Investigating Ocean Acidification
This page provides a variety of experimental ideas for investigating ocean acidification.
Place some universal indicator into some water.
Blow bubbles into the water through a straw. The solution should turn from green to red, indicating a more acidic pH.
Alternatively, measure the pH of your tap water, then place the water in a SodaStream and add the pressurised carbon dioxide. Now measure the pH. Does the pH change with different amounts of CO2?
Introductory videos on chemistry and ecological impact.
Paul Andersen (Bozeman Science) explains Ocean Acidification and the chemistry behind it (5 mins. 5 sec)
Paul Andersen (Bozeman Science) explains Coral Bleaching and the relationship with rising temperatures and ocean acidification (4 mins 44 sec)
The impacts of ocean acidification on biodiversity (12 mins 13 sec)
This is quite a slow investigation and requires a lot of patience from the students. You therefore need to provide coaching to students with limited patience.
If you want to do this as a demo lab, then you can reduce the number of repeats and then evaluate it, or you could do the extreme pH solutions only (this would then not be a relationship but a difference experiment, in terms of stats)
This video shows some simple classroom experiments from The Royal Society.
Things to consider:
As you are looking for a relationship, you will need at least 5 different pH solutions.
You should research an ideal range. It will be from pH 8.5 down to pH 3. This is not a realistic model, but you are aiming to speed up the process. It is the Hydrogen ions that are important in this reaction, so any acid can be used, e.g. HCl. You can even use vinegar.
You can use seashells - they can be bought from garden/deco shops.
Or you can use pieces of limestone.
Prepare at least 5 containers for each pH you are using.
Weigh your shell/limestone and place it in one of the containers. Make sure the mass is carefully labelled and recorded.
As there is a chemical reaction happening between the shell/limestone and the acid, you should consider changing the solution on a daily basis.
If changing daily, you can weigh the shells to be able to calculate the rate of change in mass.
The experiment will need to run for at least 2 weeks to have a noticeable change in mass.
The shells need to dry before being weighed again. This can be done in a drying oven (recommended) or left to air-dry for a few days.
Think about what data you are going to plot. Remember it is always a good idea to use a box-and-whisker plot for each pH to check the variation in the data.