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Olympiad Test: Combustion & Flame


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20 Questions MCQ Test Science Class 8 | Olympiad Test: Combustion & Flame

Olympiad Test: Combustion & Flame for Class 8 2023 is part of Science Class 8 preparation. The Olympiad Test: Combustion & Flame questions and answers have been prepared according to the Class 8 exam syllabus.The Olympiad Test: Combustion & Flame MCQs are made for Class 8 2023 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Olympiad Test: Combustion & Flame below.
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Olympiad Test: Combustion & Flame - Question 1

What are the two main hydrocarbons present in L.P.G.?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 1

L.P.G. is a mixture of hydrocarbons. It consists of butane, propane and ethane but butane and propane are the two major constituents of L.P.G.

Olympiad Test: Combustion & Flame - Question 2

What is the heat produced by burning 1 g of fuel completely known as?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 2

Calorific value of a substance is the amount of heat released during the combustion of a specified amount of fuel or food. The calorific value is the characteristic of a substance.

Olympiad Test: Combustion & Flame - Question 3

Which of the following has the highest calorific value?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 3

Natural gas has the highest calorific value of 50000 kJ/kg Petrol has 45000 kJ/kg Kerosene has 45000 kJ/kg and Coke has 28000 kJ/kg

Olympiad Test: Combustion & Flame - Question 4

Which of the following has the characteristics of a good fuel?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 4

All the given substances can act as fuels but butane is considered as a good fuel because of the following characteristics:
(i) Exists in gaseous state
(ii) Has high calorific value
(iii) Does not form poisonous products during combustion

Olympiad Test: Combustion & Flame - Question 5

What is burning of a substance in the presence of air with the evolution of heat called?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 5

The process of a substance burning in the presence of air with evolution of heat is called combustion.

Olympiad Test: Combustion & Flame - Question 6

When methane burns in air, what are the products formed?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 6

Fuels and hydrocarbons burn in oxygen and form 

CO2+2O2→CO2+2H2O+heat

and give out heat. 

CH4+2O2→CO2+2H2O+heat

Olympiad Test: Combustion & Flame - Question 7

What kind of reaction is combustion?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 7

Combustion is an oxidation reaction accompanied by heat and light.

Olympiad Test: Combustion & Flame - Question 8

Which of the following is a non- combustible substance?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 8

Diamond is a non-combustible substance.

Olympiad Test: Combustion & Flame - Question 9

What is the lowest temperature at which a substance starts burning called?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 9

The temperature at which a substance starts burning on heating is called ignition temperature. Highly    inflammable substances have a low ignition temperature. Hence, they catch fire easily.

Olympiad Test: Combustion & Flame - Question 10

If the temperature falls below its ignition temperature, then what happens to the burning substance?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 10

A burning substance will be extinguished if the temperature falls below its ignition temperature.

Olympiad Test: Combustion & Flame - Question 11

Which of the following is an example of rapid combustion?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 11

Rapid combustion is a form of combustion in which large amounts of heat and light energy are released. Candle shows rapid combustion, whereas cracker and white Phosphorous come under explosion and spontaneous combustion respectively.

Olympiad Test: Combustion & Flame - Question 12

In which of the following types of combustion are heat, light and sound produced?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 12

The combustion in which heat, light and sound are produced is known as explosive combustion.

Olympiad Test: Combustion & Flame - Question 13

I Match the entries in Column-l with those in Column-ll correctly.

Detailed Solution for Olympiad Test: Combustion & Flame - Question 13

The correct combination is a - 3, b - 4, c - 2, d - 1
(i) Dark inner zone -Unburnt vapours of wax
(ii) Blue zone - Complete combustion
(iii) Luminous zone ? Partial combustion
(iv) Non-luminous zone - Hottest part (no carbon)

Olympiad Test: Combustion & Flame - Question 14

What does the blue zone in an L.P.G. flame indicate?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 14

The blue zone in L.P.G. flame indicates the hottest zone where complete combustion takes place.

Olympiad Test: Combustion & Flame - Question 15

What does natural gas contain?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 15

Natural gas consists of methane, ethane, propane etc., of which methane forms major composition of about 95%.

Olympiad Test: Combustion & Flame - Question 16

How is synthetic petrol produced?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 16

The Bergius Process is a very simple process for converting brown coal completely into crude oil. It was invented by Dr. Friedrich Bergius. In this process, brown coal, also known as lignite is powdered and mixed with heavy oil and heated with hydrogen under high pressure of about 200-250 atm. and a temperature of about 748 K in the presence of iron oxide as catalyst. The vapours on condensation give a liquid resembling crude oil. This is called synthetic petrol, which on fractional distillation gives petrol (gasoline).

Olympiad Test: Combustion & Flame - Question 17

Arrange the following fuels in the increasing order of their calorific value.

(i) Petrol
(ii) Wood
(iii) Coal
(iv) Natural gas

Detailed Solution for Olympiad Test: Combustion & Flame - Question 17

Wood - 17000 to 22000 kJ/kg
Coal - 25000 to 33000 kJ/kg
Petrol - 45000 kJ/kg
Natural gas - 50000 kJ/kg
The correct order of the increasing order of calorific values is: (ii), (iii), (i), (iv).

Olympiad Test: Combustion & Flame - Question 18

What does the incomplete combustion of a fuel give?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 18

When a fuel (carbon) undergoes incomplete combustion, carbon monoxide is formed. It is a poisonous gas and fatal, if inhaled.

Olympiad Test: Combustion & Flame - Question 19

The total amount of heat produced by a fuel having a calorific value of 20 kJ kg 1 was found to be 50,000 joules. How much fuel was burnt?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 19

1 kg of fuel when burnt gives 20,000 joules of heat energy. 50,000 joules of heat energy will be produced by 2.5 kg of fuel as given below. 1 kg fuel produces 20kJkg−1 heat ? fuel produces 50kJkg−1 heat 

Olympiad Test: Combustion & Flame - Question 20

What is combustion?

Detailed Solution for Olympiad Test: Combustion & Flame - Question 20

Combustion is burning of a substance in the presence of oxygen. During this process heat energy is released, it is therefore an oxidation and exothermic reaction.

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