Science Buddies: "Ask an Expert"

Hi there, I was curious why the shells seem to have gained weight now the the experiment is over from the time that I had started? the ones in the water that was more acidic have gained about the same about of weight as the ones that weren't in the acidic water.

I also am not sure what the variables should be?

Hi Lyndsay,

What were the pH values of the solutions in both the control and acidic samples before you put the shells in? The shells can gain a little bit of weight naturally through the absorption of water (assuming they are relatively dry before immersing them prior to the experiment). If the pH values are too far from what the experiment suggests, the weights at the end of the study may not be too different.

The independent variable for this study is the acidic or neutral treatment. The weight of the shells at the conclusion of the experiment depends upon the pH of the water, so this will be the dependent variable.

Hope that helps,
Pharma