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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 water H2 + O2 → H2 O Nitrogen plus hydrogen yields ammonia N2 + 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: Decomposition
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 CB A 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.

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