observed that curd was not set. Can you tell why the curd did not set?
Answer:
Curd did not set because she kept the mixture in fridge. Lower temperature of fridge retarded the growth of Lactobacillus in the mixture.

Question 6.
Why do idli and dosa maker add some yeast or old batter of pervious day to the newly-made batter and keep it for one day?
Answer:
For fermentation of idli and dosa yeast or old batter is added. Fermentation makes idli fluffy and dosa crispy, and change the flavour.

Microorganisms: Friend and Foe Class 8 Extra Questions Value Based (VBQs)

Question 1.
Seema got cough and cold badly. Her teacher asked her to take rest at home and use handker chief while sneezing and coughing. She obeyed her teacher.
(a) Why should we keep a handkerchief on nose and mouth while sneezing or coughing?
(b) What are the modes of transfer of diseases from infected to healthy person?
(c) Do you think Seema’s teacher decision was right? Why?
(d) What value of Seema is shown here?
Answer:
(a) We should keep a handkerchief on nose and mouth while sneezing or coughing because fine droplets carrying thousands of viruses or bacteria spread in the air.
(b) Air, water, food, carriers and physical contact.
(c) Yes, because cough and cold spreads through air and there are chances that other students may also get infected.
(d) Seema is an obedient girl.

Question 2.
On Rahul’s birthday, his mother prepared many dishes for him. After having their meal, they found that many food items were leftover. Rahul’s mother kept these leftovers in a air-tight container and refrigerate them.
(a) What is food preservation?
(b) What will happen to the food if it is not refrigerated?
(c) What is the role of refrigeration in food preservation method?
Answer:
(a) The methods used for prevention of spoiling of food by the action of microbes is called food preservation.
(b) The food will get spoil and emit bad smell with changed colour or taste.
(c) Refrigeration retards or slow down the growth of microorganisms and enzyme activity on food. Thus, it prevents spoilage of food.
(d) Rahul’s mother is intelligent, economical, have scientific aptitude towards preservation of food.

In this page, we are providing Crop Production and Management Class 8 Extra Questions and Answers Science Chapter 1 pdf download. NCERT Extra Questions for Class 8 Science Chapter 1 Crop Production and Management with Answers will help to score more marks in your CBSE Board Exams.

Class 8 Science Chapter 1 Extra Questions and Answers Crop Production and Management

Extra Questions for Class 8 Science Chapter 1 Crop Production and Management with Answers Solutions

Crop Production and Management Class 8 Extra Questions Very Short Answer Type

Question 1.
What is the name of the undesirable plants that grow among the crops?
Answer:
Weeds

Question 2.
Name one weed.
Answer:
Wild oat

Question 3.
Name the methods applied for weeding.
Answer:

• Manual method
• Chemical method
• Biological method

Question 4.
Name the chemicals that are used to remove weeds.
Answer:
Weedicides

Question 5.
Name a tool which is used for removing weeds and for loosening soil.
Answer:
Hoe

Question 6.
What is the process of loosening and turning of the soil called?
Answer:
Tilling or ploughing

Question 7.
What are the substances which are added to the soil in the form of nutrients called?
Answer:
Manure and fertilisers

Question 8.
What is the process of supplying water to crops at different intervals is called?
Answer:
Irrigation

Question 9.
What are the sources of irrigation?
Answer:
Wells, tubewells, ponds, lakes, etc.

Question 10.
What is the process of separation of grain from chaff called?
Answer:
Winnowing

Question 11.
Name two crops belonging to rabi crop.
Answer:
Pea, gram

Question 12.
Name the ideal months for the harvesting of rabi crops.
Answer:
March/April

Question 13.
Name two kharif crops.
Answer:
Soybean, groundnut

Question 14.
Name the ideal months for sowing kharif crops.
Answer:
June/July

Question 15.
Name any two fertilisers.
Answer:
NPK, Diammonium phosphate

Crop Production and Management Class 8 Extra Questions Short Answer Type

Question 1.
What is a crop?
Answer:
Crop is the term used to describe a plant that is grown in a field on a large scale. For example, cereal crops, wheat crops.

Question 2.
What do you mean by produce?
Answer:
The products obtained from the crops are called produce.

Question 3.
What do you mean by the term agricultural practice?
Answer:
Agricultural practices are those practices which involve the necessary steps to be taken during production of crops.

Question 4.
Explain the term levelling.
Answer:
Levelling is the process of breaking down the larger lumps of soil, and then levelling them by using a leveller.

