Lakhmir Singh Science Class 8 Solutions Chapter 5 Coal and Petroleum

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S Chand Science Class 8 Solutions Chapter 5 Coal and Petroleum

Lakhmir Singh Science Class 8 Chapter 5 Very Short Answer Type Questions

Question 1.
Name three useful products of coal.
Answer:
The three useful products of coal are following:
Coke: It is a tough, porous and black substance. It is almost pure form of carbon.
Coal tar: It is a mixture of about 200 substances. It is a black, thick liquid with unpleasant smell.
Coal gas: It is obtained during the processing of coal to get coke.

Question 2.
Which product of coal is used as a reducing agent in the extraction of metals?
Answer:
Coke is used as a reducing agent in the extraction of metals. It is used in the manufacture of steel and in the extraction of many metals.

Question 3.
Name the process by which plant material (or vegetation) buried deep under the earth was slowly converted into coal.
Answer:
Carbonisation is the process by which plant material or vegetation buried deep under the earth was slowly converted into coal. Since, coal was formed from the remains of vegetation, it is also known as fossil fuel.

Question 4.
Name the product of coal which is thick black liquid having an unpleasant smell.
Answer:
Coal tar is the product of coal which is a thick black liquid having an unpleasant smell. It is a mixture of about 200 substances.

Question 5.
Name any five substances used in everyday life which are manufactured starting from the products of coal tar.
Answer:
Substances used in everyday life which are manufactured starting from the products of coal tar are following:
Synthetic dyes, drugs, perfumes, plastics and paints. Naphthalene balls used to repel moths and other insects are also obtained from coal tar.

Question 6.
Name an important source from which naphthalene balls are obtained.
Answer:
Naphthalene balls used to repel moths and other insects are obtained from coal tar.

Question 7.
Which substance is used for metalling the roads these days in place of coal tar?
Answer:
Bitumen, a petroleum product, is used in place of coal-tar for metalling the roads.

Question 8.
Name the most common fuel used in light motor vehicles.
Answer:
Petrol is used as a fuel in light motor vehicles such as motor cycles, scooters and cars.

Question 9.
Name the fuel which is used in jet aircraft engines.
Answer:
Kerosene is used as fuel in jet aircraft engines.

Question 10.
Name the petroleum product used to drive heavy vehicles.
Answer:
Diesel is used as a fuel for heavy motor vehicles and electric generators.

Question 11.
Name the petroleum product which is commonly used for electric generators.
Answer:
Diesel is used as a fuel for electric generators.

Question 12.
What is the full form of LPG?
Answer:
The full form of LPG is Liquefied petroleum gas. It is also referred as propane or butane. It is flammable and is used as fuel in heating appliances, cooking equipment and vehicles.

Question 13.
Is it possible to extract petroleum from under the sea bed?
Answer:
Petroleum can be extracted from under the sea bed. It can be extracted with giant drilling machines. The layer containing petroleum oil and gas is above that of water.

Question 14.
What is the full form of CNG?
Answer:
The full form of CNG is compressed natural gas. Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG).

Question 15.
Name the major component of natural gas.
Answer:
Natural gas consists of primarily of methane but also contains ethane, propane and heavier hydrocarbons. It also contains small amounts of nitrogen, carbon dioxide, hydrogen sulphide and very little amount of water.

Question 16.
Name any two places in India where natural gas is found.
Answer:
India has huge reserves of natural gas. It has been found in Tripura, Rajasthan, Maharashtra and in the Krishna Godavari delta.

Question 17.
Name a fossil fuel other than coal and petroleum.
Answer:
Natural gas is a fossil fuel other than coal and petroleum. Natural gas consists of ethane, propane and heavier hydrocarbons.

Question 18.
Name two places in India where coal is found.
Answer:
India has abundant domestic reserves of coal. Coal can be found in Jharkhand and West Bengal.

Question 19.
Name the petroleum product used for surfacing of roads.
Answer:
Bitumen is used for the surfacing of roads.

Question 20.
Name any four places in India where petroleum is found.
Answer:
In India, oil is found in Assam, Gujarat, Mumbai High and in the river basins of Godavari and Krishna.

Question 21.
Write the full form of PCRA.
Answer:
The full form of PCRA is Petroleum Conservation Research Association. It advises people how to save petrol/diesel while driving.

Question 22.
State whether the following statements are true or false:
(a) Coke is almost pure from carbon.
(b) Coal tar is a mixture of various substances.
(c) Kerosene is not a fossil fuel.
(d) CNG is more polluting than petrol.
(e) Fossil fuels can be made in the laboratory.
Answer:
(a) This statement is True.
It is a tough, porous and black substance. It is almost pure form of carbon.
(b) This statement is True.
Coal tar is the product of coal which is a thick black liquid having an unpleasant smell. It is a mixture of about 200 substances.
(c) This statement is False.
Kerosene is a fossil fuel. It is used as a fuel for stoves, lamps and for jet aircrafts.
(d) This statement is False.
CNG is less polluting than petrol. It is a clean burning fuel. It produces 45% less hydrocarbons than petrol.
(e) This statement is False.
The formation of fossil fuels is a very slow process. These are formed under very high pressure and high temperature. The conditions for their formation cannot be created in the laboratory.

Question 23.
Fill in the following blanks with suitable words:
(a) Fossil fuels are…………and…….
(b) Coal contains mainly……………
(c) The slow process of conversion of dead vegetation into coal is called……………
(d) The process of separation of different constituents from petroleum is called………………
(e) The least polluting fuel for vehicles is…….
(f) The burning of fossil fuels causes air………….and also leads to global……………
Answer:
(a) The correct Answer: is ………Coal, petroleum and ………natural gas.
Coal, Petroleum and natural gas are formed from the dead remains of living organisms or fossils. So, these are all known as fossil fuels.
(b) The correct Answer: is ………… carbon.
Coal is formed from the remains of vegetation, it is also called a fossil fuel. Being produced from vegetation it mainly contains carbon.
(c) The correct Answer: is …. Carbonisation.
Carbonisation is the process by which plant material or vegetation buried deep under the earth was slowly converted into coal. Since, coal was formed from the remains of vegetation, it is also known as fossil fuel.
(d) The correct Answer: is ……refining.
Petroleum is a mixture of various constituents such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc. The process of separating the various constituents or fractions of petroleum is known as refining. It is carried out in a petroleum refinery.
(e) The correct Answer: is ……CNG.
The full form of CNG is compressed natural gas. Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG).
(f) The correct Answer: is ……. pollution; warming.
Burning of fossil fuels affects the environment because they release carbon dioxide and other harmful gases such as Sulphur dioxide, nitrogen oxides and carbon monoxides. These gases trap heat in the earth’s atmosphere and causes global warming which contributes to global climate change.

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Question 24.
Explain why, fossil fuels are exhaustible natural resources.
Answer:
The amount of fossil fuels is very limited in nature. They can be exhausted by human activities. The formation of fossil fuels is a very slow process. These are formed under very high pressure and high temperature. For example, coal, petroleum and natural gas are fossil fuels. Coal was formed by the process of carbonisation. Carbonisation is the process by which plant material or vegetation buried deep under the earth was slowly converted into coal.

Question 25.
Describe how coal was formed. What is this process called?
Answer:
Coal was formed millions and millions of years ago in swampy forests where some plants died and some grew simultaneously. As the years passed, the layers of dead plants collected one over the other and formed thick layers. With changing weather conditions, more plants grew and the layers of dead plants continued to form deep. Coal is a fossil fuel. The heat and the pressure produced physical and chemical changes in the layers which resulted in the rich carbon content and forced the oxygen into the environment. This rich carbon content became as coal. This process of forcing the oxygen out and leaving behind carbon content was called as carbonisation. In other words, Carbonisation is the process by which plant material or vegetation buried deep under the earth was slowly converted into coal. This is a very slow process and usually, takes millions of years.

Question 26.
What is happens when coal is heated in air? State the uses of coal.
Answer:
When heated in air, coal burns and produces mainly carbon dioxide gas. Coal can be processed in industry to get some useful products such as coke, coal tar and coal gas. Coal is used as a fuel in industries and was used to cook food. It was used in railway engines to produce steam to run the engine. It is used in thermal power plants to produce electricity.

Question 27.
State the uses of coke.
Answer:
Coke is a very useful product of coal. It is a tough, porous and black substance. It is almost pure form of carbon. It is used as a reducing agent in the extraction of metals. It is also used in the manufacture of steel and in the extraction of many metals.

Question 28.
What are the constituents of coal gas? State one use of coal gas.
Answer:
Coal gas is a product of coal. It is obtained during the processing of coal to get coke. Coal gas contains a variety of gases like hydrogen, carbon monoxide, methane and some volatile hydrocarbons. It also contains small quantities of gases such as carbon dioxide and nitrogen. It is used as a fuel in many industries situated near the coal processing plants.

Question 29.
What are the major products (or fractions) of petroleum refining? Give one use of each petroleum product.
Answer:
The process of separating the various constituents or fractions of petroleum is known as refining. It is carried out in a petroleum refinery. The main products of petroleum refining are petroleum gas, petrol, diesel, lubricating oil, paraffin wax and kerosene. Following are the uses of petroleum products:
Petroleum gas is used as fuel for home and industry.
Petrol is used as a Motor fuel, aviation fuel and solvent for dry cleaning.
Diesel is used as a fuel for heavy motor vehicles and electric generators.
Lubricating oil is used as a lubricant.
Kerosene is used as a fuel for stoves, lamps and for jet aircrafts.
Paraffin wax is used in ointments, candles and Vaseline etc.
Bitumen Paints are used in road surfacing.

