Writing and Balancing Chemical Equations
The Law of Conservation of Mass was established in 1789 by the French chemist Antoine Lavoisier. This law states that mass is neither created nor destroyed in any ordinary chemical reaction. A simpler way of stating this is to say that the mass of the substances produced (products) by a chemical reaction is equal to the mass of the reacting substances (reactants). View this presentation to learn how to balance a chemical equation.
View a printable version of the interactivity.
To help you in your study of balancing chemical equations, it may be helpful to access the Balancing Chemical Equations simulation from PhET Interactive Simulations. Make sure to click on the link for the introduction once you reach the interactivity's website. Make sure to complete all three simulations to make ammonia, separate water, and combust methane.
Strategies for Balancing Equations
Balancing chemical equations will take some practice. While you are practicing, it is helpful to have some strategies to help you learn how to write and balance chemical equations. Take some time to review the four strategies below and make note of them for further use.
- Often, an equation can be balanced by using the subscript for the element on the left side of the arrow as the coefficient in front of the formula containing the element on the right side of the arrow and vice versa.
- The pure nonmetallic elements (hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, selenium) can be temporarily balanced with a fractional coefficient (1/2, 3/2, 5/2, etc.). If you do use a fraction during the balancing process, you can eliminate it later by multiplying each coefficient in the equation by the fraction’s denominator.
- Polyatomic ions do not change in the reaction, and therefore appear in the same form on both sides of the chemical equation. Polyatomic ions are balanced as if they were single atoms.
- If you find an element difficult to balance, leave it for later.
Now, try the game based on your studies of balancing equations. Access the Balancing Chemical Equations online game from PhET Interactive Simulations. Make sure to click on the link for the game once you reach the interactivity's website. Your mastery of this game will help reinforce all of the information that you have learned in this topic.
Balancing Chemical Equations Review
Now that you have learned how to balance chemical equations, complete this activity to check your knowledge. Answer all of the questions by following the directions provided with each question click SUBMIT to check your responses. Click on the interactivity thumbnail, and then click NEXT to get started.