Question 5.
What are the advantages of levelling?
Answer:
Following are the advantages of levelling:

• Levelling helps to prevent soil erosion caused by wind or air.
• It helps in sowing the seeds uniformly, and thus helps the plants to grow uniformly too.
• It helps in proper irrigation by allowing the water to get distributed uniformly throughout the soil.

Question 6.
What is a plough?
Answer:
A plough is an equipment for ploughing. It is mainly made of a wooden shaft called a plough-shaft, attached to a triangular iron blade called ploughshare.

Question 7.
What is a cultivator?
Answer:
Cultivator is a farm implement used for stirring and pulverizing the soil for planting crops.

Question 8.
Explain the term transplantation.
Answer:
Some of the crops are first grown in the nurseries and then transferred to the main field. This process is known as transplantation.

Question 9.
What are the advantages of manure?
Answer:
Following are some advantages of manure:

• It enhances water-holding capacity of soil.
• It improves soil quality.
• It promotes the growth of soil friendly microbes.
• It is renewable, biodegradable and eco-friendly.

Question 10.
What are weedicides? Give some examples.
Answer:
Weedicides are the chemicals that are used to remove weeds. Some commonly used weedicides are 2, 4-D and metachlor.

Crop Production and Management Class 8 Extra Questions Long Answer Type

Question 1.
What do you mean by the term crop? Explain briefly the types of crops.
Answer:
Crop is the term used to describe a plant that is grown in a field on a large scale. For example, cereal crops, pulses and fruit crops. The crops grown in India can be classified as kharif and rabi.

Kharif crops are sown in the rainy season by June/July and are harvested by September/October. Thus they are also known as summer season crops. For example, rice, maize, etc.

Rabi crops are sown in the winter season in October or November and are harvested by March/April. Thus, they are also called winter season crops. For example, mustard, wheat, potato, etc.

Question 2.
What is ploughing or tilling? State its advantages.
Answer:
The process of loosening and turning of the soil is called tilling or ploughing. This is done by using a plough. Ploughs are made of wood or iron. Following are the advantages of ploughing or tilling:

• Ploughing loosens the soil and makes it aerated.
• It helps in mixing organic matter with the soil uniformly.
• It initiates the growth of natural agents and microorganisms and thus, keeps the soil fertile.
• It increases the water holding capacity of soil.
• It helps in easy penetration of root into the soil.

Question 3.
Define the term agricultural practices and also state the important steps taken during crop production.
Answer:
Agricultural practices are those practices which involves the necessary steps to be taken during production of crops. There are number of steps of crop production which are to be done very carefully to ensure that crops get produced timely. Some of the most important steps taken during crop production are as under:

• Soil preparation
• Sowing
• Adding manure and fertilisers
• Irrigation
• Weeding
• Harvesting
• Threshing and winnowing
• Storage of grains

Question 4.
What is irrigation? Name the two main methods of irrigation and define them briefly.
Answer:
The artificial method of watering the plants for assisting in the growth of the plants is called irrigation. The two main methods of irrigation are:
(i) Traditional method: The traditional method of irrigation is very less expensive and they often lead to wastage of water. Traditional method of irrigation involves chain pump, dhekli, moat (the pulley system) and rahat (lever system).

(ii) Modern method: Modern methods of irrigation are more inclined towards the use of diesel, bio¬gas, solar energy and electricity for lifting water.
The two most important modern system of irrigation are:

• Sprinkler irrigation system
• Drip irrigation system

Question 5.
What do you mean by weeding? Why the process of weeding necessary? Name the methods applied for weeding.
Answer:
The undesirable plants that grow among the crops are called weeds. The process of removing these weeds is known as weeding. Weeds compete with the crop plants for nutrients and space. They grow much rapidly than the crop plant. So weeding is necessary.

Methods applied for weeding are as follows:
(i) Manual method: Manual method of removing weeds is the most time consuming method. In this system weeds are controlled by hand pulling, digging, shallow tillage, etc., by using certain implements like khurpi, hoe, etc.

(ii) Chemical method: In this method chemicals called, weedicides are used to remove weeds. For example, metachlor and 2, 4-D.

(iii) Biological control method: This method is the most commonly used method of weed control. It involves the use of some specific insects that destroy the growth of some specific weeds. For example, leafy spurge, a weed, is controlled by using flea beetles.

