Class 8th Science Term 3 Tamilnadu Board Solution
Evaluation- Which type of coal has a high content of carbon?A. lignite B. peat C. bituminous D.…
- Which type of coal is used in household?A. lignite B. peat C. bituminous coal D.…
- Naphthalene ball is obtained fromA. coal gas B. coke C. coal tar D. liquor ammonia…
- Fuel that is used in jet air craftA. petrol B. petroleum gas C. kerosene D. diesel…
- which of these is a fossil fuel?A. wood B. paper C. petroleum D. phosphorus…
- Fill in the blanks: 1. The expansion of LPG is ___________. 2. LPG is stored in…
- Ram’s family cooks food quickly as they use LPG gas. Murugan family takes a longer time to…
- Find the relevant pair: a) Coal - coal gas; petroleum - b) LPG - propane and butane;…
- Read the following tabular column carefully and decide which fuel we should use for…
- What do you understand by the term carbonisation?
- Point out difference between coal and coke.
- Distinguish between petroleum and petrol.
- The boiling point of three components A, B C of petroleum are 120oC, 70oC , 250OC. If a…
- Coal, petrol, diesel and LPG are the fuels used by now. If they are harnessed completely…
- Types of coal and the percentage of carbon in each type below. Which type should be used…
- Countries like Dubai, Saudi Arabia, Abu Dhabi etc. have become very rich in recent years.…
- Why do millions of people turn off their lights on Earth Hour at 8:30pm (20:30 local time)…
- In ‘A’ we get only ashes whereas in ‘B’ we get charcoal. Give reason.…
- You might have read news items such as the one given below. What are the reasons for the…
- Workers in coal mines use battery operated torch lights instead of lanterns. Find the…
- If we identify the leakage of LPG in our kitchen, what measures should we take?…
- LPG can be lit with a gas lighter whereas wood cannot be lit using a gas lighter, why?…
- Which type of coal has a high content of carbon?A. lignite B. peat C. bituminous D.…
- Which type of coal is used in household?A. lignite B. peat C. bituminous coal D.…
- Naphthalene ball is obtained fromA. coal gas B. coke C. coal tar D. liquor ammonia…
- Fuel that is used in jet air craftA. petrol B. petroleum gas C. kerosene D. diesel…
- which of these is a fossil fuel?A. wood B. paper C. petroleum D. phosphorus…
- Fill in the blanks: 1. The expansion of LPG is ___________. 2. LPG is stored in…
- Ram’s family cooks food quickly as they use LPG gas. Murugan family takes a longer time to…
- Find the relevant pair: a) Coal - coal gas; petroleum - b) LPG - propane and butane;…
- Read the following tabular column carefully and decide which fuel we should use for…
- What do you understand by the term carbonisation?
- Point out difference between coal and coke.
- Distinguish between petroleum and petrol.
- The boiling point of three components A, B C of petroleum are 120oC, 70oC , 250OC. If a…
- Coal, petrol, diesel and LPG are the fuels used by now. If they are harnessed completely…
- Types of coal and the percentage of carbon in each type below. Which type should be used…
- Countries like Dubai, Saudi Arabia, Abu Dhabi etc. have become very rich in recent years.…
- Why do millions of people turn off their lights on Earth Hour at 8:30pm (20:30 local time)…
- In ‘A’ we get only ashes whereas in ‘B’ we get charcoal. Give reason.…
- You might have read news items such as the one given below. What are the reasons for the…
- Workers in coal mines use battery operated torch lights instead of lanterns. Find the…
- If we identify the leakage of LPG in our kitchen, what measures should we take?…
- LPG can be lit with a gas lighter whereas wood cannot be lit using a gas lighter, why?…
Evaluation
Question 1.Which type of coal has a high content of carbon?
A. lignite
B. peat
C. bituminous
D. anthracite coal
Answer:Among all the types of coal, anthracite has maximum content of carbon.
The carbon content in different types of coal is given as:
Question 2.Which type of coal is used in household?
A. lignite
B. peat
C. bituminous coal
D. anthracine coal
Answer:Bituminous Coal is used for household chores.
