Combustion And Flame Worksheet

Objective Type Questions

1. Match the list A with the list B:
   
2. Fill in the blanks:
   (a) The most common supporter of combustion is _________.
   (b) Oxides of _________ and nitrogen causes acid rain.
   (c) The _________ zone of a flame is the hottest.
   (d) A good fuel should have _________ calorific value.
   (e) Least polluting fuel for vehicle is __________.
   (f) The increase in amount of _________ gas in atmosphere results in global warming.
   
   
3. State whether the following statements are true or false. In case of false statement, write the correct one.
   (i) Combustion is a physical process in which a material combines with oxygen to produce heat.
   (a) True
   (b) False
   (ii) Global warming is thought to be caused by an increase in the concentration of nitrogen in the atmosphere.
   (a) True
   (b) False
   
   Multiple Choice Questions
   
   
4. Neeta puts a sparkling rod into a candle flame. The faster the rod lights up, the hotter the flame. The given image depicts three distinct zones of a flame Zone 1, Zone 2 and Zone 3.
   
   Which of the following is true?
   (a) Zone 3 is the hottest part of the flame
   (b) Zone 2 is moderately hot part of the flame
   (c) Zone 1 is the least hot part of the flame
   (d) The temperature is the same across all zones.
   
   
5. A substance which reacts with oxygen giving heat is called a combustible substance. Which, one of the following is a combustible substance?
   (a) water
   (b) glass
   (c) stone piece
   (d) wax
   
   
6. The international weather forecast projected El Nino this year. Fire outbreaks in the Australian forest is one of the common event happens in such weather condition which is one of the major cause of deforestation. Forest fires are typically caused by:
   A. Fire in coal mine
   B. Heat of the Sun
   C. Lightning strike
   D. Use of natural gas as fuel
   E. Carelessness of human beings
   (a) A, B and D
   (b) B, C and E
   (c) C, D and E
   (d) A, B and C
   
   
7. Choose the correct statement about inflammable substances from the following. They have:
   (a) low ignition temperature and cannot catch fire easily.
   (b) high ignition temperature and can catch fire easily.
   (c) low ignition temperature and can catch fire easily.
   (d) high ignition temperature and cannot catch fire easily.
   
   
8. The calorific value of a fuel is expressed in a unit as:
   (a) kilojoule per litre
   (b) kilogram per millilitre
   (c) kilojoule per gram
   (d) kilojoule per kilogram
   
   
9. Lowest temperature at which a substance catches fire is known as
   (a) lowest temperature
   (b) burning temperature
   (c) ignition temperature
   (d) flaming temperature
   
   
10. Teacher asked Rohit to list the characteristics of the outermost zone of the flame.  He listed below mentioned characteristics. Which of these statements are true?
    A. It is the coolest zone of the flame.
    B. It is blue coloured zone of the flame.
    C. It is the zone of complete combustion.
    D. Goldsmith uses this zone while making gold jewelry.
    (a) Only C
    (b) Only A
    (c) A, B, and C
    (d) B, C and D
    
    
11. Kasturi read in a news article that, one of the gas generated at a power plant was responsible for harming few people resting there.
    
    Several hazardous gases are produced during the burning of various fuels at power plants, including
    A. Sulphur dioxide
    B. Nitrogen dioxide
    C. Carbon monoxide
    D. Carbon dioxide
    Name the gas from the given list which is generated by incomplete combustion of fuel and can be harmful for a person sleeping in a room.
    (a) Only B
    (b) Only C
    (c) Only A
    (d) Both C and D
    
    
12. Which of the following mentioned gases are responsible for acid rain?
    A. Nitrogen
    B. Oxygen
    C. Sulphur dioxide
    D. Nitrogen oxide
    E. Ozone
    (a) Only C
    (b) A, B and E
    (c) C and D
    (d) A, D and E
    
    Case Study Questions
    
    
13. We find that a combustible substance cannot catch fire or burn as long as its temperature is lower than its ignition temperature. Have you ever seen cooking oil catching fire when a frying pan is kept for a long on a burning stove? Kerosene oil and wood do not catch fire on their own at room temperature. But, if kerosene oil is heated a little, it will catch fire.
    (a) What is meant by ignition temperature?
    (b) How does a matchstick catch fire?
    (c) Priyanka noticed that sodium metal is kept immersed in kerosene the chemistry laboratory. Why is sodium metal kept immersed in kerosene?
    
