Combustion and Flame Chapter 4 Science Class 8 Extra Questions

i.Petrol and diesel.
ii.45,000 kilojoules per kilograms
iii.The excessive production of carbon dioxide gas causes the over-heating condition. This over-heating condition is called global warming.
iv.Liquid Petroleum Gas
v.The flame is a region where the combustion takes place.

(i)The fire extinguisher is a portable apparatus used to control the level of unwanted fire at a certain place. Two types of fire extinguishers are- carbon dioxide and soda-acid.
(ii)The efficiency of fuel that calculates the heat released when one gram of fuel burns completely in oxygen.
(iii)The fuels that are present in a limited amount are called non-renewable fuels. Coal and petroleum are two examples of non-renewable fuels.
(iv)The fuels that are found in the form of gaseous state are called gaseous fuels. Hydrogen and coal gas are two examples of gaseous fuels.
(v) The combustion that takes place slowly at a low temperature is called slow combustion. Digestion and rustling are two examples of slow combustion.

The colour of the flame is blue because the air hole of the burner opens which means it provides sufficient supply of oxygen.

Luminous zone is a middle zone or zone of incomplete combustion because it takes place in the presence of limited air.

Brief description about solid fuels, liquid fuels and gaseous fuels are given below: -

The three characteristics of an ideal fuel are as follows: -

• High calorific value.
• Moderate ignition temperature.
• Easy to store and transport.

If anyone inhales carbon monoxide, it mixes with his/her haemoglobin and produces carboxyhaemoglobin which decreases the amount of oxygen carrying by the blood and causes respiratory disorders, headache, dizziness and fatigue.

Carbon dioxide gas is responsible for increasing global warming because the excess amount of CO₂ traps the heat produced by the sunrays and prevents it from reflecting back that causes the over-heating condition. This over-heating condition is called global warming.

The smoke released by the vehicles contains lead compounds that are poisonous. Therefore, the excessive releasing of the smoke populated the environment and continuous inhalation can cause respiratory disorders including cancer.

The general equation of chemical reaction for complete combustion is: -

All three zones of candle flame are explained in details below: -

Soda-fire extinguisher has a metallic cylinder that contains a saturated solution of sodium bicarbonate. A glass bottle filled with a concentrated sulphuric acid attached to the cap of the metal cylinder. The connection between the sodium bicarbonate and sulphuric acid produces carbon dioxide when anyone struck the knob. Afterwards, carbon dioxide forms a blanket over the burning area that cut-off the interaction between the fire and air resulting the excavation of fire.