Question 30.
What are the advantages of using natural gas (or CNG) as a fuel?
Answer:
CNG is compressed natural gas. Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG). It is advantageous to use CNG as a fuel because it is less polluting than petrol. It is a clean burning fuel. It produces 45% less hydrocarbons than petrol. The great advantage of CNG is that it can be used directly for burning in homes and factories where it can be supplied through pipes.

Question 31.
State the various uses of natural gas.
Answer:
Natural gas is a very important fossil fuel because it is easy to transport through pipes. It can be used as a fuel in homes and factories. It is also used as a starting material for the manufacture of a number of chemicals and fertilizers.

Question 32.
What is CNG? State its one use.
Answer:
CNG is compressed natural gas. Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG). It can be used as a fuel in homes and factories. It is also used as a starting material for the manufacture of a number of chemicals and fertilizers.

Question 33.
Where the natural gas found? Why is natural gas called a clean fuel?
Answer:
India has huge reserves of natural gas. It has been found in Tripura, Rajasthan, Maharashtra and in the Krishna Godavari delta. It is advantageous to use CNG as a fuel because it is less polluting than petrol. It is a clean burning fuel. It produces 45% less hydrocarbons than petrol. The great advantage of CNG is that it can be used as fuel in homes and factories where it can be supplied through pipes.

Question 34.
What are the advantages of using LPG as fuel?
Answer:
LPG stands for liquified Petroleum Gas. It is used as fuel for home and industry. Advantages of using LPG as a fuel is that it is non-toxic and reduces the interior pollution by 90% as compared to other fuels such as coal or wood. The carbon dioxide emissions are very low. It is an economical fuel source. It burns very efficiently, with very low combustion emissions and does not create black smoke.

Question 35.
Name any five useful substances which are manufactured from petrochemicals.
Answer:
Many useful substances are obtained from petroleum and natural gas. These are termed as ‘Petrochemicals’. These are used in the manufacture of detergents, fibres (polyester, nylon, acrylic etc.), polythene and other man-made plastics. Hydrogen gas obtained from natural gas, is used in the production of fertilisers (urea).

Question 36.
Which material is called ‘black gold’? why?
Answer:
Many useful substances are obtained from petroleum and natural gas. These are termed as ‘Petrochemicals’. These are used in the manufacture of detergents, fibres such as polyester, nylon, acrylic etc., polythene and other man-made plastics. Hydrogen gas obtained from natural gas, is used in the production of fertilisers such as urea. Due to its great commercial importance, petroleum is also called ‘black gold’.

Question 37 A.
Where and when was the world’s first oil well drilled?
Answer:
The world’s first oil well was drilled in Pennsylvania, USA, in 1859

Question 37 B.
Where and when was oil first struck in India?
Answer:
At Makum in Assam, in 1867, oil was stuck in India. Oil is found in Assam, Gujarat, Mumbai High and in the river basins of Godavari and Krishna.

Question 38.
State one use each of the following products of petroleum:
(a) petroleum gas,
(b) petrol,
(c) Diesel,
(d) Lubricating oil,
(e) Bitumen
Answer:
(a) Petroleum gas is used as fuel for home and industry.
(b) Petrol is used as a Motor fuel, aviation fuel and solvent for dry cleaning.
(c) Diesel is used as a fuel for heavy motor vehicles and electric generators.
(d) Lubricating oil is used as a lubricant.
(e) Bitumen Paints are used in road surfacing.

Question 39.
What is the major cause of air pollution? Write the various tips for minimizing the wastage of petrol/diesel while driving vehicles.
Answer:
Burning of fossil fuels is the major cause of air pollution. Burning of fossil fuels affects the environment because they release carbon dioxide and other harmful gases such as Sulphur dioxide, nitrogen oxides and carbon monoxides. These gases trap heat in the earth’s atmosphere and causes global warming which contributes to global climate change. It is therefore necessary that we use these fuels only when absolutely necessary. This will result in better environment, smaller risk of global warming and their availability for a longer period of time. In India, the Petroleum Conservation Research Association (PCRA) advises people how to save petrol or diesel while driving. Their tips are:

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

Question 40.
Why should we use fossil fuels only when absolutely necessary?
Answer:
Burning of fossil fuels affects the environment due to the release carbon dioxide and other harmful gases such as Sulphur dioxide, nitrogen oxides and carbon monoxides. These gases trap heat in the earth’s atmosphere and causes global warming which contributes to global climate change. It is therefore necessary that we use these fuels only when absolutely necessary. It took millions of years for the dead organisms to get converted into these fuels. On the other hand, the known reserves of these fuels will last only a few hundred years. It is therefore, necessary to conserve these natural resources. This will also result in better environment, smaller risk of global warming and their availability for a longer period of time.

Question 41.
State (a) two uses of kerosene, and (b) two uses of paraffin wax.
Answer:
Kerosene is used as a fuel for stoves, lamps and for jet air crafts.
Paraffin wax is used in ointments, candles and Vaseline etc.

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Lakhmir Singh Science Class 8 Chapter 5 Long Answer Type Questions

Question 42 A.
What is meant by inexhaustible natural resources? Name two inexhaustible natural resources.
Answer:
The resources which are present in unlimited quantity in nature and are not likely to be exhausted by human activities are known as inexhaustible natural resources. For example, sunlight and air are inexhaustible natural resources.

Question 42 B.
What is meant by exhaustible natural resources? Name any two exhaustible natural resources.
Answer:
The resources which are present in a limited amount in nature are known as exhaustible natural resources. They can be exhausted by human activities. Examples of these resources are forests, wildlife, minerals, coal, petroleum, natural gas etc.
Examples: Forests, wildlife, minerals, coal, petroleum, natural gas etc.

It is, therefore, necessary that we use these fuels only when absolutely necessary. It took millions of years for the dead organisms to get converted into coal, petroleum, natural gas etc.

Question 43 A.
What are fossil fuels? Name three fossil fuels.
Answer:
The exhaustible natural resources which are formed from the dead remains of living organisms or fossils are known as fossil fuels. For example, coal, petroleum and natural gas are fossil fuels. The resources are present in limited amount in nature and are known as exhaustible natural resources. They can be exhausted by human activities.

Question 43 B.
Describe how, fossil fuels were formed.
Answer:
The fossil fuel such as coal is formed from the remains of dead vegetation. Earth had dense forests in low lying wetland areas about 300 million years ago. Due to natural processes, like flooding, these forests got buried under the soil. Due to soil deposition over these dead plants, they were compressed. The temperature also increased as they sank deeper and deeper. Under high pressure and high temperature, dead plants got slowly converted to coal. As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonisation. Since it was formed from the remains of vegetation, coal is also called a fossil fuel.

The fossil fuel such as petroleum is formed from the dead animals under the sea. As these organisms died, their bodies settled at the bottom of the sea. They got covered with layers of sand and clay. Over millions of years, in the absence of air, with high temperature and high pressure, these the dead organisms were transformed into petroleum and natural gas.

Question 44 A.
What is petroleum? Where does petroleum occur?
Answer:
The exhaustible natural resources which are formed from the dead remains of living organisms or fossils are known as fossil fuels. For example, coal, petroleum and natural gas are fossil fuels. The fossil fuel such as petroleum is formed from the dead animals under the sea. As these organisms died, their bodies settled at the bottom of the sea.

They got covered with layers of sand and clay. Over millions of years, in the absence of air, with high temperature and high pressure, these the dead organisms were transformed into petroleum and natural gas. The main constituents of petroleum are petroleum gas, petrol, diesel, lubricating oil, paraffin wax and kerosene. Petroleum can be extracted from under the sea bed. It can be extracted with giant drilling machines. The layer containing petroleum oil and gas is above that of water.

Question 44 B.
Describe the process of formation of petroleum.
Answer:
The fossil fuel such as petroleum is formed from the dead animals under the sea. As these organisms died, their bodies settled at the bottom of the sea. They got covered with layers of sand and clay. Over millions of years, in the absence of air, with high temperature and high pressure, these the dead organisms were transformed into petroleum and natural gas.

Question 45 A.
What are petrochemicals? Name any two petrochemicals.
Answer:
The fossil fuel such as petroleum is formed from the dead animals under the sea. As these organisms died, their bodies settled at the bottom of the sea. They got covered with layers of sand and clay. Over millions of years, in the absence of air, with high temperature and high pressure, these the dead organisms were transformed into petroleum and natural gas. Many useful substances are obtained from petroleum and natural gas. These are termed as ‘Petrochemicals’. These are used in the manufacture of detergents, fibres such as polyester, nylon, acrylic etc., polythene and other man-made plastics.

Question 45 B.
Why are petro-chemicals so important?
Answer:
Many useful substances are obtained from petroleum and natural gas. These are termed as ‘Petrochemicals’. These are used in the manufacture of detergents, fibers such as polyester, nylon, acrylic etc., polythene and other man-made plastics. Hydrogen gas obtained from natural gas is used in the production of fertilizers such as urea. Due to its great commercial importance, petroleum is also called ‘black gold’.