    
14. Combustion of coal dust has resulted in many disastrous fires in coal mines. Spontaneous forest fires are sometimes due to the heat of the sun or due to lightning strike. However, most forest fires are due to the carelessness of human beings.
    We generally have fireworks on festival days. When a cracker is ignited, a sudden reaction takes place with the evolution of heat, light and sound. Bring a burning matchstick or a gas lighter near a gas stove in the kitchen. Turn on the knob of the gas stove. We find that the gas burns rapidly and produces heat and light.
    (a) What is meant by rapid combustion? Which of the mentioned examples demonstrates this?
    (b) What is meant by explosion? Which of the mentioned examples demonstrates this?
    (c) What is meant by spontaneous combustion? Which of the mentioned examples demonstrates this?
    
    
15. The increasing fuel consumption has harmful effects on the environment. Global warming is the rise in temperature of the atmosphere of the earth. This results, among other things, in the melting of polar glaciers, which leads to a rise in the sea level, causing floods in the coastal areas. Low lying coastal areas may even be permanently submerged under water.
    
    (a) What is meant by global warming? Mention cause for the same.
    (b) Give consequences of global warming.
    (c) Explain acid rain and its consequences.
    
    Subjective Questions
    
    
16. Prathamesh lit a candle and placed a glass over it. He noticed that the candle eventually went out of flame. What could be the cause of this?
    
17. Kiran and his mother went to a goldsmith to get jewellery made from a 24 carat gold coin that his mother had purchased on the occasion of Akshay Tritiya. He noticed the goldsmith blowing in the flame to melt the gold. Which flame zone would a goldsmith employ to melt gold or silver, and why?
    
18. What is meant by “Fuel”? Give examples for the same.
    
    
19. Mention the characteristics of an Ideal fuel.
    
    Assertion Reasoning Questions
    
    Below questions consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:
    
20. Assertion (A): For fires involving electrical equipment and inflammable materials like petrol, carbon monoxide (CO) is the best extinguisher.
    Reason (R): CO₂, being heavier than oxygen, covers the fire like a blanket.
    
    
21. Assertion (A): The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value.
    Reason(R): Calorific value of Cow dung cake is 15000 kJ/kg.
    
    
22. Assertion (A): Food is fuel for our body.
    Reason (R):  Food gives energy to your body to carry out different processes.
    
    
23. Assertion (A): CNG is preferred as automobile fuel over diesel and petrol.
    Reason (R): CNG is a cleaner fuel.
    
    
24. Assertion (A): Carbon fuels like wood, coal cause respiratory diseases, such as asthma.
    Reason (R): People can develop asthma after exposure to things such as pollen, animal fur or feather, etc.

Objective Type Questions

1. Match the list A with the list B:
   
   
   Solution:
   
   
   
2. Fill in the blanks:
   (a) The most common supporter of combustion is _________.
   (b) Oxides of _________ and nitrogen causes acid rain.
   (c) The _________ zone of a flame is the hottest.
   (d) A good fuel should have _________ calorific value.
   (e) Least polluting fuel for vehicle is __________.
   (f) The increase in amount of _________ gas in atmosphere results in global warming.
   
   Solution:
   (a)Oxygen/air
   (b)sulphur
   (c)non-luminous
   (d)high
   (e)CNG (compressed natural gas)
   (f)Carbon dioxide
   
   
3. State whether the following statements are true or false. In case of false statement, write the correct one.
   (i) Combustion is a physical process in which a material combines with oxygen to produce heat.
   (a) True
   (b) False
   (ii) Global warming is thought to be caused by an increase in the concentration of nitrogen in the atmosphere.
   (a) True
   (b) False
   
   (i) Correct option: (b) False.
   Solution: Combustion is a chemical reaction in which a material combines with oxygen to produce heat.
   (ii) Correct option: (b) False
   Solution: Global warming is thought to be caused by an increase in the concentration of carbon dioxide in the atmosphere.
   
