CoM PIT-BC continued

We are now finished with the exploratory part of the week.  Now it's time to start designing our main experiment.

Some of you noticed that as the Alka Seltzer reaction occurred in the stoppered flask, pressure built up and the stopper sometimes popped off.  When that happened, all of the gases were able to escape, making the flask just as bad at conserving mass as the beaker. For our actual experiment, I will ask you to try to design a container that will definitely trap all of the gas so that we can measure it.  I will give some suggestions of materials to use during class.  The problem statement for our PIT-BC will be 'What is the affect of the type of container on the conservation of mass?'  where the experimental variable (the thing that we are changing) is the type of container, and the dependent variable (the thing we are going to measure) is the conservation of mass.  We will also be switching from the Alka Seltzer and water reaction to the well-known baking soda and vinegar reaction.

Today in class, we will be working on writing instructions for the lab and, if we have time, we will make our data tables and write our predictions.

Conservation of Mass PIT-BC

This entire week (and maybe next week) will be dedicated to completing our second PIT-BC of the semester.  This project will be set up exactly like your semester test.

First, we will complete an exploratory activity on Monday and Tuesday.  This lab will introduce you to the concept of the conservation of mass by looking at the reaction of Alka Seltzer and water.  The Law of Conservation of Mass says that the amount of reactants in a chemical reaction is equal to the amount of products;  matter cannot be created nor destroyed.  In other words, the mass of the stuff that you start out with has to be the same as the mass of the stuff you end up with.  We will discover that when the Alka Seltzer reaction takes place in an open beaker, much of the gas that is produced just escapes into the air.  Because of this, we cannot accurately measure the mass of all of the products, so it appears that mass is not conserved in the reaction.  However, when we complete the reaction inside of a flask with a rubber stopper in it, that gas is trapped and we can measure the mass of all of the products.

Here is a link the the exploratory activity