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NCERT Solutions for Class 8 Science Chapter 4 Combustion and Flame will assist you in scoring more marks. This includes the textbook and their solutions for Combustion and Flame Chapter 4 of Class 8 Science, which is made in adherence to the updated syllabus 2023 released by CBSE.
Our solutions offer ample material to help students build a strong foundation and improve their understanding of the subject.
On this page, you will find all the NCERT Solutions for Class 8 Science Chapter 4 Combustion and Flame which includes detailed exercise-based solutions. These NCERT Solutions for Class 8 Science are downloadable and easy to access. Our Science experts have meticulously developed these solutions to support students in preparing for their Class 8 exams.
NCERT Solutions for Class 8 Science Chapter 4 Combustion and Flame
Combustion and Flame Class 8 Science NCERT Textbook Questions
Exercise Questions
1.List conditions under which combustion can take place.
Solution:
Conditions necessary for combustion are:
– Presence of a combustible substance
– Presence of air to sipply oxygen
– Proper ignition temperature
2. Fill in the blanks.
(a) Burning of wood and coal causes _______________ of air.
(b) A liquid fuel, used in homes is _________________.
(c) Fuel must be heated to its ____________________ before it starts burning.
(d) Fire produced by oil cannot be controlled by ____________________ .
Solution:
(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 .
3. Explain how the use of CNG in automobiles has reduced pollution in our cities.
Solution:
– CNG is comparitively a cleaner fuel
– Amount of unburnt carbon particles and harmful gases produced is less in CNG.
4. Compare LPG and wood as fuels.
Solution:
| LPG | Wood |
| (i) It is a liquid fuel | (i) It is a solid fuel |
| (ii) leaves no residue, no smoke | (ii) Leaves smokes and other harmful gases |
| (iii) Does not cause pollution | (iii) causes pollution |
| (iv) High Calorific Value ( 55 kJ/kg) | (iv) Low calorific value ( 17-20 kJ/kg) |
5. Give reasons.
(a) Water is not used to control fires involving electrical equipment.
(b) LPG is a better domestic fuel than wood.
(c) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.
Solution:
(a) Water is a good conductor of electricity, it may result in electric shocks to the person trying to extinguish fire. Also it can damage electrical equipments.
(b) LPG is better domestic fuel than wood because it does not produce gases, leaves no residue and it has more calorific value than wood.
(c) Paper by itself catches fire easily. But a piece of paper wrapped around an aluminium pipe does not catch fire easily because aluminium is a metal and is a good conductor of heat. The heat is transferred from the paper to the metal and the paper does not attain its ignition temperature.
6. Make a labelled diagram of a candle flame.
Solution:
7. Name the unit in which the calorific value of a fuel is expressed.
Solution:
Calorific value of a fuel is expressed in Kilojoules per kg (kJ/kg)
8. Explain how CO2 is able to control fires.
Solution:
CO2 is able to control fires because its heavier than oxygen and covers the fire like a blanket and cuts off the contact between oxygen and fuel. Also in cylinders, CO2 is kept in the liquid formand when its released, it expands enormously. This brings down the temperature of the fuel, which helps in controlling the fire.
9. It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain.
Solution:
Green leaves contain some moisture content which increases their gnition temperature and makes it difficult to burn easily. In case of dry leaves there is no moisture content which makes its ignition temperature less and it catches fire easily.
10. Which zone of a flame does a goldsmith use for melting gold and silver and why?
Solution:
A goldsmith uses the outermost zone of a flame to melt gold and silver as it is the hottest zone of the flame, having more temperature.
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.
Solution:
Calorific value of a fuel = Heat Produced / Amount of fuel
= 180,000 / 4.5
= 40,000 kJ/kg
12. Can the process of rusting be called combustion? Discuss.
Solution:
The process of rusting cannot be called combustion because in this process no heat and light is produced. Due to this reason iron is not considered as combustible substance.
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?
Solution:
Ramesh’s beaker will get heated in a shorter time because outermost zone of a flame is the hottest one, therefore that will get heated in shorter time.
Summary
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