   Multiple Choice Questions
   
   
4. Neeta puts a sparkling rod into a candle flame. The faster the rod lights up, the hotter the flame. The given image depicts three distinct zones of a flame Zone 1, Zone 2 and Zone 3.
   
   Which of the following is true?
   (a) Zone 3 is the hottest part of the flame
   (b) Zone 2 is moderately hot part of the flame
   (c) Zone 1 is the least hot part of the flame
   (d) The temperature is the same across all zones.
   
   Correct option: (b) Zone 2 is moderately hot part of the flame.
   Solution: Option a – Incorrect since it is the least hot zone of the flame. Option c – Incorrect since zone 1 is the hottest part of the flame. Option d is certainly incorrect.
   
   
5. A substance which reacts with oxygen giving heat is called a combustible substance. Which, one of the following is a combustible substance?
   (a) water
   (b) glass
   (c) stone piece
   (d) wax
   
   Correct option: (d) wax
   Solution: Water, glass and stone piece do not react with atmospheric oxygen to generate heat while wax reacts with oxygen to form carbon and heat.
   
   
6. The international weather forecast projected El Nino this year. Fire outbreaks in the Australian forest is one of the common event happens in such weather condition which is one of the major cause of deforestation. Forest fires are typically caused by:
   A. Fire in coal mine
   B. Heat of the Sun
   C. Lightning strike
   D. Use of natural gas as fuel
   E. Carelessness of human beings
   (a) A, B and D
   (b) B, C and E
   (c) C, D and E
   (d) A, B and C
   
   Correct option: (b) B, C and E
   Solution: Spontaneous forest fires are sometimes due to the heat of the sun or due to lightning strike. However, most forest fires are due to the carelessness of human beings. It is important to remember that the campfires must be completely extinguished before leaving a forest after a picnic, or a visit.
   
   
7. Choose the correct statement about inflammable substances from the following. They have:
   (a) low ignition temperature and cannot catch fire easily.
   (b) high ignition temperature and can catch fire easily.
   (c) low ignition temperature and can catch fire easily.
   (d) high ignition temperature and cannot catch fire easily.
   
   Correct option: (c) low ignition temperature and catch fire easily.
   Solution: The substances which have very low ignition temperature and can easily catch fire with a flame are called inflammable substances.
   
   
8. The calorific value of a fuel is expressed in a unit as:
   (a) kilojoule per litre
   (b) kilogram per millilitre
   (c) kilojoule per gram
   (d) kilojoule per kilogram
   
   Correct option: (d) because gas and petroleum oil are lighter than sea water and these substances do not mix.
   Solution: The calorific value of a fuel is expressed in a unit is expressed as kilojoule per kilogram. Example: Calorific value of CNG is 50000 kJ/kg.
   
   
9. Lowest temperature at which a substance catches fire is known as
   (a) lowest temperature
   (b) burning temperature
   (c) ignition temperature
   (d) flaming temperature
   
   Correct option: (c) ignition temperature
   Solution: Lowest temperature at which a substance catches fire is known as ignition temperature.
   
   
10. Teacher asked Rohit to list the characteristics of the outermost zone of the flame.  He listed below mentioned characteristics. Which of these statements are true?
    A. It is the coolest zone of the flame.
    B. It is blue coloured zone of the flame.
    C. It is the zone of complete combustion.
    D. Goldsmith uses this zone while making gold jewelry.
    (a) Only C
    (b) Only A
    (c) A, B, and C
    (d) B, C and D
    
    Correct option: (d) B, C and D
    Solution: Outermost zone of the flame is the hottest blue coloured zone where complete combustion takes place.
    
    
11. Kasturi read in a news article that, one of the gas generated at a power plant was responsible for harming few people resting there.
    
