Chapter 10 - How can our energy resources be accessed fairly?

flash point

lowest temperature at which a substance gives off enough vapor to ignite when exposed to a flame or spark

ignition temperature

minimum temperature at which a substance will spontaneously ignite with out any external flame or spark

combustion definition

chemical reaction where a substance reacts rapidly with oxygen to produce heat and light

complete combustion

Occurs when a fuel burns in the presence of an abundant supply of oxygen. The fuel reacts fully with oxygen to produce co2 and h2o as the only products and releases a large amount of energy in the form of heat and light.

produces blue flame

CH4 + 2O2 → CO2 + 2H2O

incomplete combustion

occurs when there is not eough oxygen available for the fuel to burn completely. Carbon monoxide is produced as a by-product or a solid carbon.

produces yellow/red flame

2CH4 + 3O2 → 3CO + 4H2O

CH4 + O2 → C + 2H2O

enthalpy definition

sum of internal energy of a system and the product of its pressure and volume

average bond enthalpy

average amount of energy required to break one mole of a specific type of bond in a gaseous molecule. kJ/mol

standard enthalpy change of reaction

heat energy change that occurs during a chemical reaction when all reactants and products are in their standard states.

hess’ law

total enthalpy change of a reaction is the same no matter which route is taken provided the initial and final conditions are the same

hess law formula

sum of enthalpy of product - sum of enthalpy of reactants

what happens if chang ein enthalpy is negative and positive

exo and endo

calculation of enthalpy change

Q = mcT

entropy

measure of disorder or randomness in a system.

high → more disorder, more randomness, gas

low → more order, solids