By Dave Vernier
I recently started using an electric pot for heating tea water. Early on, I sometimes assumed that the water was hot enough when I heard the loud “boiling” sounds. Yet, when I poured the water to make tea, it was not very hot.
Our boiling water apparatus
We decided to make a movie and take data to show how sound and visible bubbling are related to the temperature. We used a standard “trick” for synchronizing the movie with the data. Near the start of the movie, we moved our hand in front of the IR Thermometer. This caused a drastic drop in the temperature reading for that sensor, and we can see the hand movement in the movie, so it is easy to synchronize the two. Note that the first bubbling starts about 90°C, too cool for tea connoisseurs. In this experiment, we used two Surface Temperature Sensors and an Infrared Thermometer to measure water temperature as we recorded the movie.
Temperature vs. time as the water approaches boiling