May 2024 newsletter: Solubility rules, site license renewals, end-of-year survey, and more!

Hello again! For everyone who’s almost done with this school year, I hope that it’s wrapping up well for you and your students. In this newsletter, I’ve included the following important updates about

  • *NEW* Solubility rules questions!
  • End of the school year survey – win a $50 gift card!
  • Site license renewals for 2024-2025 school year
  • IMPORTANT annual site maintenance starting July 1st
  • Bug fixes and other improvements

*NEW* Solubility rules questions!

The primary goal I had when I created back in 2020 was to provide a useful and accurate resource for Chemistry teachers and students. As the site has grown and become more popular, I’ve tried to fill in some of the gaps that exist in the quiz topics, which can sometimes be a real challenge, depending on the topic.

I just added a topic that was long overdue – solubility rules! In the Solubility Quiz, you can now have students predict whether an ionic compound will be soluble, slightly soluble, or insoluble in water under standard conditions. Just select the new option, “Determine solubility of a compound in water” when generating a quiz or creating an assignment:

Screenshot of options for Solubility Quiz

This option will generate multiple choice questions like this:

example questions from the Solubility Quiz

The Solubility Quiz pulls from 400 different ionic compounds in the database to generate these problems, so there should be plenty of practice for your students. Thanks to Seth, Auburn and Andrew for suggesting this feature!

One of the more frustrating things about creating quizzes that generate random questions about chemistry is that there’s often disagreement between different resources. With respect to solubility, I’ve found that some lists say that lead(II) halides are insoluble, while others say that they’re slightly soluble. I tend to go with the values on Wikipedia since I know there are lots of amazing chemistry nerds out there who make sure those pages are as accurate as possible, but I thought this would be a great opportunity to try out a poll! What do you think – are lead(II) halides (e.g. PbF2, PbCl2, etc.) insoluble or slightly soluble?

(PLEASE NOTE: The poll is only available on the email version of the newsletter.)

Let me know what you think! I want the site to be as useful as possible to you and your students, so I appreciate your feedback.

Complete a survey, enter to win a $50 gift card!

For the past three years, I’ve asked every teacher that uses or has signed up for the Dashboard to complete a short survey about how they use the site and what new features they want me to work on. The feedback has been really helpful!

Every teacher who fills out the survey will be entered into a drawing for a $50 Amazon gift card! Only one entry per person, please. The drawing will be on June 15th, so don’t delay! You can fill out the survey here.

Most site license renewals due July 1st

Thank you to everyone who has already renewed their school’s site license for the Dashboard for the 2024-2025 school year! Site licenses are how I pay for the web hosting and the software I use to write the quizzes, and it keeps the website ad-free. I’ve sent out invoices for next school year to everyone with a current site license, but if you didn’t receive one, please let me know.

You can check your school’s site license status by going to the Dashboard and clicking on “School Info” in the top menu.

Once your site license for the Dashboard expires, you won’t be able to create new student accounts, classes or assignments. If you plan on renewing for next school year but you need a little extra time for the paperwork to go through, just drop me a line and I’ll extend your school’s expiration date. I’ve taught in three public school districts over my career and each handled purchase orders differently, so I understand how complicated the process can be.

If you currently have a demo account and would like to purchase a site license for the 2024-2025 school year for just US$70, you can do so right now in one of the following ways:

  • credit card through Square (the most popular option)
  • school purchase order (contact me for a sales quote – I’m also happy to fill out any paperwork required by your institution or state)
  • personal check
  • CashApp, PayPal, Venmo or Zelle at

Additional schools in the same district can purchase an add-on license for 50% off at just US$35 per school. If you also teach physics or you have a colleague who does, you can bundle a site license for the Dashboard for just US$35 more! Please contact me if you have any questions about how to purchase a site license.

Site licenses also help me offer the Dashboard for free to 143 public schools in the U.S. with high rates of poverty. If you teach in a high poverty public school or school district (at least 50% of your students on free/reduced lunch or designated “economically disadvantaged”), please send me a link to the supporting documentation and you’ll get a free site license for the Dashboard forever.

Important annual site maintenance

Over the past four years, has added more schools with more students who generate more quiz results, so every summer I have to archive older material to keep the site running efficiently. For example, there are currently over 355,000 quiz results from this school year in the database so far, which is a 152% increase over last school year’s total! 😱

I’m going to be performing the following maintenance items over the summer, starting on or shortly after July 1st:

  • All students accounts, assignments, quiz results, and classes created during the 2023-2024 school year (7/1/23 – 6/30/24) will be archived (but not deleted)
  • All student accounts created during the 2022-2023 school year will be deleted

Items that are archived will still be accessible to you through the Dashboard. If you don’t want me to archive your stuff, or if you operate on a different school calendar, please let me know before July 1st! Also, I perform regular backups of all data on the site, so I can always restore anything you might need.