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Question 46.
Which one of the following is not a fossil fuel?
A. petrol
B. coke
C. charcoal
D. coal
Answer:
C. charcoal
Charcoal is mostly pure carbon which is made by cooking wood in a low oxygen environment. This process can take days and burns off volatile compounds such as water, methane, hydrogen, and tar.

Petrol, coke and coal are fossil fuels which are formed from the dead remains of living organisms or fossils.

Question 47.
The major component of LPG is:
A. hydrogen
B. carbon monoxide
C. methane
D. butane
Answer:
D. butane
The full form of LPG is Liquefied petroleum gas. It is also referred as propane or butane. It is flammable and is used as fuel in heating appliances, cooking equipment and vehicles.

Question 48.
Which is the major component of CNG?
A. ethane
B. propane
C. methane
D. butane
Answer:
A. ethane
CNG consists primarily of methane but also contains ethane, propane and heavier hydrocarbons. It also contains small amounts of nitrogen, carbon dioxide, hydrogen sulphide and very little amount of water.

Question 49.
The gas which occurs above the petroleum oil trapped under the rocks is called:
A. Biogas
B. Petroleum gas
C. Natural gas
D. Coal gas
Answer:
B. Petroleum gas
Petroleum can be extracted from under the sea bed. It can be extracted with giant drilling machines. The layer containing petroleum oil and gas is above that of water.

Question 50.
Which of the following is being used as a source of hydrogen gas needed to manufacture fertilizers?
A. biogas
B. natural gas
C. coal gas
D. petroleum gas
Answer:
B. natural gas
The full form of CNG is compressed natural gas. Natural gas is a very important fossil fuel because it is easy to transport through pipes. It can be used as a fuel in homes and factories. It is also used as a starting material for the manufacture of a number of chemicals and fertilizers.

Question 51.
One of the following is not an exhaustible source of energy. This one is:
A. natural gas
B. petroleum gas
C. coal gas
D. biogas
Answer:
D. biogas
Biogas can be produced from raw materials such as agricultural waste, manure, plant material, green waste or food waste. It is a renewable source of energy. Natural gas, coal gas and petroleum gas are fossil fuels and are nonrenewable sources of energy.

Question 52.
The slow process by which the large land plants and trees buried deep under the earth have become coal is called:
A. carbonation
B. carburetion
C. carbonisation
D. carbocation
Answer:
C. carbonisation
Carbonisation is the process by which plant material or vegetation buried deep under the earth was slowly converted into coal. Since, coal was formed from the remains of vegetation, it is also known as fossil fuel.

Question 53.
Which of the following is used as a reducing agent in the extraction of iron metal?
A. coal
B. bitumen
C. charcoal
D. coke
Answer:
Coke is a tough, porous and black substance. It is almost pure form of carbon. It is used as a reducing agent in the extraction of metals. It is used in the manufacture of steel and in the extraction of many metals.

Question 54.
Which of the following is usually referred to as ‘black gold’?
A. coke
B. coal tar
C. petroleum
D. coal
Answer:
Many useful substances are obtained from petroleum and natural gas. These are termed as ‘Petrochemicals’. Due to its great commercial importance, petroleum is also called ‘black gold’.

Question 55.
the various compounds present in coal tar are separated by the process of:
A. simple distillation
B. destructive distillation
C. fractional distillation
D. fractional crystallization
Answer:
Coal tar is a mixture of about 200 substances. It is a black, thick liquid with unpleasant smell. Synthetic dyes, drugs, perfumes, plastics and paints. Naphthalene balls used to repel moths and other insects are also obtained from coal tar.

Question 56.
Which of the following is not obtained as a fractional during the refining of petroleum?
A. kerosene
B. natural gas
C. lubricating oil
D. bitumen
Answer:
B. natural gas
Natural gas is a fossil fuel other than coal and petroleum. Petroleum can be extracted with giant drilling machines. The layer containing petroleum oil and natural gas is above that of water.

Question 57.
Which one of the following is an inexhaustible natural resource?
A. coal
B. petroleum
C. water
D. forests
Answer:
C. water
Water is an inexhaustible natural resource because it is available abundantly in nature.

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Question 58.
The substances W is a fossil fuel. It occurs deep below the ground in certain areas of the earth. Another fossil fuel X is found trapped above the deposits of W. when W is subjected to a process called Y, then a number of different products are collected at different temperature ranges which are put to different uses. A special grade of product z obtained in this way is used an aviation fuel in jet aero planes.
(a) What are (i) W, and (ii) X
(b) what is the physical state of (i) W, and (ii) X?
(c) Name the process Y?
(d) Name the product Z?
Answer:
(a) The substance W is Petroleum and substance Y is Natural gas. Natural gas is a fossil fuel other than coal and petroleum. Petroleum can be extracted with giant drilling machines. The layer containing petroleum oil and natural gas is above that of water.

(b) The physical state of W is a liquid. Petroleum is a dark oily liquid. It has an unpleasant odor. It is a mixture of various constituents such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc.
The physical state of X is Gas. Natural gas is a fossil fuel other than coal and petroleum. Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG). It can be used as a fuel in homes and factories. It is also used as a starting material for the manufacture of a number of chemicals and fertilizers.

(c) Process Y is known as Fractional distillation. It is the process of separation of a mixture into its components, by the difference in their boiling points. Mixture is heated which causes one or more components to vaporize at different temperatures. The process of separating the various constituents or fractions of petroleum is known as refining. It is carried out in a petroleum refinery.

(d) The product Z is Kerosene. Kerosene is one of the constituent of petroleum. It is a fossil fuel. It is used as a fuel for stoves, lamps and for jet air crafts.

Question 59.
The material A is fossil fuel which is extracted from the earth. It is said to be formed from the buried, large land plants by a very slow process B. when A is heated in the absence of air in a process called C, then it gives three products D, E and F. The product D is used as a reducing agent in the extraction of metals, the product E is used as an industrial fuel whereas the product F has been traditionally used for metallic the roads.
(a) What could material A be?
(b) What is (i) physical state, and (ii) colour, of A?
(c) Name the processes (i) B, and (ii) C.
(d) What are (i) D, (ii) E, and (iii) F?
Answer:
(a) The material A is Coal. Coal is a fossil fuel. It was formed by the process of carbonisation. Carbonisation is the process by which plant material or vegetation buried deep under the earth was slowly converted into coal. This is a very slow process and usually takes millions of years.

(b) Coal exists as solid. It is as hard as stone and is black in colour.

(c) The process B is carbonization. It is a process by which plant material or vegetation buried deep under the earth was slowly converted into coal. This is a very slow process and usually takes millions of years.
The process C is Destructive distillation. Destructive distillation is a chemical process of decomposition of a solid by heating it in a closed container. The volatile constituents produced in this process can be separated. Coal is processed in industry to get some useful products such as coke, coal tar and coal gas.

(d) The product D is coke, E is Coal gas and F is Coal tar.
Coal is processed in industry by the process of destructive distillation to get some useful products such as coke, coal tar and coal gas. Coke is a tough, porous and black substance. It is almost pure form of carbon. Coal is a mixture of about 200 substances. It is a black, thick liquid with unpleasant smell. Coal gas is obtained during the processing of coal to get coke.

Question 60.
The fossil fuel P is formed under the earth by the decomposition of vegetable matter lying under water by the action of anaerobic bacteria. The major component of fuel P is Question The fossil fuel P is used as a source of gas R needed to manufacture nitrogenous fertilizers. When P is filled in metal cylinders and used as a fuel in motor vehicles, it is called S. What are P, Q, R and S?
Answer:
The fossil fuel P is known as Natural Gas. Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG). It can be used as a fuel in homes and factories. It is also used as a starting material for the manufacture of a number of chemicals and fertilizers.

The substance Q is Methane. It is the primary component of Natural gas. Natural gas also contains ethane, propane and heavier hydrocarbons.

The substance R is Hydrogen. Natural gas is used in the manufacture of fertilizers and is used as a source of hydrogen.

The substance S is Compressed natural gas also known as CNG. Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG). It is advantageous to use CNG as a fuel because it is less polluting than petrol. It is a clean burning fuel. It produces 45% less hydrocarbons than petrol.

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Lakhmir Singh Science Class 8 Solutions Chapter 4 Materials: Metals and Non-Metals

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Question 1.
What is the general name of the elements whose properties are intermediate between those of metals and nonmetals?
Answer:
The elements whose properties are intermediate between the properties of metals and nonmetals are called Metalloids. For example, Boron, Silicon and Germanium are metalloids. Heat and electricity can pass through metalloids but not as easily as in metals. Metalloids are also called semiconductors.

Question 2.
Name one metals and one nonmetal which exist in liquid state at room temperature.
Answer:
The metal which is liquid at room temperature is Mercury (Hg). Another metal called Gallium also exists as liquid at room temperature. Its melting point is very low and it changed into a liquid when touched.

The nonmetal which is liquid at room temperature is Bromine.

