Can you picture the giant stack of lab reports that you still haven’t graded? Maybe they have a digital notebook and you haven’t clicked through them all yet.
Don’t grade them. There, I said it. Don’t grade them.
Instead, I have started using lab practical exams as a way to measure their understanding of labs, check on the thoroughness of the their calculations, and quantify their understanding. Here are a few ideas that will help you reduce your lab grading efforts as well as increasing their concern about the quality of their lab work throughout the year.
Use small challenges
In one class period, I will use two or three small lab challenges. These are not full labs, but rather parts of previous labs that they have done before. As an example, early in the year, we create alum, measure the percent yield, the melting point, and the hydration ratio. During their lab exam I only had them calculate the hydration ratio of a compound. It still allowed me to see how well they understood their lab during the semester, but it didn’t take days to complete.
Don’t give instructions
During the lab exam the only materials that they may access are the methods and calculations that they put in their digital notebook. They work alone. They may not help each other. They may not use handouts. This ensures that the methods and the results sections of their lab notebooks are written well. It becomes incredibly obvious when the student had a bad notebook. They are trying things that way off the wall.
Put a time limit
Force the students to work under pressure. It makes them get crystal clear on what they are trying to accomplish really quickly. It also forces them to work fast enough that they don’t have time to cheat. By the time they realize they don’t what they are doing and the person across the table does, they don’t have enough time to redo the whole lab. This also increases the level of concern that the kids have. Yesterday, during my AP chem lab test, a student came in to deliver something and said to me, “I’ve never seen such a quiet lab before.” That’s called fear. They were so laser-focused that they didn’t have time for chit-chat.
Grade methods heavily
The challenge with any lab is that a kid can do the correct thing and still get a wrong answer. That is why I grade their lab exams 70% on their methods. Did they correctly choose and communicate the exact steps that would lead to a correct answer? If they did, they will do well on the test. The primary goal is that they understand what they did in the past and be able to put it into action.
That leaves 30% for results. Of that percentage, some of it is given to correctly showing their work and displaying their results in the right form. Did they make the correct excel spreadsheet? Did they put the independent variable on the X axis? Did they remember to convert to moles? The rest of their results score comes from how well they did. If they got a horrible answer because they chose a horrible method then their grade should reflect that. I had a student choose a really bad method for solving one of the problems. The correct answer was 4.34%. She got 85. She shouldn’t receive all the results points for that.
Include distracting items
Include some materials that are available to them that are just red herrings. This helps ensure that their methods from early in the year are precise. Yesterday, they had to do a titration. They know that they need an indicator and that the final color will be pink. So what did I do? I dug in my chemical supply cabinet and found a pink cellular dye that was in a dropper bottle the same size as phenolphthalein. Among other, more reasonable, indicators, the pink one looked obvious. Fortunately, no one took the bait. And they didn’t because their methods included what indicator to use.
Ask unique questions
I like to ask questions that are lab adjacent. It is a skill that they learned from their prior lab, but the test forces them to put that skill into action. For example, during the titration lab in the school year, they had to calculate the molar concentration of an unknown strong acid. For their test, I asked how many grams of sodium hydroxide I added to make 1.0 L of solution. To you and I, it is the same question. But the kids are forced to decide if they need to switch the titrant and indicator or not. This leans into their understanding of the lab. I also asked a question that included Le Chatelier’s Principle and spectrophotometry. They hadn’t done a lab with both of those skills together. Instead, they had to pull their spectro knowledge from one lab and the Le Chat from another.
Make it a milestone
I bet if you think back to your college experience, there were a few labs that stand out. For me, they were ones with pressure. The hard tests that we survived. Those are milestones in my mind. If you create enough hype and tension surrounding the lab practical test, when the kids survive, and they will, it feels as though they have crossed a threshold into science knowledge. The kid who delivered the note and asked why it was so quiet said one other thing too. She asked what class it was, and I told her AP chemistry. “Oh, I could never do that.” The students heard her say that, looked at each other and smiled, and then went back to solving their problem because there were only 11 minutes remaining and the clock was running. They crossed the threshold and they are proud of it. I’m proud of them, too.
Want more ways to make your class feel engaged and focused? Try using classroom games that actually benefit your curriculum. Don't waste time. Let games create conversations that create understanding.
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