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 SO2 and NO2. 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 (C2H5)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.