Question 3.Naphthalene ball is obtained from
A. coal gas
B. coke
C. coal tar
D. liquor ammonia
Answer:Naphthalene is a polycyclic aromatic hydrocarbon (PAH) compound, derived from crude oil or coal tar during steel production.
Question 4.Fuel that is used in jet air craft
A. petrol
B. petroleum gas
C. kerosene
D. diesel
Answer:Kerosene is the fuel used in aircraft.
Petrol or petroleum is not used because it is costly & volatile fuel.
Diesel is not used because of its high freezing point, At higher altitudes, it is very difficult to keep the diesel in liquid form.
Hence, kerosene alongwith gasoline is used as jet aircraft fuel.
Question 5.which of these is a fossil fuel?
A. wood
B. paper
C. petroleum
D. phosphorus
Answer:Fossil fuel is a naturally occurring fuel obtained from the remains dead organisms and vegetation.
Out of the given options, only petroleum is formed from the dead remains. Hence, it is a fossil fuel.
Question 6.Fill in the blanks:
1. The expansion of LPG is ___________.
2. LPG is stored in _____________ form in the gas cylinder.
3. The expansion of CNG is _________________.
4. The chief element in coal is _______________.
5. Natural gas contains mainly ___________________.
6. Heating in the absence of air is called _______________.
7. ______________ is the primary source of energy.
8. The coal obtained in Neyveli is _________.
9. The process of separating individual liquids, from the mixture of liquids which differ in their boiling point is called _____________.
10. ___________ is used as a reducing agent in steel manufacturing.
Answer:1. The expansion of LPG is liquid petroleum gas.
LPG is a hydrocarbon gas used as fuel in heating appliances, cooking equipment, and vehicles.
2. LPG is stored in gas form in the gas cylinder.
It is extracted from crude oil and natural gas. And, it is stored in liquid form under pressure in a steel container or tank.
3. The expansion of CNG is Compressed Natural Gas.
Compressed natural gas (CNG) is a fuel which can be used in place of petrol, diesel fuel and propane/LPG.
4. The chief element in coal is carbon.
Coal is mainly composed of carbon, along with other elements: hydrogen, sulphur, oxygen, and nitrogen.
5. Natural gas contains mainly methane.
Natural gas majorly consists of methane and contains small percentage of carbon dioxide, nitrogen, hydrogen sulphide, or helium.
6. Heating in absence of air is called calcination.
Calcination is a process of heating the ore below its melting point in absence of air whereas, roasting is a process of heating the element in presence of air.
7. Fossil fuels Is the primary source of energy
Fossil fuels, including coal, oil and natural gas, are currently the world's primary energy source.
8. The coal obtained in Neyveli is lignite
Jet is a compact form of lignite that is used as an ormental stone in a polished form.
9. The process of separating individual liquids, from the mixture of liquids which differ in their boiling point is called fractional distillation.
Fractional distillation is the separation of a mixture into its component parts, or fractions
10. Iron oxide is used as a reducing agent in steel manufacturing.
In the process of steel manufacturing, iron is changed into steel by blowing oxygen through the molten metal from the Blast Furnace. This oxidises the impurities in the molten metal.
Question 7.Ram’s family cooks food quickly as they use LPG gas. Murugan family takes a longer time to cook food. What could be the reason?
Answer:The reason for quick cooking in Ram’s house and delayed cooking in Murugan’s house is use of LPG and wood respectively.
i. LPG burns completely and leaves no residue or smoke as it has higher hydrocarbon than wood.
ii. LPG gas catches fire easily and also has high calorific value. While wood is a solid and has low calorific value. Thus, it catches fire slowly.
Question 8.Find the relevant pair:
a) Coal – coal gas; petroleum –
b) LPG – propane and butane; natural gas
c) Diesel – petroleum; bio diesel-
Answer:a) Petrol
Reason: It is analogy relation of natural occurring substance and its product.
b) methane
Reason: It is analogy relation of gas and its constituents.
c) wind energy
Reason: Both are same type of energy fuels.
Question 9.Read the following tabular column carefully and decide which fuel we should use for cooking.
Answer:i. LPG gas is more preferable, because it is safe for human life and environment.
ii. LPG is clean fuel as no smoke is produced.
iii. LPG gas is more beneficial because is catches fire easily and takes less time.
