Meaning of fuels,heating value,causes of fuel pollution and factors to consider when choosing a fuel.
Answer Text: Fuels:- Are compounds which produce a high heat of combustion.- Fuels can be:-- Solids; such as charcoal, wood, coal.- Liquids; such as ethanol, gasoline- Gaseous; such as methane, water, gas etc.Basic concepts:- Calorific value- Is the energy content of a fuel;- Is the heat evolved when a given mass of fuel is completely burnt in oxygen;Note:- Sometimes fuels may undergo incomplete combustion.- Incomplete combustion of fuel is disadvantageous inthat:-- It reduces the energy content.- It leads to pollution.- Heating value:- Is the amount of heat energy given out when a unit mass or unit volume of a fuel is completely burnt in oxygen.Fuel pollution.- Is commonly caused by internal combustion engine.- Fuel in engine (e.g. petrol) burns completely to water and carbon (IV) oxide, only under ideal conditions.Causes of fuel pollution:(i). Incomplete combustion which causes production of (produces) CO and unburnt carbon (soot).(ii). Some fuels contain sulphur and nitrogen and on combustion release #SO_2# and #NO_2#. These gases are acidic, resulting to acidic rain whichcorrodes buildings and affects trees and animals in various ways.(iii). Fuel additives; e.g. tetraethyl lead, Pb (#C_2H_5)_4# added to petrol to enhance burning efficiency produces volatile lead compounds in the exhaust fumes.- Lead is very poisonous and affects the nervous system and the brain in children.Factors to consider when choosing a fuel.(i) Heating value,(ii) Ease and rate of combustion.(iii) Availability(iv) Ease of transportation(v) Ease of storage(vi) Environment effects.