Question 3.
Name the property;
(a) Which allows metals to be hammered into thin sheets.
(b) Which enables metals to be drawn into wires.
Answer:
(a) The property of metals which allows metals to be hammered into thin sheets is called Malleability. Due this unique property, metals can be flattened into thin sheets by hammering and rolling.
(b) The property of metals which enables them to be drawn into wires is called Ductility. Due to this property metals can be stretched without breaking and drawn into thin wires. For example, Aluminum and copper are examples of highly ductile metals.

Question 4.
Name two metals which are soft and can be easily cut with a knife.
Answer:
The two metals which are soft and easily cut with a knife are Sodium and potassium. The freshly cut surface of these metals is shiny but it tarnishes quickly on contact with air. This is because these metals react with oxygen and water and becomes dull grey in colour.

Question 5.
If a metal coin is dropped on hard floor, it produces a ringing sound. What is this property of metals known as?
Answer:
The property of metals to produce sound is called Sonority. Metals produce ringing sound and are sonorous in nature.

Question 6.
Name the property of iron metal due to which it can be hammered to make objects of different shapes such as an axe, a spade or a shovel.
Answer:
The property by which iron metal can be hammered to make objects of different shapes such as axe, spade etc. is called Malleability. As a result of high malleability, iron can be flattened or beaten into thin sheets and desired objects can be made by using it.

Question 7.
Name a non-metal which is very hard.
Answer:
Diamond is the hardest non-metal. It is made of carbon atoms.

Question 8.
Name a non-metal which is good conductor of electricity?
Answer:
Carbon, in the form of Graphite is a good conductor of electricity. It conducts heat and electricity like a metal or a metalloid.

Question 9.
State on chemical property which can be used to distinguish a metal from a non-metal.
Answer:
The chemical property which can be used to distinguish between a metal and a nonmetal is the formation of positive ions by metals. Metals form positive ions whereas nonmetals form negative ions. As a result, oxides of metals are basic whereas the oxides of nonmetals are acidic in nature.

Question 10.
How do metal oxides differ from non-metal oxides?
Answer:
Metals react with oxygen to form metallic oxides. These metallic oxides are basic because they react with water to form bases. On the other hand, nonmetals react with oxygen to form nonmetallic oxides. These oxides differ from metallic oxides because they are acidic in nature. Nonmetallic oxides react with water to form acids.

Question 11.
An element forms an oxide which is acidic in nature. State whether the element is a metal or a non-metal?
Answer:
An element which forms oxide which is acidic in nature is a non-metal. This is because nonmetallic oxides react with water to form acids.

Question 12.
An element forms an oxide which is basic in nature. State whether the element is a metal or a non- metal?
Answer:
An element which forms oxide which is basic in nature is a metal. This is because metallic oxides are basic in nature and they react with water to form bases.

Question 13.
Write a word equation for the reaction of magnesium with oxygen.
Answer:
Metals react with oxygen in the air to produce metal oxides. For example, magnesium reacts with oxygen to produce magnesium oxide when it is heated in air:
Magnesium + oxygen → Magnesium oxide
It can also be written as:
Mg + O2 → 2MgO

Question 14.
Iron metal reacts slowly with the oxygen and moisture of damp air to form rust. State whether the rust formed is acidic, basic or neutral.
Answer:
Iron is metal. It reacts with oxygen to form rust. Rust is chemically known as iron oxide. Since, rust is a metal oxide, it will be basic in nature.

Question 15.
Name the gas evolved when a metal reacts with water.
Answer:
Metals react with water to produce hydrogen gas. For example, sodium reacts with water to form sodium hydroxide and hydrogen gas.

Question 16.
Name the gas evolved when a metal reacts with a dilute acid.
Answer:
Metals react with dilute acids to form metallic salts and hydrogen gas. For example, zinc reacts with dilute hydrochloric acid to form zinc chloride and hydrogen gas.

Question 17 A.
Name one metal which reacts with dilute hydrochloric acid to produce hydrogen gas.
Answer:
Sodium reacts vigorously with dilute hydrochloric acid because it is above hydrogen in the reactivity series of metals.

Question 17 B.
Name one metal which does not react with dilute hydrochloric acid.
Answer:
Copper does not react with dilute hydrochloric acid because it is below hydrogen in the reactivity series of metals.

Question 18.
Which metal is more reactive: iron or zinc?
Answer:
Zinc is more reactive than iron. Zinc is placed above iron in the reactivity series. For example, Zinc can displace iron from ferrous sulphate solution to form zinc sulphate and iron.

Question 19.
Which metal is less reactive: copper or iron?
Answer:
Copper is less reactive than iron. For example, if we put Iron nail into copper sulphate solution. Iron nail will displace copper from copper sulphate solution.

Question 20.
Name any five objects used in our everyday life which are made of metals.
Answer:
Following are the objects in our daily life which are made of metals:
Utensils – The utensils we use daily are made from copper, aluminum and iron.
Jewellery – The jewellery is made from gold and silver.
Electric wires – These are made from copper and aluminium.
Mercury- It is used in thermometers.
Table salt- Sodium is used in making table salt.

Question 21.
Name two metals which are used for making cooking utensils and water boilers for factories.
Answer:
Copper, aluminium and iron are used for making cooking utensils. Iron is used for making water boilers in factories.

Question 22.
Name two metals which are used for making electric wires.
Answer:
Copper and aluminium are used for making electric wires due to their high ductility.

Question 23.
Name the metal which is used in making thermometers.
Answer:
Mercury is used for making thermometers. It is liquid at room temperature and is a very good conductor of heat. Even a slightest change in temperature can be noted by using mercury.

Question 24.
Which metal is used to galvanize iron to protect it from rusting?
Answer:
Zinc is used to galvanize iron to protect it from rusting. In this process, a thin layer of zinc is coated on the surface of iron. Zinc acts as a barrier against corrosion so that iron does not come in contact with water or moisture in the air.

Question 25.
Name the metal which is used to make thin foils for packaging medicines, chocolates, and food items, etc.
Answer:
Aluminium is used to make thin foils for packaging medicines, chocolates and food items. This is because it provides a complete barrier to light, oxygen, moisture and bacteria.

Question 26.
Name two metals which are used to make jewellery.
Answer:
Gold and silver are used to make jewellery. This is because these metals are attractive due to their luster and rarity. These metals do not tarnish or react with air.

Question 27.
Where is iron present in our body?
Answer:
Iron is a very important component of haemoglobin in our body. Haemoglobin is the substance in red blood cells that carries oxygen from our lungs and transports it throughout our body.

Question 28.
Name the non-metal which is essential for maintaining life and inhaled during breathing.
Answer:
Oxygen is the nonmetal which is essential for maintaining life and is inhaled during breathing. Oxygen is brought into our lungs via breathing. It is then transported by red blood cells to the entire body to be used to produce energy.

Question 29.
Name one non-metal used for making fertilizers.
Answer:
Phosphorus is used in making fertilizers.

Question 30.
Which non-metal is used in water purification process to make drinking water supply germ-free?
Answer:
Chlorine is used in water purification process to make drinking water supply germ-free. Chlorine kills pathogens such as bacteria and viruses by breaking the chemical bonds in their molecules.

Question 31.
Name the non-metal used to make purple coloured solution which is applied on cuts and wounds as an antiseptic.
Answer:
Iodine is used to make purple coloured solution which is applied on cuts and wounds as an antiseptic. It is used in the treatment and prevention of wound infection.

Question 32.
Name two non-metals which are used in fireworks (crackers, etc.)
Answer:
Sulphur and sodium are used in fire crackers. Fireworks contains metal salts and metal oxides which react to produce an array of colours.

Question 33.
Which non-metals is used as a fuel?
Answer:
Carbon is used as a fuel in the form of coke or charcoal.

Question 34.
State whether the following statements are true or false?
(a) All metals exist in solid form at room temperature.
(b) Coal can be drawn into wires.
(c) Non-metals react with dilute acids to produce hydrogen gas.
(d) Sodium is a very reactive metal.
(e) Copper displaces zinc from zinc sulphate solution.
(f) Rust formed on iron objects is basic in nature.
(g) Non-metals react with water to form a gas which burns with a ‘pop’ sound.
Answer:
(a) False
The metal which is liquid at room temperature is Mercury(Hg). Another metal called Gallium also exists as liquid at room temperature.
(b) False
Coal is made up of carbon. Carbon is a nonmetal. It is non-malleable and non-ductile; hence, coal cannot be drawn into wires.
(c) False
Metals react with dilute acids to form metallic salts and hydrogen gas. For example, zinc reacts with dilute hydrochloric acid to form zinc chloride and hydrogen gas.
(d) True
Sodium is a very reactive metal. It can even react with the moisture in the air. The reaction of sodium with water is exothermic. It produces a lot of heat.
(e) False
Copper is less reactive than zinc. It is placed below zinc in the reactivity series of metals. Hence, copper cannot displace zinc from zinc sulphate solution.
(f) True
Rust is a chemically known as iron oxide. Metal oxides are basic in nature. Since, rust is a metal oxide, it will be basic in nature.
(g) False
Metals react with water to produce hydrogen gas. For example, sodium reacts with water to form sodium hydroxide and hydrogen gas.

