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Mariana Pirillo (Italy): Demonstration of different chemical reactions which produce CO2

Mariana starts by telling us that the teaching in the Italian schools are quite different from what I’m used to. All the lessons are based as lectures, with no room for the students to work with exercises, tasks, experiments, collaborative work etc in the school. This is something the students are supposed to do after school (more like our universities). This means that it can be hard to find enough time to do these hands-on experiments.

But she has found her way – and her recipe for getting the students involved is:

1. Ask a question (or two) – “Why are we interested in CO2?”
2. Get the students to do some background research
3. Then get them to make a hypothesis before doing the experiment
4. Testing of the hypothesis by hands-on experiments
5. Communicate your results

Experiments:

Making CO2 of fizz powder.

1. Weight of CO2 – fill two balloons, one with air (air pump) and one with CO2. Which balloon is most heavy?
2. CO2 in water – what happens with the pH?

Sally (Germany): Demonstration of experiments on CO2 in seawater (solubility, buffering capacity, CO3)

Sally showed experiments that she has used with her 11-14 year old students, but these experiments can be used with students all the way through high school as well.

She starts up with the red cabbage experiment to get the understanding of acids and bases.

Then she addresses the main question for the students:

“Why and how can seawater be a sink of atmospheric CO2?”

Two glass jars – one with freshwater and one with seawater. Add acid (vinegar) and base (soap), and measure the change in pH for every drop that is added. Hopefully the students will see the buffer capacity of the seawater.

“Why has seawater this buffer capacity?”

Blow (CO2) in the glass jars (with/pH sensors in them, close the opening with cotton) until the pH doesn’t change anymore. “Why?”
Compare freshwater and seawater.

Crush some eggshell and put this in the freshwater that is saturated with CO2. Check the change in pH.
Do the same with the acidic seawater, and compare the results. The eggshell will not dissolve in the latter because the pH will not be low enough (it is of course a time issues though…)

Addition of carbonate will raise the pH value again.

It is possible to have an experiment with algae, and see the effect of phytoplankton on pH and CO2.

Solubility of CO2 and temperature

Sally found the idea for this experiment on the internet, but has modified it for her students. Fizz tablets in water, measure amount of gas, compare warm and cold water.

Sally uses these experiments with quite young students, but I can use these with my upper secondary students as well. Interesting.