    Several hazardous gases are produced during the burning of various fuels at power plants, including
    A. Sulphur dioxide
    B. Nitrogen dioxide
    C. Carbon monoxide
    D. Carbon dioxide
    Name the gas from the given list which is generated by incomplete combustion of fuel and can be harmful for a person sleeping in a room.
    (a) Only B
    (b) Only C
    (c) Only A
    (d) Both C and D
    
    Correct option: (b) Only C
    Solution: Power plants generate electricity by burning fossil fuels. Carbon monoxide is the one which is dangerous and can harm people sleeping in a room.
    
    
12. Which of the following mentioned gases are responsible for acid rain?
    A. Nitrogen
    B. Oxygen
    C. Sulphur dioxide
    D. Nitrogen oxide
    E. Ozone
    (a) Only C
    (b) A, B and E
    (c) C and D
    (d) A, D and E
    
    Correct option: (c) C and D
    Solution: Oxides of sulphur and nitrogen dissolve in rain water and form acids.
    
    Case Study Questions
    
    
13. We find that a combustible substance cannot catch fire or burn as long as its temperature is lower than its ignition temperature. Have you ever seen cooking oil catching fire when a frying pan is kept for a long on a burning stove? Kerosene oil and wood do not catch fire on their own at room temperature. But, if kerosene oil is heated a little, it will catch fire.
    (a) What is meant by ignition temperature?
    (b) How does a matchstick catch fire?
    (c) Priyanka noticed that sodium metal is kept immersed in kerosene the chemistry laboratory. Why is sodium metal kept immersed in kerosene?
    
    Solution:
    (a) The lowest temperature at which a substance catches fire is called its ignition temperature.
    (b) By rubbing a matchstick against a rough surface (friction), it attains its ignition temperature and thus catches fire.
    (c) Sodium has very low ignition temperature, i.e., it catches fire on coming in contact with air, so it is kept in kerosene.
    
    
14. Combustion of coal dust has resulted in many disastrous fires in coal mines. Spontaneous forest fires are sometimes due to the heat of the sun or due to lightning strike. However, most forest fires are due to the carelessness of human beings.
    We generally have fireworks on festival days. When a cracker is ignited, a sudden reaction takes place with the evolution of heat, light and sound. Bring a burning matchstick or a gas lighter near a gas stove in the kitchen. Turn on the knob of the gas stove. We find that the gas burns rapidly and produces heat and light.
    (a) What is meant by rapid combustion? Which of the mentioned examples demonstrates this?
    (b) What is meant by explosion? Which of the mentioned examples demonstrates this?
    (c) What is meant by spontaneous combustion? Which of the mentioned examples demonstrates this?
    
    Solution:
    (a) Fuel burns quickly producing heat and light is known as rapid combustion. Example which demonstrates rapid combustion is burning of matchstick.
    (b) Fuel burns with sudden reaction evolving of heat, light and sound is known as explosion. Example which demonstrates explosion is when a cracker is ignited, a sudden reaction takes place with the evolution of heat, light and sound.
    (c) Fuel burns at room temperature on its own is known as spontaneous combustion.
    Examples which demonstrates spontaneous combustion are combustion of coal dust has resulted in many disastrous fires in coal mines. Spontaneous forest fires are sometimes due to the heat of the sun or due to lightning strike or due to carelessness of human being
    
    
15. The increasing fuel consumption has harmful effects on the environment. Global warming is the rise in temperature of the atmosphere of the earth. This results, among other things, in the melting of polar glaciers, which leads to a rise in the sea level, causing floods in the coastal areas. Low lying coastal areas may even be permanently submerged under water.
    
    (a) What is meant by global warming? Mention cause for the same.
    (b) Give consequences of global warming.
    (c) Explain acid rain and its consequences.
    