Question 35.
Fill in the following blanks with suitable words:
(a) Metals are……………. conductors of heat and………………
(b) Most non-metals are……………. conductors of heat and electricity.
(c) Phosphorous is a very……………. Non-metal.
(d) Metals react with acids to produce………… gas.
(e) Iron is more…………. than copper.
(f) Metals form………oxides whereas non-metals form………oxide.
(g) Sulphur forms………oxide whereas magnesium forms……………oxide.
(h) A non-metal is used to make an antiseptic solution called tincture……………
Answer:
(a) good; electricity
Metals are used to make wires because they are good conductors of electricity. Due to good conductors of heat, metals are used to make utensils.
(b) poor
Non- metals do not have free electrons; hence, they are non-conductors of heat and electricity.
(c) reactive
Phosphorus cannot be kept open in the air because it combines with oxygen so easily that it catches fire automatically. For safety, phosphorus is stored under water in chemical laboratories.
(d) hydrogen.
Metals react with dilute acids to form metallic salts and hydrogen gas. For example, zinc reacts with dilute hydrochloric acid to form zinc chloride and hydrogen gas.
(e) reactive
Iron is more reactive than copper. For example, if we put Iron nail into copper sulphate solution. Iron nail will displace copper from copper sulphate solution.
(f) basic; acidic
Metallic oxides are basic because they react with water to form bases. Nonmetals react with oxygen to form nonmetallic oxides which are acidic in nature because they react with water to form acids.
(g) acidic; basic
Metallic oxides are basic because they react with water to form bases. Nonmetals react with oxygen to form nonmetallic oxides which are acidic in nature because they react with water to form acids.
(h) iodine
Iodine is used to make purple coloured solution which is applied on cuts and wounds as an antiseptic. It is used in the treatment and prevention of wound infection.

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Question 36.
State two physical properties on the basis of which metals can be distinguish from non-metals.
Answer:
The two physical properties on the basis of which metals can be distinguished from non-metals are Malleability and Ductility.

The property of metals which allows metals to be hammered into thin sheets is called Malleability. Due this unique property, metals can be flattened into thin sheets by hammering and rolling.

The property of metals which enables them to be drawn into wires is called Ductility. Due to this property metals can be stretched without breaking and drawn into thin wires. For example, Aluminium and copper are examples of highly ductile metals.

Question 37.
Name the gas produced when aluminium foil reacts with:
(a) dilute hydrochloric acid.
(b) Sodium Hydroxide solution.
Answer:
When aluminium foil reacts with sodium hydroxide, sodium aluminate is formed. Metals react with dilute acids to form metallic salts and hydrogen gas. For example, Aluminium foil reacts with dilute hydrochloric acid to produce aluminium chloride and hydrogen gas.
The balanced chemical equation for the reaction is:
2Al(s) + 6HCl(aq) 2AlCl3(aq) + 3H2(g).
Aluminium is an amphoteric metal. It reacts with both acids and bases. The reaction is highly exothermic and produces a lot of heat. There is rapid evolution of hydrogen gas during this reaction.

Question 38.
State any two physical properties for believing that aluminium is a metal.
Answer:
Aluminium is highly malleable and ductile. Due to this property, aluminium is used in the production of utensils and wire. Aluminium is a good conductor of heat which makes it ideal for making utensils.

Question 39.
Compare the properties of metals and nonmetals with respect to:

1. malleability
2. ductility and
3. conduction of heat and electricity

Answer:
The property of metals which allows metals to be hammered into thin sheets is called Malleability. Due this unique property, metals can be flattened into thin sheets by hammering and rolling.

The property of metals which enables them to be drawn into wires is called Ductility. Due to this property metals can be stretched without breaking and drawn into thin wires. For example, Aluminium and copper are examples of highly ductile metals.

Metals have free electrons which makes them good conductors of heat and electricity. Non- metals do not have free electrons, hence, they are nonconductors of heat and electricity.

Properties	Metals	Nonmetals
Malleability	Metals are highly malleable.	Nonmetals do not have malleability.
Ductility	Metals are highly ductile.	Nonmetals do not have ductility.
Conduction of heat and electricity	Good conductors of heat and electricity.	Poor conductors of heat and electricity.

Question 40.
Give reason why.
(a) Copper metals used for making electric wires.
(b) Graphite is used for making electrode in a cell.
(c) Immersion rods for heating liquids are made of metallic substances.
Answer:
(a) Copper metal is used for making electric wires because it is highly ductile in nature. It is a good conductor of electricity.
The property of metals which enables them to be drawn into wires is called Ductility. Due to this property metals can be stretched without breaking and drawn into thin wires. Metals have free electrons which makes them good conductors of heat and electricity.
(b) Graphite is a good conductor of electricity. Graphite is made of carbon. Its valence electrons are free to move. As a result, graphite is able to conduct electricity which makes it useful for making electrode in a cell.
(c) Immersion rods for heating liquids are made of metallic substances because metallic substances are good conductors of electricity and heat. Metals have free electrons which makes them good conductors of heat and electricity.

Question 41.
Define (a) malleability, and (b) ductility.
Answer:
(a) Malleability: The property of metals which allows metals to be hammered into thin sheets is called Malleability. Due this unique property, metals can be flattened into thin sheets by hammering and rolling.

(b) Ductility: The property of metals which enables them to be drawn into wires is called Ductility. Due to this property metals can be stretched without breaking and drawn into thin wires.

Question 42.
What is meant by saying that metals are:

1. Malleable
2. Ductile
3. Lustrous and
4. Sonorous

Answer:

1. The property of metals which allows metals to be hammered into thin sheets is called Malleability. Due this unique property, metals can be flattened into thin sheets by hammering and rolling. For example, aluminium due to its high ductility, it can be changed into thin sheets to make aluminium foil.
2. The property of metals which enables them to be drawn into wires is called Ductility. Due to this property metals can be stretched without breaking and drawn into thin wires. For example, Copper metal is used for making electric wires because it is highly ductile in nature.
3. Metals have quality to reflect light. As a result, metals are lustrous in nature. It makes metals attractive due to their luster and rarity. Hence, metals like, gold and silver are used to make jewellery. These metals do not tarnish or react with air.
4. Metals are sonorous because they produce a unique sound when something hard strikes their surface. As a result, metals are used in making bells or gongs.

Question 43.
There are two boxes, one made of metal and the other made of wood, which are similar in appearance. How will you find out which box is made of metal?
Answer:
The box made of metal can be identified by striking hard on its surface. Metals are sonorous because they produce a unique sound when something hard strikes their surface. The box which is made of metal will produce a sound on striking its surface.

Question 44.
Consider the following materials:
Copper, Sulphur, Phosphorus, Carbon (such as: pencil lead), Gold, Silver: Which of these materials are: Malleable and ductile; and brittle.
Answer:
Copper, gold and silver are Malleable and ductile because these are metals. The property of metals which allows metals to be hammered into thin sheets is called Malleability. Due this unique property, metals can be flattened into thin sheets by hammering and rolling. The property of metals which enables them to be drawn into wires is called Ductility. Due to this property metals can be stretched without breaking and drawn into thin wires. All of these metals can be used to make wires and sheets.

Sulphur, phosphorous and carbon are brittle. These are nonmetals and cannot be rolled into wires or drawn into sheets.

Question 45.
Can you hold a hot metallic pan which is without a plastic or a wooden handle? Give reason for your Answer:.
Answer:
It is difficult to hold a metallic pan without a plastic or wooden handle. This is because it will result into burning of fingers or hand due to high heat. If the metallic pan has a wooden handle, it will help to hold it. Wood is made of nonmetal which is a poor conductor of heat. Hence, wooden handle is very useful in metallic pan.

Question 46.
The screw driver used by an electrician has a plastic or wooden handle. Why?
Answer:
Screwdriver is made of metal which is a good conductor of electricity. In order to prevent electric shocks by the screw driver its handle is made of wood. Wood is a poor conductor of electricity which protects from electric shocks and makes the screw driver safe from electric shocks.

Question 47.
What is the nature (acidic/basic) of the following oxides?
(a) Magnesium oxide
(b) Sulphur dioxide
Given reason for your choice.
Answer:
Magnesium is a metal. Metals react with oxygen to form metallic oxides. These Hence, Magnesium oxides are basic in nature. On the other hand, nonmetals react with oxygen to form nonmetallic oxides. These oxides differ from metallic oxides because they are acidic in nature. Nonmetallic oxides react with water to form acids. Therefore, Sulphur dioxide is acidic in nature. Magnesium oxide is basic in nature.

Question 48.
What type of oxides are formed:
(a) when metals combine with oxygen?
(b) when non-metals combine with oxygen?
Answer:
(a) Metals react with oxygen to form metallic oxides. These metallic oxides are basic because they react with water to form bases. For example, Magnesium is a metal and magnesium oxide is basic in nature.

(b) Nonmetals react with oxygen to form nonmetallic oxides. These oxides differ from metallic oxides because they are acidic in nature. Nonmetallic oxides react with water to form acids. For example, Sulphur is a nonmetal. Sulphur dioxide is acidic in nature.

Question 49.
Element A is soft, brittle and does not conduct electricity. Element B is hard, malleable and ‘ductile; and also conducts electricity. Which of the two elements, A or B, is a non-metal?
Answer:
Element A is a nonmetal. Since, it is soft and brittle in nature.
Element B is a metal because it is malleable and ductile and it also conducts electricity. The property of metals which allows metals to be hammered into thin sheets is called Malleability. Due this unique property, metals can be flattened into thin sheets by hammering and rolling. The property of metals which enables them to be drawn into wires is called Ductility. Due to this property metals can be stretched without breaking and drawn into thin wires. All of these metals can be used to make wires and sheets.

