I run one of those distributed computing programs in the background of both of my computers. It uses the processing power that you aren’t to do work for a Great Cause (like searching for a cure for cancer, indexing articles for history, human genome stuff, etc.). When I run it, my laptop runs very hot; when I close it, it cools off dramatically. There are no moving parts to cause friction in a microprocessor (unless Intel goes back to coal-fired computers 
), so why does it get hotter? I thought the entire processor was always “on.”
Semiconductors are designed to be efficient in terms of power consumption, meaning that they draw more current from the system power supply when there is more work to be done. This was first made practical by a transistor circuity design called complimentary symmetry. The theory is complex, and I can’t even think of a way to describe it to anybody who hasn’t studied discrete amplifier design, but basically the components act as switches, taking turns switching on & off to accomplish work. The more often they switch on, and the longer each device stays in a switched-on state, the more current is drawn from the power supply (and the hotter everything gets).
The earliest amplifiers were always on (called class A), and always drawing current even when there was no work to be done (like when the volume was low). Then came class B, the push-pull amplifier. It was normally off cold, until work needed to be done (like when the volume was turned up). Then the power-hungry transistors turned on and began to do their job. Remove the signal, and the transistors turn themselves off. Very efficient.
This advance in amplifier design has resulted in much of the consumer technology craze of the 80’s & 90’s. With consumer electronics devices smarter and power-efficient, a much smaller battery could be used to make just about everything portable. The Sony WalkMan™ would have never been practical without the class B amplifier (and subsequent improvements on class B operation).
That brings up another point. Most of the heat you are sensing is probably coming from the power supply, not the processing chip (although the chip does get hot too). The supply is getting hotter pumping out the extra current demended by the load.
Analogy: when you drive a car, you are the µprocessor (making the desicions, directing the hardware to do this or that) and the car’s engine is the power supply. When you are towing a heavy load up a steep hill, your pulse might race a little and you might even break into a nervous sweat, but the real heat comes from the source of the power (the engine).
Simply put, the components just work harder and therefore get hotter.