NCERT Solutions Class 8 Science Chapter 6 Combustion And Flame
NCERT Solutions Class 8 Science Chapter 6 Combustion And Flame: National Council of Educational Research and Training Class 8 Science Chapter 6 Solutions – Combustion And Flame. NCERT Solutions Class 8 Science Chapter 6 PDF Download.
NCERT Solutions Class 8 Science Chapter 6: Overview
|
Board |
NCERT |
|
Class |
8 |
| Subject |
Science |
|
Chapter |
6 |
| Chapter Name |
Combustion And Flame |
|
Topic |
Exercise Solutions |
NCERT Solutions Class 8 Science Chapter 6 – Combustion And Flame
CHAPTER: – 6
(COMBUSTION AND FLAME)
Exercise: –
1)List conditions under which combustion can take place.
Ans: -The condition for the combustion is
- There should be inflatable substance.
- Oxygen presence.
- Ignition temperature should be reached.
2) Fill in the blanks.
(a) Burning of wood and coal causes ___pollution______of air.
Explanation – (As in this burning various toxic gases are liberated)
(b) A liquid fuel, used in homes is__kerosene_______.
Explanation – (This is the main source in fuel and easily available in domestic uses)
(c) Fuel must be heated to its __ignition temperature______ it starts burning.
Explanation – (This temperature is different in different fuel which also known as ignition point)
(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.
Ans: – we generally use CNG instead of LPG because of the pollution of atmosphere. As the CNG is less polluted or doesn’t affect the environment much this uses increasingly and as a result pollution is reducing in our cities.
4)Compare LPG and wood as fuels.
Ans: –
| LPG |
WOOD |
| Ignition temperature less. | High ignition temperature. |
| There is no resides. | Ashes remain after burning. |
| Transportation easily. | Transportation comparably difficult. |
5) Give reasons.
(a) Water is not used to control fires involving electrical equipment.
Ans: – The water should not apply while there is fire broke out because of the electricity. As this water would made theshot circuit. So, when water will be applied all the electronic equipment get current through water and for this we must avoid and should choose alternative way.
(b) LPG is a better domestic fuel than wood.
Ans: – As LPG transfer easily to our home as compared to the wood or other fuel. We can Carry LPG through the container ship for transfer from one continent to other as well. The wood also liberates toxic as in area although.
(c) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.
Ans: –A paper is dry in nature and easily capture the fire. But the metal like aluminium doesn’t allow the fire so, if we wrapped this paper with this aluminium this will not catch fire easily.
6) Make a labelled diagram of a candle flame.
Ans: –
7)Name the unit in which the calorific value of a fuel is expressed.
Ans: – In kilojoule per kilograms or Kj/kg expressed the calorific value of fuel.
8)Explain how CO2 is able to control fires.
Ans: – The fire broke out in a area where the availability of oxygen. And we also known that the oxygen is less heavy than the CO2 as a result of that this carbon dioxide create a blanket like cover around the fire and then fire came in control.
9)It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain.
Ans: – In green leaves their present water in it so when we try to burn this leaves the ignition temperature of this could not get. And as in dry leaves there’s no water present in that it catches fire easily.
10)Which zone of a flame does a goldsmith use for melting gold and silver and why?
Ans: – As we all know the outermost region of a flame is hottest region. So, in case of Goldsmith the outer most is used for the melting of silver and gold.
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.
Ans: – As we know, Heat produced= calorific value × weight of the fuel;
Here, calorific value=?
Heat produced= 180000KJ.
Weight=4.5 Kg,
Calorific value= 180000/ 4.5 = 40,000 KJ / Kg.
12)Can the process of rusting be called combustion? Discuss.
Ans: – As we all know that the combustion always happens in the presence of the air. In rusting the upper surface of the iron with the reaction of oxygen present in air form it. So, both of this reaction is similar in nature.
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?
Ans: – As we all know the outer part of the flame always more powerful or hottest as compared to the inner part. So, when Ramesh kept the beaker in the outermost flame then this water of the beaker will heat more as compared to Abida beaker which kept in the yellow region of the flame.
