VIII(8th) Combustion and flame MCQ

Combustion and flame class 8th  MCQ (Multiple Choice Questions)
1.      Name the compound present in the head of match stick.
a) Antimony disulphide b) Potassium chlorate and antimony trisulphide
c) White phosphorous and potassium chlorate
d) Red phosphorous and potassium chlorate
2.      Which one does not burn with a flame?
a) Candle            b) Coal                        c) Kerosene oil            d) Molten wax
3.      A chemical process in which a substance reacts with oxygen to give off heat is_______.
a) Photosynthesis           b) Respiration              c) Combustion             d) Transpiration
4.      In the Sun, heat and light are produced by___________________.
a) Combustion    b) Explosion    c) Nuclear reaction      d) Conduction
5.      Magnesium burns in air to produce_________.
a) Mg(OH)2      b) MgO      c) MgO2       d) MgCO3
6.      Inflammable substances have:
a) high ignition temperature       b) low ignition temperature     c) no ignition temperature     d) high boiling point.
7.      Choose the best fire extinguisher.
a) Oxygen          b) Water          c) Carbon dioxide       d) Blanket
8.      The hottest part of a candle flame:
a) luminous zone            b) dark zone    c) hot zone      d) non-luminous zone.
9.      The colour of middle zone of the candle flame is:
a) Orange           b) Black           c) Yellow        d) Blue
10.  Complete combustion of wax vapours takes place in____________.
a) middle zone   b) luminous zone         c) non-luminous zone              d) dark zone
11.  The calorific value of wood when compared to LPG is:
a) less     b) more            c) same            d) no colorific value
12.  The unit of calorific value is:
a) kJ/kg               b) kg/kJ           c) kB/kJ           d) g/kJ
13.  Global warming is a result of:
a) increased O2   b) increased CO2         c) increased water vapour       d) increased CO
14.  A very poisonous gas:
a) Carbon dioxide          b) Nitrogen      c) Carbon monoxide   d) Oxygen
15.  A cleaner fuel for automobiles:
a) Petrol              b) Diesel          c) CNG           d) LPG
16.  This can not be used for fires involving electrical equipments:
a) Carbon dioxide       b) Oxygen       c) Water d) Fire extinguisher
17.        A liquid fuel used in homes:
a) water              b) LPG                        c) CNG           d) cooking oil
18.  Carbon monoxide is produced by:
a) incomplete combustion of fuels         b) explosion of fuels
c) complete combustion of fuels            d) sleeping in a closed room
19.  Sources of heat energy for domestic and industrial purposes are:
a) Matchstick     b) fuel              c) petrol           d) heater
20.  For melting gold and silver, a gold smith uses:
a) inner most zone of a flame     b) the least hot region
c) non-luminous zone               d) dark zone
21.  The zone of partial combustion is___________.
a) luminous zone            b) innermost zone        c) dark zone    d) non-luminous zone
22.  Use of Diesel and Petrol as fuel in automobiles is being replaced by:
a) LPG   b) CNG           c) Coal             d) Bitumen
23.  When an electrical equipment is on fire, the best extinguisher to be used is:
a) water              b) sunlight       c) CO2             d) O2
24.  What is the telephone number of fire service in Saudi Arabia?
a) 997                 b) 998              c) 999              d) 993
25.  When compared to wood the ignition temperature of kerosene oil is:
a) higher             b) lower           c) the same      d) no ignition temperature
1.  b 2.  b 3.              c 4.  c 5.  b 6.  b 7.  c 8.  d 9.  c 10.    c 11.    b	12.     a 13.    b 14.    c 15.    c 16.    c 17.    b 18.    a 19.    c 20.    c 21.    a 22.    b 23.    c 24.    b 25.    b

VIII(8th) Combustion and flame MCQ

CBSE 8th Solved Question Ch: Combustion and Flame Extra Mark Gainer

CHAPTER - 6 COMBUSTION AND FLAME CBSE Notes for class 8th

Class 8th solved question Combustion and Flame

CHEMISTRY-8th Combustion and Flame Assignment /Worksheet

CHAPTER - 6 COMBUSTION AND FLAME Ncert Notes for class 8th

CBSE 8th Solved Question Ch: Combustion and Flame Extra Mark Gainer

Class 8th solved question Combustion and Flame

1. Chose the substances which will produce flame on burning and why?  Charcoal, molten wax, paper, coal, mustard oil.

Ans: molten wax and mustard oil.

2. Draw a well labeled diagram for the flame of a candle and answer the following

Questions:

(a) Which zone is luminous and why ?

(b) Why is the innermost zone grey in colour and the coldest zone ?

(c) Which zone is called the zone of complete combustion and why?

Ans: (a) inner most zone is luminous due to partial combution . The unburnt carbon particles impart a pale yellow colour to the flame.

(b) The innermost zone is grey in colour and the coldest zone because It contains unburnt gas particles. No combustion takes place here as no oxygen is available.

(c)Outer most zone is called the zone of complete combustion Here, carbon and hydrogen are completely oxidized to Carbon dioxide and water vapour.

