... We are About to Start Stoichiometry!

All year in Chemistry I use the term stoichiometry to warn my students of things to come, so much so that it has almost become a joke between my students and I.

"I bet all these hard chemical equations make you really excited for stoichiometry!"

"If you think this is a lot of math, wait til stoichiometry!" 

Well, that day has come. We are beginning stoichiometry on Friday. To those who are not familiar with chemistry terminology, stoichiometry refers to the math involved with determining the quantities of compounds or elements in a reaction that are needed for the reaction to actually take place. It sounds more complicated than it is... sort of... It's one of those things that takes some practice but eventually student's get the hang of it. 

Today, we reviewed how to balance chemical equations, since that is what all of this math business is focused on. Tomorrow, it's on to mole-to-mole ratios. 

Before we jump into mole-to-mole ratios, I am going to take some time to discuss how to organize the work for their math problems. Many high school students -- especially those that are not great at math -- have their work written out so that it is messy, hard to follow, and not labeled correctly. They often complain about having to show their work -- "Why do I have to show my work if I just plug it in my calculator?" -- but my policy is No Work, No Credit, No Kidding!  I need to see not only that they got the write answer, but that they know how they got the right answer. 

I feel like this is important time to discuss with students a neater, easier to read way to show their work. Stoichiometry problems can be long and complicated, and this is the only way that I can decipher where they are making mistakes. Each teacher may have their own method of showing work. Some like the fraction version, other's it's boxes... for me I like creating a sort of table to organize my numerators and denominators and provide easy unit cancellation. An example problem is located below, to give you an idea of how I show my students to organize their work. 

When starting a unit that has been built up to be difficult and worrisome (let's face it, the name alone is terrifying), I think its important to give students some structure and go back to review the basics. It's a routine that they need to get used to quickly. My plan is to use this method of showing their work to do some review problems -- mole conversions -- so they see how it works and get into the routine. Hopefully by the time we begin the more difficult problems, they have already seen the merit in showing their work this way and can stay organized! It's so much nicer to have a cohesive method to be able to more effectively spot mistakes and provide help. 

I will let you all know how well my plan works! 

A copy of a mole ratio stoichiometry lab is posted on my Teachers Pay Teachers site. Check it out! Hopefully a post will be up soon about the lab specifically!