Question 6.
Write short note on the terms:
(i) Storage
(ii) Harvesting
Answer:
(i) Storage: Storage of produce is an important task. If the crop grains are to be kept for longer time, they should be safe from moisture, insects, rats and microorganisms. Before storing, the grains are properly dried in the sun to reduce the moisture in them. This prevents the attack by insect pests, bacteria and fungi. Grains are stored by farmers in jute bags or metallic bins. However, large scale storage of grains is done in silos and granaries to protect them from pests like rats and insects.

(ii) Harvesting: After maturation of crop, harvesting is an important task. In harvesting, crops are pulled out or cut close to the ground. It usually takes 3 to 4 months for a cereal crop to mature. Harvesting in our country is either done manually by sickle or by machine called harvester.

Crop Production and Management Class 8 Extra Questions HOTS

Question 1.
Why the depth at which seeds are planted is important?
Answer:
If the seed is planted too deep then it will not get enough sunlight to germinate. If the seed is planted too shallow then it will not get enough soil to support germination. The depth for sowing seed also depends upon the seed size.

Question 2.
Why sowing seeds with seed drill is better than broadcasting?
Answer:
Seed drill sows the seeds uniformly at proper distances and depths, whereas broadcasting of seeds scatter them non-uniformly on the ground surface which are susceptible to be picked up by birds.

Question 3.
How can nitrogen be replenished in soil naturally?
Answer:
Through crop rotation with a leguminous crop the nitrogen can be replenished in soil naturally. The leguminous plants, like peas, beans, soybeans, peanuts, etc., have nitrogen-fixing bacteria in their root nodules. The nitrogen-fixing bacteria, viz., Rhizobium, fixes atmospheric nitrogen (N₂) into ammonium (NH₄₊) which is used by the plants.

Question 4.
Why is it advisable to wash fruits and vegetables before using them?
Answer:
Fruits and vegetables may contain many pesticides, used during the crop production practices, on them along with other germs and dust.

Question 5.
What is biological control of pest? How is it beneficial?
Answer:
Method of controlling pests including insects, mites, weeds, etc., with the help of other living organisms are known as biological control of pest. The controlling agents are very much particular of their host pest. For example, lady bugs controls aphids, mites, scale insects, etc., which harm the crops. A wasp eats up bollworms or other caterpillars on cotton plant.
Benefits of biocontrol agents are:

• Less costly
• Give protection to the crop throughout the crop period
• Eco-friendly
• Harmless to human beings and beneficial to flora and fauna

Crop Production and Management Class 8 Extra Questions Value Based (VBQs)

Question 1.
Rajan felt worried about the condition of water scarcity in his village during the cropping season. He went to Ministry of Agriculture and Farmers Welfare of his area to get the solution of this problem. There he came to know about effective method of irrigation and drought resistant varieties of crop. He requested the head of department of the ministry to arrange some workshop on this topic to educate the farmers in these methods.
(a) Name modern methods of irrigation that help us to use water economically.
(b) What is drought resistant varieties of crop?
(c) Can you name some crops that require less amount of water?
(d) What value of Raj is shown here?
Answer:
(a) Drip irrigation system and sprinkler method.
(b) Crops that need very little amount of rainfall or irrigation to grow are called drought resistant varieties of crop.
(c) Sorghum, pearl millet, chickpea, groundnut, etc.
(d) Rajan is concerned, aware, sensitive and intelligent.

Question 2.
Krishi Vigyan Kendra (KVK), a constituent extension centre of Tamil Nadu Veterinary and Animal Sciences University, organised a farmer’s workshop on organic farming in vegetable cultivation at Kalayarkoil to commemorate the World Soil Day.
(a) What is organic farming?
(b) What is the advantage of organic farming?
(c) What are the health benefits of organic farming?
(d) What values of KVK are shown here?
Answer:
(a) Organic farming is a form of agriculture that relies on techniques such as crop rotation, green ma-nure, compost and biological pest control.

(b) Advantages of organic farming are:

• Do not use any harmful chemicals
• Crops have better taste and nutrition
• Eco-friendly
• Cost effective

(c) Organic farming uses all the natural ways to provide nutrients and to get rid of the pests. So it reduces the harmful effects of pesticides and fertilisers on human beings.

(d) Krishi Vigyan Kendra shows concern about the growing use of pesticides, fertilisers, etc., and their adverse effect on human health. It is spreading awareness amongst farmers about eco-friendly ways of cultivating crops.