    Solution:
    (a) Global warming is the rise in temperature of the atmosphere of the earth.  Combustion of most fuels releases carbon dioxide in the environment. Increased concentration of carbon dioxide in the air is believed to cause global warming.
    (b) Consequence of global warming:
    Global warming results into the melting of polar glaciers which leads to a rise in the sea level, causing floods in the coastal areas. Low lying coastal areas may even be permanently submerged under water
    (c) Burning of coal and diesel releases sulphur dioxide gas. It is an extremely suffocating and corrosive gas. Moreover, petrol engines give off gaseous oxides of nitrogen. Oxides of sulphur and nitrogen dissolve in rain water and form acids. Such rain is called acid rain. It is very harmful for crops, buildings and soil.
    
    Subjective Questions
    
    
16. Prathamesh lit a candle and placed a glass over it. He noticed that the candle eventually went out of flame. What could be the cause of this?
    
    
    Solution:
    The existence of fuel and oxygen are required for combustion to occur. The oxygen supply is cut off when the burning candle is covered with glass. As a result, the candle will eventually stop burning once the oxygen in the closed glass has been totally exhausted for burning.
    
    
17. Kiran and his mother went to a goldsmith to get jewellery made from a 24 carat gold coin that his mother had purchased on the occasion of Akshay Tritiya. He noticed the goldsmith blowing in the flame to melt the gold. Which flame zone would a goldsmith employ to melt gold or silver, and why?
    
    
    Solution:
    The outermost non-luminous blue coloured zone of the flame has a high temperature as this part of the flame is the hottest part of the flame. Goldsmith blows in this zone to melt silver and gold.
    
    
18. What is meant by “Fuel”? Give examples for the same.
    
    Solution:
    The fuel is a source of heat and energy for domestic and industrial purposes.
    Example: wood, charcoal, petrol, kerosene, etc.
    
    
19. Mention the characteristics of an Ideal fuel.
    
    Solution:
    i. A good fuel is one which is readily available.
    ii. It is cheap.
    iii. It burns easily in air at a moderate rate.
    iv. It produces a large amount of heat.
    v. It does not leave behind any undesirable substances.
    
    Assertion Reasoning Questions
    
    Below questions consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:
    
20. Assertion (A): For fires involving electrical equipment and inflammable materials like petrol, carbon monoxide (CO) is the best extinguisher.
    Reason (R): CO₂, being heavier than oxygen, covers the fire like a blanket.
    
    Correct option: (d) A is false but R is true.
    Solution: For fires involving electrical equipment and inflammable material like petrol, carbon dioxide is the best extinguisher. Carbon dioxide being heavier than oxygen covers the fire like a blanket. Since the contact between the fuel/inflammable material and oxygen is cut off, the fire is extinguished.
    
    
21. Assertion (A): The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value.
    Reason(R): Calorific value of Cow dung cake is 15000 kJ/kg.
    
    Correct option: (c) A is true but R is false.
    Solution: Calorific value of Cow dung cake is 6000 - 8000 kJ/kg
    
    
22. Assertion (A): Food is fuel for our body.
    Reason (R):  Food gives energy to your body to carry out different processes.
    
    Correct option: (a) Both A and R are true and R is the correct explanation of A 
    Solution: In our body, food is broken down by reaction with oxygen and heat is produced. Food gives energy to your body to carry out different processes.
    
    
23. Assertion (A): CNG is preferred as automobile fuel over diesel and petrol.
    Reason (R): CNG is a cleaner fuel.
    
    Correct option: (a)  Both A and R are true and R is the correct explanation of A
    Solution: The use of diesel and petrol as fuels in automobiles is being replaced by CNG (Compressed Natural Gas), because CNG produces the harmful products in very small amounts. CNG is a cleaner fuel
    
    
24. Assertion (A): Carbon fuels like wood, coal cause respiratory diseases, such as asthma.
    Reason (R): People can develop asthma after exposure to things such as pollen, animal fur or feather, etc.
    
    Correct option: (b)  Both A and R are true and R is not the correct explanation of A
    Solution: Carbon fuels like wood, coal, petroleum release unburnt carbon particles. These fine particles are dangerous pollutants causing respiratory diseases, such as asthma.