A control experiment for the above

A control experiment is designed to isolate the effect of the variable being tested. In this case, it helps confirm that the observed gas volume change is due to the grasshopper's respiration and not other factors.

The control experiment would use the same apparatus and same conditions as the original experiment, but without the grasshopper. Instead, an inert object of similar volume or mass to the grasshopper could be placed in the flask, or the flask could be left empty but sealed. Compound X would still be present to absorb any CO₂.

In the control experiment, there should be no significant change in the level of colored water in the capillary tube. This is because there is no biological respiration occurring to consume oxygen or produce carbon dioxide.