Chemical reactions are occurring around us all the time

–Food cooking –Fuel being burned in a car’s engine –Oxygen being used in the human body

To describe the reaction that creates fire at the bunsen burner in lab:

Methane gas reacts quickly with oxygen gas to produce fire, carbon dioxide, and water vapor

That’s a lot to write!

We can simplify the description of our reaction by using a word equation:

Methane gas + oxygen gas →fire + carbon dioxide gas + water vapor

Still a lot to write!

The simpler way to express a chemical reaction is to use formula equations:

CH4 + O2 → CO2 + H2O

However there is some information that is not shown in the formula equation:

– State of matter – Fire/ Energy

We can show state of matter using the following symbols:

(s) solid(l) liquid(g) gas(aq) aqueous solution

(substance is dissolved in water)

CH4 (g)+ O2 (g) → CO2 (g) + H2O (g) + energy

Is the equation balanced?

CH4 (g)+ O2 (g) → CO2 (g) + H2O (g) + energy

CH4 (g)+ 2O2 (g) → CO2 (g) + 2H2O(g) + energy

Practice writing these equations:

Hydrogen plus oxygen yields waterH2 + O2 → H2 O

Nitrogen plus hydrogen yields ammoniaN2 + H2 → NH3

Aluminum bromide plus chlorine yields aluminum chloride and bromine

AlBr3 + Cl2 → AlCl3 + Br2

Balance and include state of matter:

2H2 (g) + O2(g) → 2H2 O(l)

N2 (g) + 3H2(g) → 2NH3(g)

2AlBr3(s) + 3Cl2(g) → 2AlCl3(s) + 3 Br2(l)

Nitrogen plus oxygen gas react and form dinitrogen pentoxide

2N2(g) + 5O2 (g) → 2N2 O5 (g)

There are five general types of reactions: Synthesis Decomposition Single-replacement Double-replacement Combustion

Decomposition Reaction

A reaction where a compound breaks down into two or more simpler products

Single Replacement Reaction

A single-replacement reaction is one in which one element replaces a second element in a

compound

Double Replacement Reaction

AB + CD = AD + CBA double-replacement reaction is a reaction

involving an exchange of positive ions between two compounds

Combustion Reaction

CH4 + 2O2 → CO2 + 2H2O + energy

• A combustion reaction is a reaction in which an element or a compound reacts with oxygen, to form an oxide and heat

• Hydrocarbons combust with oxygen to form carbon dioxide and water.