Balancing Chemical Equations

Open Ended

Do Now:

What do you think it means for an equation to be "balanced"?

A chemical equation represents a chemical reaction where reactants are transformed into products.

• Reactants: Substances present at the start of the reaction (on the left).

• Products: Substances formed by the reaction (on the right).

Question:
What are the reactants and products in the equation above?

• The law states that mass cannot be created or destroyed in a chemical reaction.

• The number of atoms for each element must be the same on both sides of the equation.

Question:
Is this equation balanced or unbalanced?

Multiple Choice

Is this equation balanced or unbalanced

• Balanced

• Unbalanced

• To determine if an equation is balanced, count the atoms of each element on both sides.

• Subscripts tell you how many atoms of each element are in a molecule.

• Coefficients tell you how many molecules of that compound there are.

Multiple Choice

How many hydrogen atoms are on the reactant side?

• 2

• 3

• 4

• 6

​Sometimes, equations are unbalanced when the number of atoms for each element is not equal on both sides.

Example (Unbalanced):

Multiple Choice

How many oxygen atoms are on the reactant side? How many on the product side?

• Reactant: 2, Product: 1

• Reactant: 2, Product: 2

• Reactant: 2, Product: 3

• Reactant: 3, Product: 1

​Identify elements: Check how many atoms of each element are on both sides.

• Add coefficients: Multiply the number of molecules to balance the number of atoms.

• Recheck each element: Ensure both sides are balanced.

Multiple Choice

How many aluminum atoms are needed to balance this equation?

• 1

• 2

• 3

• 4

Multiple Choice

Is this equation balanced or unbalanced?

• Balanced

• Unbalanced

Multiple Choice

How many oxygen atoms are on the product side?

• 2

• 3

• 4

• 5

Open Ended

Exit Ticket:

In your own words, explain how the Law of Conservation of Mass applies to balancing chemical equations. Why is it important to have the same number of atoms of each element on both sides of a chemical equation?