TITLE: The Law of the Conservation of Matter

PURPOSE:

BACKGROUND INFORMATION:

The law of conservation of matter states that during a chemical reaction matter can not be created or destroyed (meaning atoms can’t be created or destroyed). This means that any atoms that are present at the beginning of the reaction must be accounted for at the end of the reaction. This is done by balancing the equation for a specific reaction. For example, if you burn a piece of paper, the black ashes appear to have less mass than the original paper. The paper is made up of carbon, oxygen, hydrogen and some minerals. As the paper burns it produces water vapor and carbon dioxide. All the atoms of the paper can be accounted for in the ashes (the minerals), in the gases (carbon dioxide) and the after vapor that were released when it burned. So no matter has been destroyed. This reaction is shown by the following equation:

C6H10O5 + O2 CO2 + H2O (not balanced)

However, this equation does not obey the law of conservation because there are atoms on the reactants side of the equation that are not accounted for on the products side of the equation. In order for this reaction to obey the law of conservation the equation must be balanced. The balanced equation looks like this:

C6H10O5 + 6O2 6CO2 + 5H2O

All the atoms that are present in the reactants are accounted for in the products. This was done using coefficients to show that in the reaction multiple molecules of some substances will be involved.

In this lab you will burn matches and conserve all the by-products of the reaction.

IT IS EXTREMELY IMPORTANT THAT YOU FOLLOW THE SAFETY PRECAUTIONS!!!

PROCEDURES:

Tie the matches together using the sewing thread and place them in the bottom of the flask as shown in the picture. Insert the stopper in the top of the flask with some of the thread hanging out to keep the matches up. Make sure you have a tight seal with the stopper. Determine the mass of the flask and record to the nearest hundredth of a gram and record.

Place the flask on the hot plate with your hand over the top of the stopper (make sure you are holding the hot hand). Hold the flask on the hot plate until the matches ignite and burn. As soon as the matches go out remove the flask from the hot plate. Make sure you are holding the stopper in place with the hot hand the whole time! Do NOT open the stopper. Again determine the mass of the flask to the nearest hundredth of a gram and record.

Clean up lab station.

DATA TABLE:

Mass of the flask and matches before burning ______g

Mass of the flask and matches after burning ______g

QUESTIONS:

  1. What did you expect to be the difference between the mass of the flask before and after the matches have burned before you performed the experiment?
  2. What changes did you observe to indicate that a reaction took place?
  3. What is the difference between the before and after mass?
  4. What explains the relationship between the mass before burning and the mass after burning?
  5. If there is a difference between the mass before and after the matches have burned, why do you think this is so? If there is not a difference between the masses skip this question.
  6. If there is not a difference in mass, what do you think might cause a difference in the masses?