Bug fixes & other improvements

Thanks to all of the teachers and students who send in bug reports and suggestions for improving! Here are all of the updates I’ve made since the last newsletter:

Dashboard – these features and bug fixes also apply to!

  • improvement: added link to renew site license on “Your School” page
  • improvement: added an alert about “require login” and “save progress” options (thanks, Nate!)
  • improvement: changed Dashboard page titles in web browsers for more accurate bookmarking
  • bug fix: trying to create an exam led to a “Column ‘quizID’ cannot be null” error (thanks, John, Matthew and Nick!)
  • bug fix: using the bulk actions menu without selecting assignments first gave a MySQL error (thanks, Yvonne!)

Balancing, Identifying & Predicting Chemical Equations Quiz

  • correction: FeCl2 + O2 -> Fe2O3 + Cl2 was balanced incorrectly (thanks, David!)

Chemical Equilibrium Quiz

  • bug fix: removed several divide by zero errors that were causing the quiz to crash in PHP8

Chemical Thermodynamics Quiz(thanks to Mary Ann for all of these!)

  • bug fix: ∆S word problems involving grams were using moles value instead of mass value
  • bug fix: ∆S problems were mixing up ∆H with q
  • bug fix: ∆S problems had incorrect units in some solution setups

Concentrations & Colligative Properties of Solutions Quiz

  • bug fix: units were missing in dilution problems (thanks, Maggie!)
  • bug fix: given values were being rounded too much in certain situations (thanks again, Maggie!)
  • bug fix: correct answers weren’t being rounded correctly, which sometimes affected scoring (thanks, Michele!)
  • bug fix: blank word problems were being generated for some freezing point depression problems (thanks, Andrew!)
  • bug fix: dilution problems were sometimes being generated with moles as the solution unit (thanks, John!)

Enthalpy Quiz

  • bug fix: formulas for hydrates were showing up with incorrect formatting

Naming Compounds & Calculating Molar Masses Quiz

  • improvement: added 105 new compounds (beryllium, caesium, cadmium, gallium, gold(III), nickel(II), rubidium, vanadium(III), thiocyanate) to the database
  • bug fix: blank multiple choice options were sometimes being generated

Nuclear Reactions Quiz

  • bug fix: reactions with double beta decay mode would cause the quiz to crash when generating multiple choice options

Organic Nomenclature Quiz

  • bug fix: carboxylic acids weren’t being displayed in quiz when they were the only compound class selected (thanks, Matthew!)
  • bug fix: carboxylic acids weren’t being scored correctly (thanks again, Matthew!)

pH & pOH Calculations Quiz

  • bug fix: small numbers (e.g., 1e-14) were not being formatted properly for scientific notation (thanks, Tony!)

Redox Reactions & Net Ionic Equations Quiz

  • bug fix: coefficient for hydrogen ions in redox reaction between iodate ion and hydrogen sulfite ion was incorrect (thanks, Lan!)

Solubility Quiz

  • new feature: classify ionic salts as soluble or insoluble in water using solubility rules (thanks Seth, Auburn and Andrew!)

Stoichiometry & Limiting Reagents Quiz

  • bug fix: quiz was some correct answers as incorrect when they were in scientific notation (thanks, Karen!)

Thermochemical Equations Quiz

  • bug fix: clicking the “Load More Problems Like This” button would cause the quiz to crash 🤦🏻‍♂️

Other improvements

  • maintenance: made lots of “under the hood” code improvements to the quizzes to prepare for server software upgrade this summer

Please keep submitting your bug reports and suggestions! It makes it much easier to fix things when people tell me about them, and has improved a lot over the past four years because of all the teachers and students who have reached out to help.

Help me share with the world!

If you like using, there are three quick and easy things that you can do to help me promote the site!

  • Add your school to the list of supporters on the About page! Simply go to the Dashboard, click on “Your Info” in the top menu bar, activate the box next to “Display School on“, and click the “Update Your Info” button.
  • Tell another Chemistry teacher about and encourage them to try out the Dashboard!
  • Follow @ChemQuizDotNet on X (formerly Twitter), Facebook and Threads and share my updates with your fellow Chemistry teachers!

We only have two more weeks until semester exams at my school, and then I get to take our Environmental Club to the Ohio Envirothon Competition for the fourth year in a row! This year’s state competition takes place in June at Hocking College in Nelsonville, Ohio, which is in the southeast corner of the state and has some of the prettiest landscape around. I know I mentioned this last spring, but if you’re in the U.S. or Canada and your state or province participates in the Envirothon competition, I highly recommend getting involved!

Thanks again for all of your support, suggestions and feedback over the past four years! Working on with so many great science teachers from all over the world has been an awesome and uplifting experience. Please feel free to reach out any time via the Contact form or at if you have any questions, comments, or concerns. Take care, stay safe, and for those of you in the United States and Canada, good luck with the rest of this school year!