A large Pyrex flask of water is heated to boiling; then the flame is removed and the flask sealed off. When water is poured over the flask, cooling it, the steam in the flask condenses reducing the vapor pressure, and the water boils at the lower temperature.
Smoke is drawn into a small chamber and examined under a microscope to observe Brownian motion.
Another demonstration for Brownian motion is an apparatus which gets placed on the overhead projector. Balls of different size can be used to show the random motion of molecules. As the speed on the agitator is turned up, the balls move faster.
Lastly, an ephysics applet [1] for Brownian motion is available on the web.
See Effects in a Vacuum [2]. Water boils at room temperature as the air above it is evacuated. Its temperature as measured by a thermometer drops rapidly. The more elaborate demonstration in which water is frozen in this way requires the addition of a beaker of concentrated sulfuric acid to the vacuum chamber to further reduce the vapor pressure.
A thermoelectric device which runs a propeller has two legs. The device will run if one leg is in a hot cup of water and the other in a cold cup of water, but not if both legs are in the same cup of water. (The hot and cold water can be mixed for the second step to show that the ability to do work has been lost.)
The "Thermobile" will spin (by shape-memory retention) if one end is dipped in hot water. Air at room temperature serves as the other reservoir (also see Laws of Thermodynamics [3]).
A spinner rolls indefinitely up and down a double ramp. Is this perpetual motion in violation of the First Law?
A Hilsch tube device connected to the room air source separates the air stream into hot and cold blowing streams. Does this violate the Second Law?
The "Thermobile" runs when dipped into hot water. Is this a heat engine with only one temperature reservoir?
The thermoelectric converter can also be run between ice water and liquid nitrogen demonstrating that there is still plenty of heat energy in ice water.
Professor Izzy Rudnick's 17-minute film on effects in liquid helium dramatically shows superfluity, fountains, super leaks, etc. and discusses the thermodynamic functions and properties of liquid helium.
A motor-driven molecular motion model which rattles various sized ball bearings around wildly fits on an overhead projector. The model also contains a somewhat larger object which is jiggled by impacts from the balls to demonstrate Brownian motion.
With this apparatus, a ball is bounced on air. From the period of oscillation the ratio Cp/Cv can be calculated. Instructions and method of calculation are available.
Links:
[1] http://ephysics.physics.ucla.edu/brownian-motion
[2] https://demoweb.physics.ucla.edu/node/304
[3] https://demoweb.physics.ucla.edu/node/336