3. Calorific value of wood is approx.17000-22000kj/kg .what does it mean?

Ans: when 1 kg  fue (wood)  is burnt completely in oxygen produce approx.17000-22000kj heat energy.

4. Why is it dangerous to burn coal in a closed room?

An: When coal burn  in a closed room produce toxic fumes or smoke or other harmful product .

5. Write any four characteristics of good fuel .

Ans: he main characteristics of a good fuel are :-

i) Is readily available and cheap. ii) Does not leave behind any undesirable substances.

iii) Is easy to store and transport.  iv) Burns at a moderate rate.

v) Produces a large amount of heat.    vi)  Does not cause pollution.

6. Name the gases which lead to formation of acid rain?

Ans: 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.

7. In an experiment 10 Kg of a fuel produced 200,000 KJ 0f heat . Calculate the calorific value of the fuel

Ans: The calorific value of a fuel :- is the amount of heat energy produced on complete combustion of 1 kg of a fuel. The calorific valve of a fuel is expressed in kilo joule per kg.

The calorific value of the fuel = 200,000 KJ/10 Kg =200,00 KJ/kg

8. How does CO2 help in fire fighting?

Ans: Carbon dioxide is the best fire extinguisher to put out fire caused by inflammable materials like oil and petrol and electrical equipments. Carbon dioxide is heavier than air and it covers the fire and cuts off the supply of oxygen and puts out the fire.

9. What are the drawbacks of using solid fuel?

Ans: The drawbacks of solid fuels are as follows:

1. They have a high ignition temperature.

2. They produce a large amount of residue (soot, ash) after combustion.

3. Their calorific value is low.

10. What are the harmful effects on the environment due to burning of fuels?

Ans: i) Fuels like wood, coal, petroleum release unburnt carbon particles which cause respiratory diseases like asthma.

ii) Incomplete combustion of fuels release carbon monoxide gas which is a very poisonous gas which can cause death.

iii) Burning of most fuels release carbon dioxide gas which causes rise in the temperature of the atmosphere. This is called global warming. It causes melting of polar ice, rise in sea level and flooding of coastal areas.

CHAPTER - 6 COMBUSTION AND FLAME CBSE Notes for class 8th

Class 8th solved Question Combustion and Flame by Jsunil Tutorial

Class 8th solved question Combustion and Flame

1. Define Fuel. Give examples of solid, liquid and gaseous fuels.

Ans: The substance that undergoes combustion is called fuel. Fuels are substances which, on combustion produce heat energy without producing undesirable by-products.

Fuels are of three main types. They are :-

i) Solid fuels :- Eg:- wood, coal, charcoal etc.

ii) Liquid fuels :- Eg:- kerosene, petrol, diesel etc.

iii) Gaseous fuels :- Eg:- CNG, LPG, biogas, hydrogen etc.

2. Differentiate between combustible and non-combustible substances with two examples of each kind?

Ans: Combustible substances:- Substances which burn in air to produce heat and light are called combustible substances.  Eg :- wood, coal, charcoal, kerosene, petrol, diesel, liquified petroleum gas (LPG), compressed natural gas (CNG) etc.

Substances like stone, glass, iron nails, etc. do not burn on being exposed to flame. Such substances are called non-combustible substances.

3. What is combustion?

Ans:  Combustion: - The chemical process in which a substance reacts with oxygen to produce heat is called combustion.  Combustion is the burning of substances in air or oxygen to release heat and light.

e.g. magnesium burns to form magnesium oxide and produces heat and light.

4. Why does a candle stop burning when covered with a glass tumbler?

Ans: A candle stop burning when covered with a glass tumbler due to absence of oxygen that support burning. Air is necessary for combustion.

5. How is spontaneous combustion different from explosion?

Ans: Spontaneous combustion:- is combustion in which a substance burns spontaneously and produces heat and light without the help of external heat. Eg:- phosphorus burns spontaneously at room temperature

Explosion:- is a combustion in which a substance burns suddenly and produces heat, light and sound with the help of heat or pressure. Eg:- explosion of crackers on applying heat or pressure.

6. Special care should be taken to store kerosene oil. Give reason.

Ans: kerosene oil is combustible substance and produce heat and light immediately so Special care should be taken to store kerosene oil.

7. When the clothes of a person catch fire, the person is covered with a blanket to extinguish the fire. Can you guess why?

Ans: Blanket cut off supply of air or oxygen to extinguish the fire

8. Why is L.P.G labeled as inflammable substance?

Ans:  L.P.G has low ignition temperature and catches fire easily so L.P.G labeled as inflammable substance.

9. Which substance added to LPG to detect any leakage?

Ans: A small amount of ethyl mercaptan, an inert gas with a characteristic odour, is added to LPG to detect any leak.

10. How does water help to extinguish fire?

Ans:  When water is poured over a burning substance, it absorbs heat from the substance. As a result the temperature of the substance falls below the ignition temperature, and it stops burning

CHAPTER - 6 COMBUSTION AND FLAME CBSE Notes for class 8th