Fill in the blanks.
a) Fuels release their energy through a chemical reaction known as_______.
b)_________reaction is accompanied by the evolution of heat.
c) The substances which_____
easily on burning give flames.
d) Changing of solids directly into vapour on heating is called________.
e) Unburnt carbon particles form________which appears as a dark powder.
f)________should never be used in case of an electrical fire.
Answers
Answer:
EXOTHERMIC reaction.
Explanation:
1) Hydrocarbon fuels like methane (CH4) burn in the presence of oxygen to produce carbon dioxide and water. This process of combustion releases energy. When energy is released during the course of a chemical reaction, it is said to be an EXOTHERMIC reaction.
2)Energy is absorbed to break bonds, and energy is evolved as bonds are made. ... Such a reaction is said to be endothermic if the energy is in the form of heat. The opposite of endothermic is exothermic; in an exothermic reaction, energy as heat is evolved.
3)The substances which have very low ignition temperature and can easily catch fire with a flame are called inflammable substances. Examples of inflammable substances are petrol, alcohol, Liquified Petroleum Gas (LPG) etc.
4)Vaporization, conversion of a substance from the liquid or solid phase into the gaseous (vapour) phase. ... Direct conversion from solid to vapour is called sublimation.
5)Unburnt carbon particles form "ash" which appears as dark powder. The answer is "Ash".
6)You should never throw water on an electrical fire because water conducts electricity and you could be electrocuted. ... If you don't have a fire extinguisher, you can use baking soda to extinguish an electrical fire