Question 50.
Consider the following elements:
Sodium, Sulphur, Carbon, Magnesium
Which of these elements will form:
(a) acidic oxides.
(b) Basic oxides.
Answer:
(a) Carbon and Sulphur will form acidic oxides. Nonmetals react with oxygen to form nonmetallic oxides. These oxides differ from metallic oxides because they are acidic in nature. Nonmetallic oxides react with water to form acids. Therefore, oxides of sulphur and carbon i.e. sulphur dioxide and carbon dioxide are acidic in nature.

(b) Sodium and magnesium oxides will be basic in nature. Metals react with oxygen to form metallic oxides. These metallic oxides are basic because they react with water to form bases.

Question 51.
What happens when a copper vessel is exposed to moist air for a long time?
Answer:
When copper vessel is exposed to moist air for a long time it develops a green layer on its surface. Copper corrodes by oxidation in which it reacts with oxygen in the air to form copper oxide. Copper oxide then combines with carbon dioxide to make copper carbonate, which gives it a green colour. This process is called corrosion of copper.
The green material is a mixture of copper hydroxide (Cu(OH)2) and copper carbonate (CuCO3). The following is the reaction
2Cu + H2O + CO2 + O2 → Cu (OH)2 + CuCO3moist air

Question 52.
When a copper object is exposed to moist air for a long t e, then a green coating is formed on its surface.
(a) What is the material of the green coating?
(b) State whether the green coating is acidic or basic.
Answer:
(a) When copper vessel is exposed to moist air for a long time it develops a green layer on its surface. Copper corrodes by oxidation in which it reacts with oxygen in the air to form copper oxide. Copper oxide then combines with carbon dioxide to make copper carbonate, which gives it a green colour. This process is called corrosion of copper. The green material is a mixture of copper hydroxide (Cu(OH)2) and copper carbonate (CuCO3). The following is the reaction
2Cu + H2O + CO2 + O2 → Cu(OH)2 + CuCO3moist air

(b) The green coating will be basic in nature. Green coating is made of copper oxide which is an oxide of metal. Metals react with oxygen to form metallic oxides. These metallic oxides are basic because they react with water to form bases.

Question 53.
Sodium metal reacts vigorously with water.
(a) Name the gas evolved when sodium reacts with water.
(b) State whether the solution formed by the reaction of sodium with water is acidic or basic.
Answer:
(a) Metals react with water to produce hydrogen gas. Sodium reacts with water to form sodium hydroxide and hydrogen gas. Sodium is a highly reactive metal. It even reacts with the moisture present in air. The reaction of sodium with water is highly exothermic in nature. It produces a lot of heat energy and this heat energy can cause the hydrogen gas produced during the reaction, to catch fire. In order to keep it safe, sodium metal is stored in kerosene.

(b) Metals reacts with water to form metal hydroxides and hydrogen gas. These metallic hydroxides are basic. Sodium reacts with water to form sodium hydroxide and hydrogen gas. Sodium hydroxide is basic in nature.

Question 54.
How do metals react with dilute acids? Explain with the help of an example.
Answer:
Metals react with dilute acids to form metallic salts and hydrogen gas. For example, Aluminium foil reacts with dilute hydrochloric acid to produce aluminum chloride and hydrogen gas.
The balanced chemical equation for the reaction is:
2Al(s) + 6HCl(aq) 2AlCl3(aq) + 3H2(g).

Question 55.
What would you observe when a strip of zinc is placed in copper sulphate solution? Write a word equation of the reaction which takes place.
Answer:
When a strip of zinc is placed in copper sulphate solution it will displace copper from copper sulphate solution. Zinc is placed above copper in reactivity series of metal. Hence, it will be able to replace copper from copper sulphate solution.
Zinc + Copper Sulphate ➝ Copper + Zinc sulphate

Question 56.
Can copper displace iron from iron sulphate solution? Give reason for your answer.
Answer:
Copper cannot displace iron from iron sulphate solution. Copper is less reactive than iron. Iron is placed above the copper in reactivity series of metals. Therefore, copper cannot displace iron from iron sulphate solution. But if we put Iron nail into copper sulphate solution. Iron nail will displace copper from copper sulphate solution.

Question 57 A.
Name one metal which can displace iron from iron sulphate solution.
Answer:
Zinc is placed above iron in the reactivity series of metals. Hence, zinc will be able to displace iron for iron sulphate solution.

Question 57 B.
Name one metal which cannot displace iron from iron sulphate solution.
Answer:
Copper cannot displace iron from iron sulphate solution. Copper is less reactive than iron. Iron is placed above the copper in reactivity series of metals. Therefore, copper cannot displace iron from iron sulphate solution.

Question 58.
Can you store lemon pickle in an aluminium utensil? Explain.
Answer:
Lemon pickle is acidic in nature. Aluminium metal is highly reactive in nature. If the pickle is stored in an aluminium container, the acid present in pickle will react with aluminium and the pickle will be spoiled.
Hence, we cannot store lemon pickle in aluminium container.

Question 59.
Why should the foodstuffs like orange juice, pickles, chutney and curd not be kept in iron or aluminium containers?
Answer:
Food stuff like orange juice, pickles, chutney and curd are acidic in nature. Iron and aluminium are highly reactive metals. If any of this stuff is stored in iron or aluminium container the acid inside these food stuffs will react with iron or aluminium to produce toxins. Hence, we cannot store foodstuffs like orange juice, pickles, chutney and curd not be kept in iron or aluminium containers.

Question 60.
Give reasons for the following:
(a) Sodium and potassium are stored in kerosene.
(b) Copper cannot displace zinc from its salt solution (zinc sulphate solution).
Answer:
(a) Metals react with water to produce hydrogen gas. Sodium reacts with water to form sodium hydroxide and hydrogen gas. Similarly, potassium also reacts with water to potassium hydroxide and hydrogen gas. Both Sodium and potassium are highly reactive metals. They can even react with the moisture present in air. The reaction of sodium and potassium with water is highly exothermic in nature. It produces a lot of heat energy and this heat energy can cause the hydrogen gas produced during the reaction, to catch fire. In order to keep it safe, sodium and potassium are stored in kerosene.

(b) Copper cannot displace zinc from zinc sulphate solution. Zinc is placed above copper in reactivity series of metal. Hence, it will be able to replace copper from copper sulphate solution.
Zinc + Copper Sulphate ➝ Copper + Zinc sulphate

Question 61 A.
Why are metals used for making bells?
Answer:
Metals are sonorous because they produce a unique sound when something hard strikes their surface. As a result, metals are used in making bells or gongs.

Question 61 B.
Why is phosphorus kept under water?
Answer:
Metals react with water to produce hydrogen gas. Phosphorus cannot be kept open in the air because it combines with oxygen so easily that it catches fire automatically. For safety, phosphorus is stored under water in chemical laboratories.

Question 62.
Which of the following can be beaten into thin sheets? Why?
(a) Zinc
(p) Phosphorus
(c) Sulphur
(d) Oxygen
Answer:
The correct Answer: is (a).
Zinc is metal and it can be beaten into thin sheets. The property of metals which allows metals to be hammered into thin sheets is called Malleability.

Question 63.
Match the substances given in column A with their uses given in column B:
Column A
(i) Gold
(ii) Iron
(iii) Aluminium
(iv) Carbon
(v) Copper
(vi) Mercury
Column B
(a) Thermometers
(b) Electric wires
(c) Wrapping food
(d) Jewellery
(e) Machinery
(f) Fuel
Answer:
(i) Gold – (d) Jewellery
Gold is used to make jewellery. This is because these metals are attractive due to their luster and rarity. These metals do not tarnish or react with air.
(ii) Iron – (e) Machinery
Iron is a very strong metal. It is highly malleable and ductile and hence, can be changed into desired shapes.
(iii) Aluminium – (c) Wrapping food
Aluminium is used to make thin foils for packaging medicines, chocolates and food items. This is because it provides a complete barrier to light, oxygen, moisture and bacteria.
(iv) Carbon – (f) Fuel
Carbon can be used as a fuel in the form of coke and charcoal.
(v) Copper – (b) Electric wires
The property of metals which enables them to be drawn into wires is called Ductility. Due to this property metals can be stretched without breaking and drawn into thin wires. For example, Aluminium and copper are examples of highly ductile metals.
(vi) Mercury – (a) Thermometers
Mercury is used for making thermometers. It is liquid at room temperature and is a very good conductor of heat. Even a slightest change in temperature can be noted by using mercury.

Question 64.
Give one use each of the following metals:
(a) Iron
(b) Copper
(c) Aluminium
(d) Zinc
(e) Mercury
Answer:
(a) Iron is used for making machinery and heavy equipment.
(b) The copper is used in making electric wires because it is a good conductor of electricity.
(c) Aluminium is used to make thin foils for packaging medicines, chocolates and food items. This is because it provides a complete barrier to light, oxygen, moisture and bacteria.
(d) Zinc is widely used in the manufacture of many products such as paints, rubber, cosmetics, pharmaceuticals, plastics, inks, soaps, batteries, textiles and electrical equipment.
(e) Mercury is used for making thermometers. It is liquid at room temperature and is a very good conductor of heat. Even a slightest change in temperature can be noted by using mercury.

