New year. New goals. One of them being more blog posts, so welcome to Science Sundays! Each Sunday I’m going to write something about science, and classroom activities, instructional strategies, or current events!
This week’s topic will be: Catalyst Investigations! I felt this should be the first ‘Science Sunday’ since my last post was all about the stress of implementing labs and it’s only right to write about the great parts too 🙂
The slow-mo video below shows my students testing a gas that is produced when hydrogen peroxide and potassium iodide interact:
The glowing wood splint reignites as it interacts with the gas being produced by the decomposition of hydrogen peroxide (into water and oxygen gas). While I used this lab to study catalysts, it could also be used for learning types of reactions!
Below are the Oklahoma Science Standards (it’s the same as the NGSS) and the Learning Scale that we were working on when my students did this lab. I combined two standards for this concept because they worked well together.
HS-PS1-5: Apply scientific principles and evidence to provide an explanation about the effect of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs.
HS-PS1-6: Refine the design of a chemical reaction by specifying a change in conditions that would produce increased amounts of product at equilibrium.
5: No mistakes!
4: Identify errors in explanations about the effect of changing the temperature or concentration of the reacting particles on the reaction rate and product production at equilibrium.
3: See goal! (Always the standards)
2: Summarize/illustrate 5 factors that affect reaction rates and equilibrium (concentration, temperature, surface area, agitation, and catalysts).
1: Describe the following terms: Collision Theory, reaction rate, concentration, temperature, catalyst, surface area, agitation, equilibrium, kinetic/potential energy, and energy diagrams.
0: Understand: solutions, Solubility, concentrated vs. dilute solutions, and dissociation.
This particular investigation was done in the middle of the concept, when we were discussing catalysts. We used hydrogen peroxide because most students are familiar with this substance. Using their background knowledge, I asked students to write an equation for an interaction with hydrogen peroxide and potassium iodide, not telling them the KI was a catalyst. Some will immediately know the reaction is decomposition but most will attempt to write a double replacement reaction between the hydrogen peroxide and KI. Don’t correct them if they are wrong! They will test their product predictions during the investigation 🙂
During the investigation students will write ALL observations! No matter how insignificant they may think it is, I tell them to record everything. Once the investigation is complete, I have students compare their product predictions to their observations; are they missing anything? Does it change their answer? Students can talk within their groups, and to other groups. I make sure to listen in on their conversations but my only contributions to their discussions are questions or “I don’t know, what do you think?” Sometimes….well most the time….they would rather just hear the answer but they learn so much more if they come up with it!
During whole class discussion, I make sure to lead them (with questions!) towards a dialogue about the type of gas that was produced. Before revealing the answer, I do a small demo with a piece of calcium metal, water, a watch glass (as a “lid”), and a glowing wooden splint. This reaction results with hydrogen gas as one of the products, and an obvious difference from the reaction they performed in the lab. There will be a “pop” noise as the hydrogen gas ignites, and the watch glass lid will come off. Always an exciting moment 🙂
I really do enjoy doing investigations with my students. They learn so much if they can see the information, rather than trying to imagine the reaction. Chemistry can be difficult to “bring to life” so any time I can find ways to do this makes learning (and teaching) so much better!
Alright, as always if you have questions please let me know! And next week’s Science Sunday will be about Augmenting Reality! Happy teaching 🙂