Science Buddies: "Ask an Expert"

I'm planning to conduct the 'Swimming in acid: Ocean acidification' experiment listed under 'Science Projects' and was wondering what the significance of screwing the lids on is. Does it affect the experiment results in some way if I unscrew the lids to check the mass of the shells on a weekly basis, or, is it best to only check the mass at the start and end of the 4-week experiment, and not in between?

Hello,

This sounds like a great project! It is important to prevent the CO2 that is dissolved in your "ocean water" from escaping from the jar into the air. If the CO2 escapes you'll have less carbonic acid formed and your results won't be as accurate. It's best to fill the jars as full as possible to prevent any air space above the liquid level and the lid and then only open the jars again at the end of the 4-week experiment. I know it's a long time to wait for results!

Good luck,

Audrey