We propose the use of a smartphone based time-lapse and slow-motion video techniques together with
tracking analysis as valuable tools for investigating thermal processes such as the response time of
a thermometer. The two simple experimental activities presented here, suitable also for high school
and undergraduate students, allow one to measure in a simple yet rigorous way the response time of
an alcohol thermometer and show its critical dependence on the properties of the surrounding
environment giving insight into instrument characteristics, heat transfer and thermal equilibrium
concepts.