Question 10.What do you understand by the term carbonisation?
Answer:Million years ago, when dead remains of plants got buried deep in soil. Then due to further act of pressure and high temperature, fossils were formed. Coal majorly consists of carbon. The process of conversion of dead plants to coal is called carbonisation.
Question 11.Point out difference between coal and coke.
Answer:
Question 12.Distinguish between petroleum and petrol.
Answer:
Question 13.The boiling point of three components A, B & C of petroleum are 120oC, 70oC , 250OC. If a mixture of these three is fractionally distilled, which of these will be obtained at the bottom of distillation column?
Answer:The lowermost will be of 250oc.
As after, distillation lower most is of highest temperature and at the top lowest temperature component gets accumulated.
Question 14.Coal, petrol, diesel and LPG are the fuels used by now. If they are harnessed completely we would be running short of fuels for cooking and using vehicles and working of factories in our near future. So, we need alternative sources of energy. As young scientist suggests a source of alternative.
Answer:Alternative sources of energy are:
Wind Energy: For wind energy, wind mills are established in the field. When fast air flows then blades rotate and current is generated which is produces electricity.
Biodiesel: It is fuel obtained from various types of oil. Oil like cotton seed, rice bran oil etc. are mainly used.
Solar energy: To generate solar energy solar panels are installed. Radiations from sun fall on these panels, which thus generates energy. This energy is further used in in) solar cookers, ii) solar cells iii) solar water heaters.
Question 15.Types of coal and the percentage of carbon in each type below. Which type should be used to get high heat energy?
Lignite -25to 35 % carbon.
Bituminous 45 to 86% carbon.
Anthracite – 87 to 97% carbon
Answer:The type of coal having high heat energy is anthracite.
As it has highest amount of carbon thus it is clearest form of coal.
Question 16.Countries like Dubai, Saudi Arabia, Abu Dhabi etc. have become very rich in recent years. What could be the reason?
Answer:These countries have become rich in recent years, because oil deposits were discovered here in 1950s. thus these countries started exporting oil thus due to increase in export, wealth started increasing.
Question 17.Why do millions of people turn off their lights on Earth Hour at 8:30pm (20:30 local time) on last Saturday of march every year?
Answer:Every year on this date we switch off lights on earth hour 8:30 to 9:30. This is an initiate towards saving electricity and also spreading awareness among people that resources are scarce and we need to save it.
As together being united, we can save electricity.
Question 18.In ‘A’ we get only ashes whereas in ‘B’ we get charcoal. Give reason.
Answer:In fig A so is because when we burn wood alone, it is leaves only ashes
But in fig B the wood is when covered with clay, then it forms charcoal. as due to covering of clay doesn’t lead to formation of ashes. Charcoal is a useful process.
Question 19.You might have read news items such as the one given below.
What are the reasons for the tragedy? List out the precautionary measures.
Answer:The main reason behind this tragedy is the carelessness towards security of workers.
Precautionary measures:
i) Spreading awareness
ii) Keeping care of workers and other people around it
iii) Using all the products properly.
Question 20.Workers in coal mines use battery operated torch lights instead of lanterns. Find the reason.
Answer:I. Lanterns can catch fire; thus, it is very dangerous. Ii.
II. Whereas, torch lights don’t catch as it has batteries in it. Therefore, it is safer.
Question 21.If we identify the leakage of LPG in our kitchen, what measures should we take?
Answer:Whenever we identify that there is leakage of LPG in kitchen, then certain measures should be taken: -
a. Close the LPG regulator immediately
b. Don’t switch on/off electric switches.
c. Open door and windows to ventilate.
d. Isolate main electrical supply from outside
Question 22.LPG can be lit with a gas lighter whereas wood cannot be lit using a gas lighter, why?
Answer:LPG is a gas. thus, can be lit easily by gas lighter. But wood is a solid. Also, LPG has high calorific value, while wood has high calorific value.
Which type of coal has a high content of carbon?
A. lignite
B. peat
C. bituminous
D. anthracite coal
Answer:
Among all the types of coal, anthracite has maximum content of carbon.
The carbon content in different types of coal is given as:
Question 2.
Which type of coal is used in household?
