Chemical Equations

Chemical Equations

Author: carolyn fruin

This lesson will show how chemical reactions are written and how to use the Law of Conservation of Matter to balance chemical equations.

Learning Targets

  • I know how to represent reactants, products, physical states and direction in a chemical equation.
  • I can identify and write balanced chemical equations and determine the number of atoms in the reactants and products.
  • I know how the conservation of matter plays a role in chemical equations.
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Strategy for Balancing Equations

  1. Figure out which elements to balance First, Middle, and Last. Always start by deciding which elements to save for last:
  • Last: any element that appears by itself (anywhere in the equation)
  • First: elements that appear in only one molecule on each side (if you haven’t already saved them for last).
  • Middle: every element that’s not already last or first.
  1. Start with any element on the “First” list.  Add coëfficients to make it balance.
  2. Pick another element.  (Work your way through the “First,” then “Middle,” then “Last” lists.) Start with elements that already have at least one coëfficient, but still need at least one.
  3. Repeat step #3 until everything is balanced.


  • Polyatomic ions usually stay together

Source: Mr. Bigler

Chemical Equations - Intro and Balancing

Balancing Chemical Equations 1

Quick example of balancing a chemical equation.

KhanAcademy - Balancing Chemical Equations

Source: KhanAcademy