Question 65.
State one use each of the following non-metals:
(a) Oxygen
(b) Nitrogen
(c) Sulphur
(d) Chlorine
(e) Iodine
Answer:
(a) Oxygen is the nonmetal which is essential for maintaining life and is inhaled during breathing. Oxygen is brought into our lungs via breathing. It is then transported by red blood cells to the entire body to be used to produce energy.
(b) It can be used to replace air which helps to reduce or eliminate oxidation of materials. It is also used to make fertilizers and explosives.
(c) It is used for making fire crackers.
(d) Chlorine is used in water purification process to make drinking water supply germ-free. Chlorine kills pathogens such as bacteria and viruses by breaking the chemical bonds in their molecules.
(e) Iodine is used to make purple colored solution which is applied on cuts and wounds as an antiseptic. It is used in the treatment and prevention of wound infection.

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Question 66 A.
What are metals? Name five metals.
Answer:
Metals are the elements which lose electrons to form cations and are electropositive in nature. For example, Sodium, potassium, Iron, Zinc and Calcium are metals. Metals are good conductors of heat and electricity. Metals are highly malleable and ductile. The property of metals which allows metals to be hammered into thin sheets is called Malleability. Due this unique property, metals can be flattened into thin sheets by hammering and rolling. The property by which iron metal can be hammered to make objects of different shapes such as axe, spade etc. is called Malleability. As a result of high malleability, iron can be flattened or beaten into thin sheets and desired objects can be made by using it. Sodium, Potassium, Copper, Aluminium, Mercury and sodium are metals.

Question 66 B.
What are non-metals? Name five non-metals.
Answer:
Nonmetals are the elements that gain electrons and form negative ions. They are also called electronegative elements. For example, chlorine, sulphur, oxygen, bromine, phosphorus and nitrogen are nonmetals. Nonmetals are not malleable and ductile but they are brittle. Nonmetals are bad conductors of heat and electricity. They have low melting and boiling points and are soft. Sulphur, Oxygen, Nitrogen, Fluorine and Chlorine are nonmetals.

Question 67 A.
What are metalloids? Name two metalloids.
Answer:
The elements whose properties are intermediate between the properties of metals and nonmetals are called Metalloids. For example, Boron, Silicon and Germanium are metalloids. Heat and electricity can pass through metalloids but not as easily as in metals. Metalloids are also called semiconductors.

Question 67 B.
Classify the following elements into metals, nonmetals and metalloids:
Copper, Sulphur, Aluminium, Oxygen, Silicon, Nitrogen, Germanium, Mercury, Chlorine, Sodium.
Answer:
Metals: Metals are the elements which lose electrons to form cations and are electropositive in nature. For example, Sodium, potassium, Iron, Zinc and Calcium are metals. Metals are good conductors of heat and electricity. Metals are highly malleable and ductile.
Copper, Aluminium, Mercury and sodium are metals.

Nonmetals: Nonmetals are the elements that gain electrons and form negative ions. They are also called electronegative elements. For example, chlorine, sulphur, oxygen, bromine, phosphorus and nitrogen are nonmetals. Nonmetals are not malleable and ductile but they are brittle. Nonmetals are bad conductors of heat and electricity. They have low melting and boiling points and are soft.
Sulphur, Oxygen, Nitrogen and Chlorine are nonmetals.

Metalloids: The elements whose properties are intermediate between the properties of metals and nonmetals are called Metalloids. For example, Boron, Silicon and Germanium are metalloids. Heat and electricity can pass through metalloids but not as easily as in metals. Metalloids are also called semiconductors.
Silicon and Germanium are metalloids.

Question 68 A.
What happens when sulphur dioxide is dissolved in water? Write a word equation for the reaction which takes place.
Answer:
When sulphur dioxide is dissolved in water, then it forms sulphurous acid (H2SO3).
Explanation: Metals react with oxygen to form metallic oxides. These metallic oxides are basic in nature because they react with water to form bases. On the other hand, non-metals react with oxygen to form non-metallic oxides and these oxides differ from metallic oxides because they are acidic in nature. Also, non-metallic oxides react with water to form acids.
Sulphur is non-metal, and sulphur dioxide (SO2) is acidic in nature. Thus, it reacts with water to form sulphurous acid (H2SO3 or H2O.SO2)
The chemical reaction is: SO2 + H2O → H2SO3

Question 68 B.
What happens when an iron nail is placed in copper sulphate solution? Write word equation of the reaction involved.
Answer:
If we put Iron nail into copper sulphate solution, the iron nail will displace copper from copper sulphate solution. The following changes will be observed:
i) The colour of copper sulphate changes from blue to green after putting iron nails in it.
ii) Reddish brown colour is deposited on the iron nails. This reddish brown colour is of copper.
Because (Fe) is more reactive than copper (Cu) and is placed above copper in reactivity series of metals, thus and it changes into iron sulphate and copper.
The chemical reaction is given below: Fe (Iron) + CuSO4 (Copper Sulphate) → FeSO4 (Iron Sulphate) + Cu (Copper)

Question 69 A.
State five characteristics of metals and five characteristics of nonmetals.
Answer:
Metals are the elements which lose electrons to form cations and are electropositive in nature. For example, Sodium, potassium, Iron, Zinc and Calcium are metals. Following are characteristics of metals:

1. Metals are good conductors of heat and electricity.
2. Metals are highly malleable and ductile.
3. They have very high melting and boiling points.
4. Metal oxides are basic in nature.
5. Metals displace hydrogen from dilute acids.

Nonmetals: Nonmetals are the elements that gain electrons and form negative ions. They are also called electronegative elements. For example, chlorine, sulphur, oxygen, bromine, phosphorus and nitrogen are nonmetals. Following are the characteristics of nonmetals:

1. Nonmetals are not malleable and ductile but they are brittle.
2. They are bad conductors of heat and electricity.
3. They have low melting and boiling points and are soft.
4. They form acidic or neutral oxides when they react with oxygen.
5. Nonmetals do not displace hydrogen with dilute acids.

Question 69 B.
State five uses of metals and five uses of non-metals.
Answer:
The five uses of metals are given below:

1. Used for making machinery and heavy equipment. Ex-Iron.
2. Used in making electric wires because it is a good conductor of electricity. Ex- copper
3. Used to make thin foils for packaging medicines, chocolate, and food items. This is because it provides a complete barrier to light, oxygen, moisture, and bacteria.
4. Used in the manufacture of many products such as paints, rubber, cosmetics, pharmaceuticals, plastics, inks, soaps, batteries, textiles and electrical equipment.
5. Mercury is a liquid metal and is used for making thermometers. It is liquid at room temperature and is a very good conductor of heat.

The five uses of non-metals are given below:

1. Used for making fire crackers.
2. Oxygen is an essential non-metal for life. It helps in maintaining life and is inhaled during breathing.
3. Chlorine is used in water purification process to make drinking water supply germ-free. Chlorine kills pathogens such as bacteria and viruses by breaking the chemical bonds in their molecules.
4. Iodine is a non-metal. It is used to make purple coloured solution which is applied on cuts and wounds as an antiseptic.
5. Nitrogen is also a non-metal is used to make fertilizers and explosives.

Question 70.
Compare the Chemical Properties of Metals and Non metals in tabular form.
Answer:
Metals are the elements which lose electrons to form cations and are electropositive in nature. For example, Sodium, potassium, Iron, Zinc and Calcium are metals. Metals are good conductors of heat and electricity. Metals are highly malleable and ductile.

Nonmetals are the elements that gain electrons and form negative ions. They are also called electronegative elements. For example, chlorine, sulphur, oxygen, bromine, phosphorus and nitrogen are nonmetals. Nonmetals are not malleable and ductile but they are brittle. Nonmetals are bad conductors of heat and electricity. They have low melting and boiling points and are soft. Following are the difference in chemical properties between metals and nonmetals.

Nonmetals	Metals
1. Nonmetals form acidic or neutral oxides when they react with oxygen.	1. Metals react with oxygen to form metal oxides which are basic in nature
2. Nonmetals do not displace hydrogen with dilute acids	2. Metals displace hydrogen from dilute acids
3. Nonmetals do not react with water and steam.	3. Metals react with water and steam.
4. Nonmetals form negative ions.	4. Metals form positive ions.

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Question 71.
An element is soft and can be cut easily with a knife. It is very reactive and cannot be kept open in the air. It reacts vigorously with water. This element is most likely to be:
A. magnesium
B. potassium
C. phosphorous
D. aluminium
Answer:
B. potassium
Potassium reacts with water to potassium hydroxide and hydrogen gas. The reaction potassium with water is highly exothermic in nature. It produces a lot of heat energy and this heat energy can cause the hydrogen gas produced during the reaction, to catch fire. In order to keep it safe potassium is stored in kerosene.

Question 72.
Which one of the following four metals would be displaced from the solution of its salt by the other three metals?
A. zinc
B. silver
C. copper
D. magnesium
Answer:
B. silver
Silver is less reactive than zinc, copper and magnesium. It is below all these metals in the reactivity series of metals.