A. lignite
B. peat
C. bituminous coal
D. anthracine coal
Answer:
Bituminous Coal is used for household chores.
Question 3.
Naphthalene ball is obtained from
A. coal gas
B. coke
C. coal tar
D. liquor ammonia
Answer:
Naphthalene is a polycyclic aromatic hydrocarbon (PAH) compound, derived from crude oil or coal tar during steel production.
Question 4.
Fuel that is used in jet air craft
A. petrol
B. petroleum gas
C. kerosene
D. diesel
Answer:
Kerosene is the fuel used in aircraft.
Petrol or petroleum is not used because it is costly & volatile fuel.
Diesel is not used because of its high freezing point, At higher altitudes, it is very difficult to keep the diesel in liquid form.
Hence, kerosene alongwith gasoline is used as jet aircraft fuel.
Question 5.
which of these is a fossil fuel?
A. wood
B. paper
C. petroleum
D. phosphorus
Answer:
Fossil fuel is a naturally occurring fuel obtained from the remains dead organisms and vegetation.
Out of the given options, only petroleum is formed from the dead remains. Hence, it is a fossil fuel.
Question 6.
Fill in the blanks:
1. The expansion of LPG is ___________.
2. LPG is stored in _____________ form in the gas cylinder.
3. The expansion of CNG is _________________.
4. The chief element in coal is _______________.
5. Natural gas contains mainly ___________________.
6. Heating in the absence of air is called _______________.
7. ______________ is the primary source of energy.
8. The coal obtained in Neyveli is _________.
9. The process of separating individual liquids, from the mixture of liquids which differ in their boiling point is called _____________.
10. ___________ is used as a reducing agent in steel manufacturing.
Answer:
1. The expansion of LPG is liquid petroleum gas.
LPG is a hydrocarbon gas used as fuel in heating appliances, cooking equipment, and vehicles.
2. LPG is stored in gas form in the gas cylinder.
It is extracted from crude oil and natural gas. And, it is stored in liquid form under pressure in a steel container or tank.
3. The expansion of CNG is Compressed Natural Gas.
Compressed natural gas (CNG) is a fuel which can be used in place of petrol, diesel fuel and propane/LPG.
4. The chief element in coal is carbon.
Coal is mainly composed of carbon, along with other elements: hydrogen, sulphur, oxygen, and nitrogen.
5. Natural gas contains mainly methane.
Natural gas majorly consists of methane and contains small percentage of carbon dioxide, nitrogen, hydrogen sulphide, or helium.
6. Heating in absence of air is called calcination.
Calcination is a process of heating the ore below its melting point in absence of air whereas, roasting is a process of heating the element in presence of air.
7. Fossil fuels Is the primary source of energy
Fossil fuels, including coal, oil and natural gas, are currently the world's primary energy source.
8. The coal obtained in Neyveli is lignite
Jet is a compact form of lignite that is used as an ormental stone in a polished form.
9. The process of separating individual liquids, from the mixture of liquids which differ in their boiling point is called fractional distillation.
Fractional distillation is the separation of a mixture into its component parts, or fractions
10. Iron oxide is used as a reducing agent in steel manufacturing.
In the process of steel manufacturing, iron is changed into steel by blowing oxygen through the molten metal from the Blast Furnace. This oxidises the impurities in the molten metal.
Question 7.
Ram’s family cooks food quickly as they use LPG gas. Murugan family takes a longer time to cook food. What could be the reason?
Answer:
The reason for quick cooking in Ram’s house and delayed cooking in Murugan’s house is use of LPG and wood respectively.
i. LPG burns completely and leaves no residue or smoke as it has higher hydrocarbon than wood.
ii. LPG gas catches fire easily and also has high calorific value. While wood is a solid and has low calorific value. Thus, it catches fire slowly.
Question 8.
Find the relevant pair:
a) Coal – coal gas; petroleum –
b) LPG – propane and butane; natural gas
c) Diesel – petroleum; bio diesel-
Answer:
a) Petrol
Reason: It is analogy relation of natural occurring substance and its product.
b) methane
Reason: It is analogy relation of gas and its constituents.
c) wind energy
Reason: Both are same type of energy fuels.
Question 9.
