I am a safety conscience science teacher. I am embarrassed about some of the things that I did in my classes early in my career that I did not realize were unsafe. I saw the demonstrations and activities done at professional development venues and assumed that if my mentors were using the activity, it was safe. Today I am advocating for more preparation in this area for our pre-service teachers and professional development opportunities for current teachers.
Through my years of experience, I have found that students are more engaged in activities that they can make a connection to. If I use chemicals that they are familiar with in their everyday lives, it makes the field of chemistry seem more practical. Fortunately, this practice allows for greener options when teaching chemistry concepts.
Having recently participated in Green Chemistry training through Beyond Benign (discussed in a previous blog), I am trying to clean up some of the labs and demonstrations that I am still using. I mentioned in an editorial I contributed to JCE that I use the dehydration of sucrose with sulfuric acid as a beginning of the year demonstration. The Footprint of a Chemistry Teacher Lesson, published on the Beyond Benign Web site, encourages teachers to reconsider these types of demonstrations. If you ask your students what chemists do, they will most often describe a chemist as someone that blows things up or uses dangerous chemicals. They may refer to the chemistry teacher in the popular TV show, “Breaking Bad”. The lesson suggests that by performing demonstrations like the dehydration of sugar support those misconceptions. The lesson also asks the teacher to consider where the chemicals we use come from, what happens to our waste, the resources (including energy) required to perform the reaction and clean it up, and to consider the complete picture of the footprint we are leaving behind.
I wonder if I need to do the sugar and sulfuric acid demonstration at the beginning of the year. Would it be better to show a video of the reaction and discuss why I am NOT performing it “live” anymore? I could replace it with a hands on activity from the Footprint lesson. The students would add a small amount of yeast to some 3% hydrogen peroxide and measure the temperature change over time. I could introduce reactants vs. products, decomposition reactions, exothermic reactions and catalysts. I will try it this way next time around.
2H2O2(l) --> 2H2O (l) + O2 (g)
I have found many “replacement labs” that I am using this year courtesy of the Beyond Benign Web site. If you click on the site from the link, scroll to the bottom left corner and you will find many replacement labs including the few I am highlighting below. They all support aspects of NGSS HS-PS1 Matter and Its Interactions and HS-PS3 Energy.
Chemical or Physical Reaction – Everyday chemicals replace cupric chloride, 6M hydrochloric acid, potassium hydroxide, and copper sulfate. (Green ideas: Pollution prevention, atom economy, less hazardous chemical synthesis, safer solvents and auxiliaries, use of renewable feedstock, inherently safer chemistry for accident prevention.)
Objectives: Make observations, Inferences lead to conclusions, Define chemical reaction, Define physical reaction, Identify chemical and physical changes.
Exothermic and Endothermic – Everyday chemicals replace the common calcium chloride and ammonium nitrate reactions used by many teachers. (Green ideas: Pollution prevention, safer solvents and auxiliaries, accident prevention.)
Objectives: Define and identify endothermic and exothermic reactions.
Catalysts and Oxygen – Everyday chemicals replace MnO2 and 30% H2O2 catalysis reaction. (Green ideas: safer solvents and auxiliaries, use of renewable feedstock, inherently safer chemistry for accident prevention.)
Objectives: Observe the effect of a catalyst on a chemical reaction and its rate, define reactant and product.