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NCERT Solutions for Class 8 Science Chapter 6 : Combustion and Flame

Chapter 6 Combustion and Flame
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NCERT solutions class 8 Science Chapter 6 Combustion and Flame is one of the most crucial resources for class 8 students. This NCERT Solution will answer the questions on combustion, types of combustions, the role of oxygen in combustion, ignition temperature, inflammable substances, control of fire, different zones of flame and definition, pollutants that are dangerous, acid rain and its effects.

NCERT Solutions for Class 8 Science Chapter 6 by Swiflearn are by far the best and most reliable NCERT Solutions that you can find on the internet. These NCERT Solutions for Class 8 Science Chapter 6 are designed as per the CBSE Class 8 Science Syllabus. These NCERT Solutions will surely make your learning convenient & fun. Students can also Download FREE PDF of NCERT Solutions Class 8 Chapter 6.

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NCERT Solutions for Class 8 Science Chapter 6 : Combustion and Flame

1. List conditions under which combustion can take place.

Solution:
Conditions necessary for combustion are:
(a) Presence of a combustible substance.
(b) Presence of oxygen which is the supporter of combustion.
(c) Attainment of ignition temperature of the substance.

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 of air pollution.
(b) A liquid fuel, used in homes is LPG.
(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 plays an important role in reducing. The reasons are as follows:
CNG is a cleaner fuel.
CNG is an alternative for diesel, petrol and propane/LPG.
CNG contains few undesirable gases.

4. Compare LPG and wood as fuels.

Solution: Refer pdf.

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. This is the reason why water should not be used to control fires using electrical equipment.
(b) LPG neither produce gases, nor does it leave any residue behind. This is why LPG is better domestic fuel than wood. Moreover, it has more caloric value than wood.
(c) The ignition temperature of paper is low, that is why paper itself catches fire easily. But a piece of paper wrapped around an aluminium pipe does not catch fire easily, because the heat given gets absorbed by the aluminium pipe and the piece of paper does not get its ignition temperature

6. Make a labelled diagram of a candle flame.

Solution: Refer pdf.

7. Name the unit in which the calorific value of a fuel is expressed.

Solution:
The caloric value of a fuel can be expressed is kilojoules per kilogram (kJ/kg).

8. Explain how CO2 is able to control fires.

Solution:
CO2is heavier than oxygen. Therefore, it forms a blanket around fire. This in turn stops the supply of air. CO2also brings down the temperature of the burning substance. In these ways, it plays a significant role in controlling fires.

9. It is difficult to burn a heap of green leaves but dry leaves catch fire
easily. Explain.

Solution:
A heap of green leaves contains a lot of moisture in it, hence the ignition temperature is very high. Therefore it does not catch fire easily.
But dry leaves have no moisture content, hence its ignition temperature is low. Therefore 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, which is non-luminous 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:
Heat produced by 4.5 kg of fuel = 180,000 kJ
Caloric value of a fuel = heat produced by 1 kg of fuel
Therefore, calorific value of fuel == 40,000 kJ/kg

12. Can the process of rusting be called combustion? Discuss.

Solution:
No, because rusting is an exothermic process as heat is liberated during rusting. Combustion is a chemical process in which a substance reacts with oxygen to release energy in the form of heat or light. The process of rusting can be called slow combustion because iron emits heat during the formation of its oxide.

11. 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:
As Ramesh has put the water near the hottest part of the flame, his water will get heated in a shorter time.

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