Read and download free pdf of CBSE Class 8 Science Combustion And Flame Worksheet Set A. Students and teachers of Class 8 Science can get free printable Worksheets for Class 8 Science in PDF format prepared as per the latest syllabus and examination pattern in your schools. Standard 8 students should practice questions and answers given here for Science in Grade 8 which will help them to improve your knowledge of all important chapters and its topics. Students should also download free pdf of Class 8 Science Worksheets prepared by school teachers as per the latest NCERT, CBSE, KVS books and syllabus issued this academic year and solve important problems with solutions on daily basis to get more score in school exams and tests
Worksheet for Class 8 Science Chapter 6 Combustion and Flame
Class 8 Science students should refer to the following printable worksheet in Pdf for Chapter 6 Combustion and Flame in standard 8. This test paper with questions and answers for Grade 8 Science will be very useful for exams and help you to score good marks
Class 8 Science Worksheet for Chapter 6 Combustion and Flame
CBSE Class 8 Science Worksheet - Combustion and Flame Part A. Revision worksheets, Sample papers, Question banks and easy to learn study notes for all classes and subjects based on CBSE and CCE guidelines. Students and parents can download free a collection of all study material issued by various best schools in India. The study material has been carefully compiled by the best teachers in India. The students should practice the questions database to get better marks in examination. Please refer to other links for free download of high quality study material. Based on CBSE and CCE guidelines. Based on the same pattern as released by CBSE every year. Study material for final/ term/ SA1/ SA2 Examinations conducted by various schools affiliated to Central Board of Secondary Education (CBSE) in India and abroad. CBSE Study material has been compiled to help students preparation which will helps the students to concentrate more in areas which carry more marks.
COMBUSTION AND FLAME
Question 1. List conditions under which combustion can take place.
Answer- There are certain conditions required for combustion to take place. They are:
(i) Presence of a fuel,
(ii) Air (or oxygen),
(iii) Temperature greater than ignition temperature.
Question 2. Fill in the blanks.
(a) Burning of wood and coal causes Pollution of air.
(b) A liquid fuel, used in homes is Kerosene.
(c) Fuel must be heated to its Ignition Temperature before it starts burning.
(d) Fire produced by oil cannot be controlled by Water.
Question 3. Explain how the use of CNG in automobiles has reduced pollution in our cities.
Answer- As the amount of unburnt carbon particles produced is very less in comparison to petrol and amount of harmful gases produced is also very less ,so CNG is comparatively a cleaner fuel than petrol.
Question 4. Compare LPG and wood as fuels
Answer-
LPG Wood
1. Leaves no residue after burning. 1. Leaves a lot of ash on burning.
2. It can be easily stored and transported. 2. It cannot be easily stored or transported.
3. It burns easily. 3. It burns comparatively with difficulty.
4. It has low ignition temperature. 4. It has high ignition temperature.
5. It is almost pollution free. 5. It causes a lot of pollution.
Question 5. Give reasons.
(a) Water is not used to control fires involving electrical equipment.
Answer- Because water is a good conductor of electricity, so it may result in electric shock to the user while controlling fire involving electrical equipments with water.
(b) LPG is a better domestic fuel than wood.
Answer- Because LPG neither produces pollution nor leave residue, on burning as compared to wood. LPG has much higher calorific value than wood.
(c) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.
Answer- This is because aluminium, being a metal, is a good conductor of heat. Therefore, heat is transferred from the paper to the metal and the paper does not attain its ignition temperature.
Question 6- Make a labelled diagram of a candle flame.
Answer-
Question 7. Name the unit in which the calorific value of a fuel is expressed.
Answer- Calorific value is defined as the energy contained in the fuel. It is expressed in the form kilojoule per kilogram (kJ/kg).
Question 8. Explain how CO2 is able to control fires.
Answer- CO2 being heavier than oxygen, covers the fire like blanket and also brings down the temperature of fuel. Since the contact between the fuel and oxygen is cut off, the fire comes under control.
Question 9. It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain.
Answer- Green leaves have a lot of moisture in them. This moisture does not allow them to catch fire easily.However, dry leaves have no moisture in them. Therefore, they catch fire easily.
Question 10. Which zone of a flame does a goldsmith use for melting gold and silver and why?
Answer- Goldsmiths use the outermost part/zone of the flame to melt gold and silver. This is because the outermost zone of the flame undergoes complete combustion and is the hottest part of the flame.
Question 11. In an experiment 4.5 kg of a fuel was completely burnt. The heat produced was measured to be 180,000 kJ. Calculate the calorific value of the fuel.
Answer- Calorific value of fuel is =180000kJ/4.5kg. = 40,000 kJ/kg.
Question 12. Can the process of rusting be called combustion? Discuss.
Answer- Combustion is a chemical process in which a substance reacts with oxygen and gives out energy during the process in the form of either heat or light or both. Rusting of iron is an exothermic process as heat is released during rusting. Hence, it is a kind of slow combustion.
Question 13. Abida and Ramesh were doing an experiment in which water was to be heated in a beaker. Abida kept the beaker near the wick in the yellow part of the candle flame. Ramesh kept the beaker in the outermost part of the flame. Whose water will get heated in a shorter time?
Answer- The water in the Ramesh's beaker will heat up in a shorter time. This is because the outermost zone of a flame is the hottest zone, while the yellow zone (in which Abida had kept the beaker) is less hot.
