Why Students Struggle with Limiting Reagents Even with our best efforts, it can be hard for some students to comprehend what a limiting reagent really does in a reaction.  Many high school chemistry students struggle to understand limiting reagents in stoichiometry because they cannot visualize which reactant actually “runs out” first.  In between my first and second Alka-Seltzer chemistry lab yesterday, I introduced a very simple demo that really helped.  Even though I had

Many chemistry teachers introduce the mole right before stoichiometry.Then we’re surprised when students treat it like a complicated conversion trick instead of a way of counting matter.   The mole is one of the most foundational ideas in chemistry. When students encounter it earlier in the year, they begin to see it as a universal counting system — not just a step in reaction math.  Here is why moving the mole earlier changes everything. Teaching the mole early allows studen

Predicting the products of chemical reactions — especially double displacement reactions — can overwhelm first-year chemistry students.  The confusion usually comes from mixing two different skills: writing stable compounds and balancing equations.  Sometimes all it takes is for a single phrase to click in their brain.  I added a new phrase this year that helped students know the difference between writing valid compounds and balancing equations.  This distinction is especial

Students have a hard time learning to determine if single displacement reactions will occur.  In my class, they have not yet seen an activity series.  This year, I gave them a short simple lab, and they had to design their own!  Across all my periods, every lab group was able to design an activity series that matches the reality.  In one block period, their understanding of single displacement reactions went from zero to 100!  Here is the simple lab and activity that I used t

It’s obvious that practice tests are helpful for students.  I love using them to reduce anxiety, improve performance, and ensure each student understands the breadth of the material.  But there are some hidden benefits as well.  Practice tests help you, the teacher!  Here is how giving a practice test for each unit benefits teachers by improving instruction, reducing grading, supporting assessment, and saving time. Structure of the practice test I will briefly describe the st

Have you ever done this?  You finally decide to change a lab, and then wonder, why didn’t I do this years ago?  That was me this week.  For years I used batteries and lights to measure the conductivity of solutions.  I used it in my lab exploring the physical properties of ionic and molecular compound.  But I found that the voltage was too low if I used D cell batteries.  And if I used 9 V batteries the kids would burn out all the lights.  It was a constant battle.  Here is h

Teaching the formation of ionic compounds isn’t hard for most.  But starting with a visual activity before ANY lessons have occurred really helped the struggling students this year. The kids were engaged in solving problems using information they had from previous chapters.  Here is how I built the first part of the unit. Make compounds with manipulatives On the first day of the unit, which happened to be the first day back from Christmas break, I handed out decks of Who’s yo

You made it to the last day of finals! Way to go. If you are like me, your red pen will be moving at 1,000 miles per hour after school today to get finished up. I hope that you are looking forward to some time off. Time to breath. Time to reset. Time to stress about what to do with your children at home. Let me see if I can help. I made a Christmas Break Bingo card. Go ahead, limit your children's (and your) screen time. Pick a square and go for it. Looking back on

“Wait, Mr. Koch, we already knew that!” My student was excited to see how close her empirical formula of magnesium oxide was to the correct answer.  Did she already know the formula? Yes, yes you did.  And that is the magic of how chemistry builds on itself.  Students could figure out the simplest ratio from looking at the valence electrons.  Or they can do the reaction to see the ratio appear in mole ratios.  Don’t overlook a topic as too simple when it allows students to m

Kids love rockets. Kids hate math. Kids love competing. Kids hate calculating.                The rocket lab keeps the things that kids love, and then surprises kids with the satisfaction of the things they hate.  It is my favorite lab of the year, making hydrogen and oxygen rockets and launching them down the hall.  But the real magic happens the day after the lab.  I wrote a blog about the lab setup a couple years ago.  You can check it out here.   I’m going to focus on wha

The periodic trends unit can feel a bit repetitive.  I only do one lab to start the unit in which the kids discover the reactivity of the alkaline earth metals.  After that, it can be a bit of a slog through all the different trends.  Until now!                I have started a cycle through this unit that has become very successful.  It only relies on 10-minute lectures and lots of discussion and activity.  The cycle goes like this: 1.       Teach 2.       Model 3.       Play

Don’t you feel a little dumb when you discover a tip or trick that makes your life more efficient, and it was right in front of your nose all along?  Today’s article is super short, but makes a big difference in efficiency.  Here are two simple tricks to make you more time efficient as a chemistry teacher. 1.       Write the formula of the compound on the lid I’m probably going to discover through feedback that all of you have been doing this since the 1980’s and I’m just an

I love competition in the lab.  Especially at the AP chemistry level.  Every year I have the students compete to see who can get closest to the correct molarity in the “Titration of X Molar Strong Acid Lab.”  The kids love competing to see which group can land on the faintest pink solution.  They will fight to the half drop of sodium hydroxide to win that one.  I told them that other teachers post pictures of good results on social media.  They kept asking, “Is this titration

Yesterday, I used flame tests along with a two brief lessons in an effective block period.  I have always felt that flame tests can get lost in the “oooooo, cool colors” caliber of chemistry.  And then they don’t mean anything intellectually to the kids.  This year I combined two short lessons and sandwiched the flame tests in between. I completed it all in one 90-minute block.  It made a more powerful lesson.  Here is how I did it.  Plus, download the free lab write-up here

I was looking for a way to review the periodic table during the atomic structure unit.  And I found it!  A simple game of “Atomic Guess...

Chemistry students can struggle to connect with how the two classic atomic experiments worked, Thomson’s cathode ray tube and...

Beer’s Law is used all over chemistry. This week I used it in both AP chemistry and grade level chemistry.  But in order for my AP kids...

Molecular polarity is an important concept.  It’s also a concept that I have primarily described with words.  This year, my teaching...

I taught density to my grade level chemistry class this week.  Have they learned density before?  Yes.  Do they use the concept of...

To allow retakes on tests or not allow retakes, that is the question. This question stirs up a bunch of deep conversations about...