Something wonderful happened yesterday. My room was full at lunch. I mean really full. And all of them were helping each other to understand the labs that we had completed all semester. They were comparing their calculations. They were making sure their methods were complete. They were assuring themselves that they could graph in excel and create accurate models. They were doing all the things that you would hope a student would do with your lab, but rarely does. Why were they doing this, you ask?
Lab finals.
Yesterday was the day for their lab final. On the lab final, the only tool that a student may use is their lab notebook. Whatever they have put in there, they may use. The lab final is a small lab activity with no instructions. The only methods they have are what is in their lab notebook. If they took good notes, their grade will be good. The opposite is also true. In AP chemistry, they get three problems to solve in 90 minutes. In AP biology and grade-level chemistry it is only two. I choose new challenges each year to coordinate with the labs they have done.
Lab Final Set-up
I like to make challenges that are lab adjacent. What I mean is that the student will know what lab to use to get the methods, but there is some small tweak. They have to change a unit. They have to run it backwards. It is endothermic instead of exothermic. Something to make them dig in and really have to understand how to manipulate data. Below, I will share my 2024 AP chem lab final. Hope you enjoy it as much as they did. (I’m joking. Every year during lab final time, there are a few shed tears. Then they actually solve the problem. And smile about it later.)
One final note, I always put extra chemicals, extra glassware, etc on the cart for them to look at. It forces them to choose the right equipment, like indicators, measuring devices, sizes of glassware etc. It also points out the students that have no idea what is going on.
Lab Final 2024
During this standard block period, you are tasked with solving all three of the following problems. You will be graded based on your methods (70%) as well as your results (30%).
You may use any common lab equipment available to you. You are responsible for the safety, care, and cleaning of all chemicals, lab equipment, and self.
In order to solve these problems, you may use your previous lab write-ups. You may not work together and you may not utilize internet or other sources.
1. Calculate the number of grams of sodium hydroxide mixed into 1.00 L of deionized water. You are given a known concentration of hydrochloric acid. Record your results to correct sig figs.
2. Calculate the hydration ratio of copper CuSO4 ∙ nH2O.
Record your methods carefully. Record your answer to correct significant figures.
CuSO4 ·________H2O
3. Calculate the enthalpy of dissolution of ammonium nitrate in kJ/mol. When ammonium nitrate dissolves in water, there is an enthalpy change. Calculate that energy change in kJ/mol. Make sure that you have the correct sign on the answer.
As you can see, this lab final made them use a variety of different lab skills; titration, stoich, and coffee cup calorimetry. There was also an element of novelty in #1 and #3 for them. They have done multiple different titrations. But I had always given them the concentration of the base. And when I give them concentration, it’s always in molarity. Now they had to solve for the concentration of the base in an unconventional unit. This forced them to think about how they would set up the lab, what indicator or probe to use, and how to manipulate the units.
The hydration ratio lab was very similar to one they had done earlier in the year. No surprises here, just some good old lab math to keep track of.
The coffee cup calorimetry lab was unique in that they had done it to calculate the specific heat of an unknown plastic. They had done it to calculate the heat of a reaction. But they had never heard the phrase “enthalpy of dissolution”. They had also never done an endothermic reaction. This forced them to analyze their data in a deeper way.
I highly recommend using lab finals, (if you want to read another blog about the benefits, check it out here) especially for honors and AP classes. It increases their concern for each lab, improves lab notebook quality, and then builds confidence that they can do real chemistry. On their own. Oh, and it reduces the grading load on you throughout the semester. Sounds like a winning process to me.
PS: This is just a fun story from this year. A student came to me on Lab Final day and asked, “Mr. Koch did you tell this year’s class that I cried during the final last year?”
“Yes.”
“Why did you do that?”
“Did you cry during the final?”
“Yes.”
“Did you do your titration upside down and tip over a beaker during the test?”
“Yes.”
“Did you redo it and then get the right answer?”
“Yes.”
“Then your tears are an inspiration to kids who are about to cry.”
“Oh. I am pretty inspirational.”
I love labs. But it is hard to have an on-topic, beneficial lab every week. That is why I created Stoich Decks games. They engage students in a different way, but are still beneficial to the curriculum. In fact, I plan my lesson around the best way to schedule games for the students. Check them out.
I'd love to get more examples of questions you ask on a lab final. Also, do you have some that are appropriate for biology students? I'd love to get examples of those as well.