Are chemicals dangerous?

One consistent piece of feedback that I receive from students is that we need to do more “labs” with “real chemicals.” Students seem to have this picture in their mind of a “real” science class with bunsen burners, bubbling beakers, and clouds of smoke that my standard 1950s build tables and chairs inevitably fails to live up to.

Students think of “chemicals” as things that are dangerous, kept in bottles, and only accessed at special times for special experiments. I have found this idea that “chemicals” are dangerous to be so pervasive, I decided to start my chemistry (matter/energy) units with an activity about what chemicals really are and whether or not they are dangerous.

This lesson is a good introduction and helps with student engagement, even though it does not directly align with a specific Texas Science Standard or Next Generation Science Standard. The best fit for the NGSS I could find was

MS PS1-3 Gather and make sense of information to describe that synthetic materials come from natural resources and impact society

And for the TEKS

8.3(A) analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, so as to encourage critical thinking by the student.

I start the lesson by posing the general question “what is a chemical?” and then transitioning to “are chemicals dangerous?” We leave the answer to these questions as an open point for debate and I [using an ominous voice] ask students if they have heard of Dihydrogen Monoxide – one of the deadliest substances know to man. Dihydrogen Monoxide is associated with:

• death by asphyxiation (especially through drowning)
• air pollution
• climate change!

You might not know it, but Dihydrogen Monoxide has been found in cleaning products, industrial wastes, factory farming and, yes, even in the foods you eat! I show the students this website for full elaboration and details on the efforts to bring awareness to this harmful chemical:

What other chemicals may be lurking in the world around us that could possibly cause us harm? Teens can make a difference in saving the environment, and possibly lives, through regulation! I show this video of teen advocacy in action:

Now I charge the students with investigating some common chemicals and creating posters, speeches, or other advocacy materials that state whether they think the chemical should be allowed to continue unregulated or banned by the US Food and Drug Administration.

This is also a good time to review science safety and introduce students to the Safety Data Sheets or SDS (formerly known as the MSDS) for chemicals. Each group gets a different SDS for their research. NOTE: DO NOT LET STUDENTS USE COMPUTERS FOR RESEARCH….the students will find the “common name” for the chemicals and the “big reveal” will be foiled!

The key to this activity is that the SDS pages you are giving out include the scientific names for common chemicals that we use regularly in our everyday lives. When something sounds “science-y” it becomes scary – very few people would hesitate to take an aspirin, but many would balk at being asked to ingest acetylasalicylic acid. There are lots of fancy words on the SDS, so students usually need some help interpreting the meaning (this also gives you a good chance to check background knowledge and vocab!). I usually have students focus on the last section with “additional notes” where I’ve added in some possible “dangerous” reasons that the chemical could be banned (or not).

After the amount of time for the poster/notes/speech creation is over, we either do a gallery walk or share as a class (1) what the chemical is (2) whether or not the chemical should be banned and (3) why.

We circle back to Dihydrogen Monoxide. Let’s think about this a bit….”Di” means two – like to “di-vide” something in to parts. “Mono” means one. What is something that we know of that has two (di) hydrogens and one (mono) oxygen? H2O – Dihydrogen monoxide is water! We must agree that water is extremely dangerous and everything that I and the website said about water is true, but should we ban water? Probably not. Is water a chemical? Yes, it is!

So….what were those other chemicals the students were examining and possibly banning? Click here for a GoogleSlides Presentation with the “big reveal!” or download the presentation below.

This presentation usually gets some “oooohhhhsss” as we discover that everything around us is actually a chemical. Humans are made of chemicals. Our food is a made of chemicals!

I like to end the lesson by showing students the beautiful posters created by James Kennedy, a teacher in Australia. His “Ingredients of the All Natural….” series lists the “chemicals” that make up the “natural” foods we eat. Good food for thought!

Good science involves gathering data, thinking, and reasoning. In this lesson we’re trying to get students not to make assumptions based on prior beliefs, but to always do research, gather data, and consider many alternatives. As an extension, you can have students do research on some chemicals that HAVE been banned or are controversial. A recent story from NPR about Fluoride can be a good jumping off point. Enjoy!