ONE MARK MCQs
1. If you hold a piece of iron wire with a pair of tongs inside pure oxygen in a candle flame or Bunsen burner flame. Name the colour of flame with which it will burn ?
a) Blue
b) Gold (✓)
c) Blue- Green
d) light purple
2. The ignition temperature of four substances P, Q, R and S are 125ºC, 270ºC, 150ºC and 310ºC respectively. Which of following pairs of substances catches fire at 250ºC?
a) Q & S
b) P & R (✓)
c) R & S
d) P & Q
3. Ankit was surprised after watching an experiment in science lab, His teacher put substance that catches fire spontaneously in presence of air, at room temperature. The name of that substance was
a) White phosphorous (✓)
b) sulphur
c) Calcium
d) Iron
4. Why is L.P.G, used as domestic fuel, mixed with a strong smelling volatile liquid like mercaptan?
a) For better combustion
b) For good smell
c) For detection of gas leakage (✓)
d)For high calorific value
5. The given table lists some of the fuel along with their calorific temperature
Fuel calorific value (KJ/g) Ignition temperature (0ºC)
P 100 5
Q 80 50
R 30 60
S 20 70
Which of the following fuel is an ideal fuel?
a) P
b) Q (✓)
c) R
d) S
6. Choose the correct option.
a) Air is not necessary for combustion.
b) Magnesium is a non-combustible metal.
c) CO2 is an excellent fire extinguisher. (✓)
d) Caloric value of wood is higher than that of Coal.
7. Match the following item of column A with the item of column B for the Flame of Candle.
8. Hydrogen gas has the highest calorific value i.e, 150 kJ /kg, yet it is not used as a fuel. Why?
a) it is explosive in nature (✓)
b) is limited in nature
c) it causes storage problem
d) it causes transportation problem
9. Juhi observes that kerosene oil and molten wax burn with flame but charcoal does not produce a flame. She concluded that it is due to
a) Charcoal is hard and kerosene and wax are soft
b) The substances which produces vapours during burning give flame (✓)
c) Both (a) and (b) are correct.
d) None of these
10. During birthday celebration, Raghav noticed that a candle flame always points upwards. The possible reason could be ?
a) Gases produced in a flame are cool, hence lighter. Therefore, they rise up.
b) Gases produced in a flame are hot, hence lighter. Therefore, they rise up. (✓)
c) Both (a) and (b) are correct.
d) None of these
11. Ram and Rahim were doing an experiment in which water was to be heated in a beaker. Ram kept beaker near the wick in the yellow part of the candle flame. Rahim kept the beaker in outermost part of the flame. Whose water will get hot in shorter time?
a) Ram‘s beaker will heat up in shorter time
b) Rahim‘s beaker will heat up in shorter time (✓)
c) Both (a) and (b)
d) None of these
12. Aman saw a fire in the wood and fire goes off when water is poured over burning wood. He asked his science teacher about the reason
a) It happens because water absorbs a large amount of heat and decreases the ignition temperature of wood and fire goes off. (✓)
b) Water cut the supply of oxygen which is necessary to catch fire.
c) Nothing to do with Ignition temperature
d) Both (a) and (b) are correct.
13. Ankita saw if kerosene oil is heated a little, it will catch fire But if wood is heated a little it would not catches fire . It is due to
a) Ignition temperature of kerosene oil is lower than that of wood (✓)
b) Ignition temperature of kerosene oil is more than that of wood
c) Kerosene react abruptly with oxygen
d) None of these
14. The Head of safety match stick contain red brown substances which is made of :
a) Antimony trisulphate
b) Potassium chloride
c) Both (a) and(b) (✓)
d)None of theses
15. A family consume 12kg of L.P.G.in 30 days. Calculate the average energy consumed per day, if the calorific value of L.P.G. is 50 kJ/kg.
a) 10000 J per day
b) 15000 J per day
c) 20000J per day (✓)
d) 25000 J per day
16. Amount of heat energy produced on ____combustion of 1kg of fuel is Calorific value.
a) Incomplete
b) Complete (✓)
c) Half
d) None of these
17. Inspite of the danger involved with hydrogen, it is used for some application. Where it is used?
a) Rocket fuel (✓)
b) Oxyhydrogen flame
c) Car fuel
d) All of above
18. In summer we feel very hot, It is because of global warming. Global Warming occurs due to _____concentration of CO2 in air.
a) Decreased
b) increased (✓)
c) Both (a) and (b)
d) None of these
19. In Agra, The Taj Mahal marbleis getting corroded due to acid rain. This rain is caused by Oxid of:
a) Sulphur, Nitrogen (✓)
b) Carbon, Nitrogen
c) Sulphur, Carbon
d) Phosphorous, Carbon
More Question-
Name the following
1. The materials which produce heat energy on burning in air.
2. Ignition temperature of Phosphorous.
3. Mixture on which side of match box is coated.
4. Materials which exhibit slow combustion.
5. Any two substances which burst into flames when kept in air for some time.
6. A region of burning gases.
7. The coldest part of candle flame.
8. A fuel with least calorific value.
9. A gas produced during combustion which causes acid rain.
10. Any three examples of inflammable substances.
11. Any three examples of gaseous fuels.
12. Any three examples of solid fuels.
13. Different zones of candle flame.
14. Process of production of energy in sun.
Tick the correct answer :
1. For the combustion reaction temperature of contribute material should be
(i) Lower than the ignition temperature.
(ii) Higher than the ignition temperature.
(iii) Equal to the ignition temperature.
(iv) None of the above.
2. Which one is an example of combustible substance.
(i) Natural gas
(ii) Glass pieces
(iii) Iron nails
(iv) None of the above.
3. Who were the people who introduced match sticks?
(i) Indians
(ii) Americans
Please refer to attached file for CBSE Class 8 Science Worksheet - Combustion and Flame Part A
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