As I am learning thermodynamics, it is very interesting to see phenomena that I experienced in real-life (cooking, turning on the fan or air conditioner) be explained in detail. It makes me respect these devices more, and makes me grateful to everyone who was involved and smart enough to make these devices.
I remember, when I started learning thermodynamics for the first time, the most interesting part to me from the technical side was the phase diagram. Up until that time, I did not know that phase changes do not happen instantly. I always thought they did, and wondered why, for example, a whole pot of boiling water did not evaporate immediately. I got my answer in detail!