If you are testing whether the minimum size has decreased when you heat the liquid one way is logistic regression. You code the DV as decrease/does not decrease (2 levels). Then you have a dummy predictor say 1 if you heat it and 0 otherwise. The t test (the p value) will show if the difference between heated and not heated has a signficant impact on whether the DV decreases or not.

The slope is not very intuitive. If you want to find how much heating changed the odds of being in whatever level of the DV you are maximizing (for example the decrease state if you chose to maximize that in the software) look at the odds ratio. It shows (for a dummy variable) how much the odds of being in the state you maximize increases or decreases (the average difference here between heated and not heated on these odds).

Say you are maximising decrease. And you code the predictor dummy 1 for heated. And the odds ratio is 2. Than if you apply heat you are twice as likely on average to see a decrease than if you don't heat it.