Read the following tabular column carefully and decide which fuel we should use for cooking.
Answer:
i. LPG gas is more preferable, because it is safe for human life and environment.
ii. LPG is clean fuel as no smoke is produced.
iii. LPG gas is more beneficial because is catches fire easily and takes less time.
Question 10.
What do you understand by the term carbonisation?
Answer:
Million years ago, when dead remains of plants got buried deep in soil. Then due to further act of pressure and high temperature, fossils were formed. Coal majorly consists of carbon. The process of conversion of dead plants to coal is called carbonisation.
Question 11.
Point out difference between coal and coke.
Answer:
Question 12.
Distinguish between petroleum and petrol.
Answer:
Question 13.
The boiling point of three components A, B & C of petroleum are 120oC, 70oC , 250OC. If a mixture of these three is fractionally distilled, which of these will be obtained at the bottom of distillation column?
Answer:
The lowermost will be of 250oc.
As after, distillation lower most is of highest temperature and at the top lowest temperature component gets accumulated.
Question 14.
Coal, petrol, diesel and LPG are the fuels used by now. If they are harnessed completely we would be running short of fuels for cooking and using vehicles and working of factories in our near future. So, we need alternative sources of energy. As young scientist suggests a source of alternative.
Answer:
Alternative sources of energy are:
Wind Energy: For wind energy, wind mills are established in the field. When fast air flows then blades rotate and current is generated which is produces electricity.
Biodiesel: It is fuel obtained from various types of oil. Oil like cotton seed, rice bran oil etc. are mainly used.
Solar energy: To generate solar energy solar panels are installed. Radiations from sun fall on these panels, which thus generates energy. This energy is further used in in) solar cookers, ii) solar cells iii) solar water heaters.
Question 15.
Types of coal and the percentage of carbon in each type below. Which type should be used to get high heat energy?
Lignite -25to 35 % carbon.
Bituminous 45 to 86% carbon.
Anthracite – 87 to 97% carbon
Answer:
The type of coal having high heat energy is anthracite.
As it has highest amount of carbon thus it is clearest form of coal.
Question 16.
Countries like Dubai, Saudi Arabia, Abu Dhabi etc. have become very rich in recent years. What could be the reason?
Answer:
These countries have become rich in recent years, because oil deposits were discovered here in 1950s. thus these countries started exporting oil thus due to increase in export, wealth started increasing.
Question 17.
Why do millions of people turn off their lights on Earth Hour at 8:30pm (20:30 local time) on last Saturday of march every year?
Answer:
Every year on this date we switch off lights on earth hour 8:30 to 9:30. This is an initiate towards saving electricity and also spreading awareness among people that resources are scarce and we need to save it.
As together being united, we can save electricity.
Question 18.
In ‘A’ we get only ashes whereas in ‘B’ we get charcoal. Give reason.
Answer:
In fig A so is because when we burn wood alone, it is leaves only ashes
But in fig B the wood is when covered with clay, then it forms charcoal. as due to covering of clay doesn’t lead to formation of ashes. Charcoal is a useful process.
Question 19.
You might have read news items such as the one given below.
What are the reasons for the tragedy? List out the precautionary measures.
Answer:
The main reason behind this tragedy is the carelessness towards security of workers.
Precautionary measures:
i) Spreading awareness
ii) Keeping care of workers and other people around it
iii) Using all the products properly.
Question 20.
Workers in coal mines use battery operated torch lights instead of lanterns. Find the reason.
Answer:
I. Lanterns can catch fire; thus, it is very dangerous. Ii.
II. Whereas, torch lights don’t catch as it has batteries in it. Therefore, it is safer.
Question 21.
If we identify the leakage of LPG in our kitchen, what measures should we take?
Answer:
Whenever we identify that there is leakage of LPG in kitchen, then certain measures should be taken: -
a. Close the LPG regulator immediately
b. Don’t switch on/off electric switches.
c. Open door and windows to ventilate.
d. Isolate main electrical supply from outside
Question 22.
LPG can be lit with a gas lighter whereas wood cannot be lit using a gas lighter, why?
Answer:
LPG is a gas. thus, can be lit easily by gas lighter. But wood is a solid. Also, LPG has high calorific value, while wood has high calorific value.