Hands-On Math: Factoring and Balancing Chemical Equations

Written by Kim at The Learning Hypothesis.

Hands-on Chemical Equations Fun!

Chemistry requires a lot of algebraic thinking in order to be successful and it’s easy to incorporate hands-on chemical equations. Chemistry includes formulas, proportions, and the basis of the balanced chemical equation includes math concepts like the lowest common multiple, factoring, and the distributive property.

Balancing equations is necessary to satisfy the law of conservation of matter and simple means that what goes into a reaction comes back out.

The number of atoms on one side of the yields sign will equal the number on the other side.

Learning this kind of advanced math can be a bit tricky for students, so I like to make it as hands-on as I can.

This hands-on balancing chemical equations activity was a great way for my kids to visualize the concept as they learned.

How to Factor and Balance Chemical Equations

Let’s talk about the 3 mathematical concepts that are necessary to balance these equations:

• Lowest common multiple
• Factoring
• Distributive property

The lowest common multiple (LCM) is the smallest number that 2 (or more numbers) are factors of.

Factoring is the process of determining what combinations of numbers can be multiplied to create a specific product. It looks like this.

Distributive property says that multiplying a number by a group of numbers added together is the same as doing each multiplication separately.

In the case of balancing equations it means that when we add (or change) coefficients that the change will impact all of the elements in the formula.
Example

In this equation, there are 2 atoms of oxygen on the reactants side and 1 atom on the product side.
Reminder: the only thing that can be changed is the coefficient.

The LCM of 1 & 2 is 2. The factors of 2 are 1 & 2 so 2 is the first coefficient to try.

That 2 will multiply the 2 hydrogens and the 1 oxygen atom resulting in 4 hydrogen and 2 atoms.

Now the hydrogen are unbalanced. There are more hydrogen on the product side.

The LCM between the two sets of hydrogen is 4. The factors of 4 are 1 & 4 and 2 & 2.

To make the hydrogen on the reactants side equal the number on the products side we will use a coefficient of 2 on the reactant side. This results in 4 hydrogen atoms on both sides.

All balanced.

Now if all of that math, made your head spin. Let’s look at a hands-on way to work through balancing these chemical equations.

Hands-On Activity for Balancing Chemical Equations

Make Factor Trees:

Do a quick lesson/review on creating factor trees. This is something many students have done since upper elementary. This is a great review of factor trees.

I like to actually multiply the number of atoms to get a common multiple and use factor trees to determine the lowest common multiple and the coefficients needed for that number of atoms.

This is a quick example…

The factor trees make it easier to determine both the lowest common multiple and the coefficients (the factors of the LCM will be used in conjunction with the subscripts in the formulas

For instance if you were trying to balance an element with 4 atoms on the reactant side and 6 atoms on the product side, you can multiply those together to get 24.

Do a factor tree and quickly discover the lowest common multiple is 12 and the factors of 12 that will be used as coefficients.

Create a Chemical Equation Balance

Supplies:

• ruler
• paper clips (colored are best)
• binder clips
• pencil

Directions:

1. Place the binder clips on the opposite ends of the ruler.
2. Count the type of atoms in your equation.
3. Now count the number of each atom and add it to the corresponding binder clip (Use a different color for each element)
4. Use the factor trees to help determine how to best balance the equation by adding atoms (paper clips)
5. The ruler will be flat (balanced) when the number of atoms is balanced.

Using the example from above. This is the balance in action.

Unbalanced equation:

This balance activity uses green paper clips for the hydrogen atoms and blue paper clips for the oxygen atoms.

To balance the oxygen, we added the coefficient to the product side to balance the oxygen.

The result is that hydrogen is now unbalanced. There are 4 atoms (paper clips) on the product side and only 2 on the reactant side.

The balance is leaning to the right.

To completely balance the equation add the coefficient to the hydrogen on the reactant side.

Changes the number of hydrogen from 2 to 4 which completely balances the equation and the balance.

Make learning math fun and easy with these other hands-on activities!

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