Question 73.
Sulphur element is said to be:
A. ductile
B. hard
C. malleable
D. brittle
Answer:
D. brittle
Sulphur is a nonmetal. It cannot be drawn into wires or changed into sheets. It is very soft and hence, is brittle in nature.

Question 74.
An element Z reacts with water to form a solution which turns phenolphthalein indicator pink. The element X is most likely to be:
A. Sulphur
B. sodium
C. carbon
D. silicon
Answer:
B. sodium
Phenolphthalein is an indicator used in acid-base titrations. It turns colorless in acidic solutions and pink in basic solutions. Sodium is a metal which reacts with water to form sodium hydroxide, which is a base. Hence, phenolphthalein turns the solution pink.

Question 75.
The non-metal which exists in the liquid state at room temperature is:
A. fluorine
B. chlorine
C. bromine
D. iodine
Answer:
C. bromine
Bromine is the nonmetal which is a red-brown liquid at room temperature. It evaporates readily to form a similarly coloured gas.

Question 76.
A basic oxide will be formed by the element:
A. sulphur
B. phosphorus
C. potassium
D. carbon
Answer:
C. potassium
Potassium is a metal. Metallic oxides are basic in nature.

Question 77.
“Is malleable and ductile”. This best describes:
A. a metal
B. a compound
C. a non-metal
D. a mixture
Answer:
A. a metal
The property of metals which allows metals to be hammered into thin sheets is called Malleability. Due this unique property, metals can be flattened into thin sheets by hammering and rolling.

Question 78.
The metal which will not produce hydrogen gas on reacting with dilute sulphuric acid is:
A. sodium
B. silver
C. iron
D. zinc
Answer:
B. silver
Silver is least reactive will not produce hydrogen gas with sulphuric acid.

Question 79.
The element which is stored under kerosene is:
A. sulphur
B. phosphorous
C. sodium
D. silicon
Answer:
C. sodium
Sodium is stored in kerosene because it is highly reactive and it even reacts with moisture from air and catches fire.

Question 80.
Which of the following pairs cannot undergo displacement reaction?
A. iron sulphate solution and magnesium
B. zinc sulphate solution and iron
C. zinc sulphate solution and calcium
D. silver nitrate solution and copper
Answer:
C. zinc sulphate solution and calcium
Zinc sulphate solution and calcium cannot undergo displacement reaction.
This is because zinc is more reactive than iron. Hence, iron cannot displace zinc from zinc sulphate solution.

Question 81.
Which of the following metal exists in the liquid state at room temperature?
A. magnesium
B. manganese
C. mercury
D. sodium
Answer:
C. mercury
Mercury is used for making thermometers. It is liquid at room temperature and is a very good conductor of heat.

Question 82.
The element Z burns in air to form an oxide. The aqueous solution of this oxide turns blue litmus to red. The element Z is most likely to be:
A. carbon
B. calcium
C. iron
D. magnesium
Answer:
A. carbon
Carbon is a nonmetal. Nonmetals form oxides which are acidic in nature. Oxide of carbon is acidic and hence, its aqueous solution will turn blue litmus to red.

Question 83.
Which of the following element is a metalloid?
A. sodium
B. sulphur
C. silicon
D. silver
Answer:
C. silicon
Silicon is a metalloid. The elements whose properties are intermediate between the properties of metals and nonmetals are called Metalloids.

Question 84.
Which of the following elements will produce an oxide that will dissolve in water to form an acid?
A. carbon
B. calcium
C. chromium
D. copper
Answer:
A. carbon
Carbon is a nonmetal. Nonmetals form oxides which are acidic in nature. Oxide of carbon is acidic.

Question 85.
The least reactive metal among the following is:
A. magnesium
B. lead
C. silver
D. sodium
Answer:
C. silver
Silver is least reactive and is placed below all these metals in reactivity series of metals.

Question 86.
You are given a solution of iron sulphate. Which of the following do you think cannot displace iron from iron sulphate?
A. magnesium
B. calcium
C. copper
D. zinc
Answer:
C. copper
Copper cannot displace iron from iron sulphate solution because copper is less reactive than iron.

Question 87.
When a vessel is exposed to moist air for a long time, then a green coating is formed on its surface. The vessel must be made of:
A. zinc
B. magnesium
C. iron
D. copper
Answer:
D. copper
Copper corrodes by oxidation in which it reacts with oxygen in the air to form copper oxide. Copper oxide then combines with carbon dioxide to make copper carbonate, which gives it a green colour. This process is called corrosion of copper.

Question 88.
Which among the following is the most reactive metal?
A. copper
B. calcium
C. iron
D. magnesium
Answer:
B. calcium
Calcium is the most reactive metal than copper, iron and magnesium. It lies above all of these metals in reactivity series.

Question 89.
The element whose oxide will turn red litmus solution to blue will be:
A. sodium
B. sulphur
C. carbon
D. phosphorus
Answer:
A. sodium
Metals react with oxygen to form metallic oxides. These metallic oxides are basic because they react with water to form bases. Sodium is a metal, its oxide will be basic in nature and it will turn red litmus solution to blue.

Question 90.
Which of the following is not a characteristic property of iron?
A. malleability
B. brittleness
C. ductility
D. sonorousness
Answer:
B. brittleness
Brittleness is not a characteristic property of Iron because it is a metal. Malleability, ductility, and sonorousness are the properties of metals.

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Question 91.
Which of the following reactions will not occur? Why not?
(a) Zinc sulphate + Copper ➝ Copper Sulphate + zinc
(b) Copper Sulphate + Iron ➝ iron Sulphate + copper
Answer:
(a) This reaction will not occur. Zinc is more reactive than copper. Copper will not be able to replace zinc from zinc sulphate solution. A more reactive metal can replace a less reactive metal, but a less reactive one cannot replace a more reactive metal. On the other hand, if we take copper sulphate solution and zinc, then zinc will be able to replace copper from copper sulphate solution. Hence, the above reaction will not take place.

(b) A more reactive metal can replace a less reactive metal, but a less reactive one cannot replace a more reactive metal. This reaction will take place. In this case, Iron is more reactive than copper. In a solution of copper sulphate, iron will react and will be able to displace copper from its solution. In this reaction, iron will change into iron sulphate and copper metal will be produced.

Question 92.
One day Reeta went to a jeweller’s shop with her mother. Her mother gave an old gold jewellery to 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:
When gold jewellery is sent for polishing, it loses weight. While polishing, the outer thin layer of gold which is dull is removed by treatment with a chemical. The chemical treatment of this layer causes a reduction in weight of gold ornaments. This leads to a slight loss in the weight of jewellery.

Question 93.
An element burns in air to form an oxide. The aqueous solution of this oxide turns blue litmus paper red. State whether the element is a metal or nonmetal. Name one such element.
Answer:
The aqueous solution of the oxide turns blue litmus paper red. This means the aqueous solution is acidic in nature. Metals react with oxygen to form metallic oxides. These metallic oxides are basic because they react with water to form bases. On the other hand, nonmetals react with oxygen to form nonmetallic oxides. These oxides are different from metallic oxides because they are acidic in nature. Nonmetallic oxides react with water to form acids. Since, the aqueous solution of this oxide is acidic in nature, the element is a nonmetal. For example, Sulphur is a nonmetal. It will form an oxide called sulphur dioxide which is acidic in nature.

Question 94.
An element burns in air to form an oxide. The aqueous solution of this oxide turns turmeric paper red. State whether the element is a metal or nonmetal. Name one such element.
Answer:
Turmeric is used as a natural indicator. Turmeric is yellow in colour. Turmeric paper turns into red when it is dipped into basic solution. Turmeric paper does not change its colour with acid. The aqueous solution of this oxide turns turmeric paper red. It indicates that the oxide is basic in nature. Metals react with oxygen to form metallic oxides. These metallic oxides are basic because they react with water to form bases. On the other hand, nonmetals react with oxygen to form nonmetallic oxides. These oxides are different from metallic oxides because they are acidic in nature. Nonmetallic oxides react with water to form acids. Hence, the element is a metal. For example, magnesium is a metal, it reacts with oxygen to magnesium oxide, which is basic in nature.

Question 95.
The metal X reacts with dilute hydrochloric acid to form a gas Y. The metal X also reacts with sodium hydroxide solution (on heating) to form the same gas Y. When a lighted matchstick is applied, this gas burns by producing a ‘pop’ sound.
(a) name two metals which could behave like X
(b) Name the gas Y
Answer:
(a) The ‘pop’ sound indicates the presence of hydrogen gas. Metals react with dilute acids to form metallic salts and hydrogen gas. Some metals react with bases to produce hydrogen gas. Generally, non-metals do not react with acids. For example, Aluminium reacts with dilute hydrochloric acid to form Aluminium chloride and hydrogen gas. The balanced chemical equation for the reaction is:
2Al(s) + 6HCl(aq) ➝ 2AlCl3(aq) + 3H2(g).
Aluminium is an amphoteric metal. It reacts with both acids and bases. The reaction is highly exothermic and produces a lot of heat. There is rapid evolution of hydrogen gas during this reaction. Aluminium metal reacts with a base called sodium hydroxide to produce sodium aluminate and hydrogen gas.

(b) The name of the gas is hydrogen.

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