Continue adding salt until the glass overflows. Then measure the salt that is left in the shaker and determine how much was added before the water overflowed. Do the same thing with rubbing alcohol in the other glass. Be sure to measure the amount added. The molecules of salt and alcohol apparently fit between the water molecules without increasing volume until the spaces are filled.
Students love to boil water with an ice cube.
You will need a Pyrex test tube and stopper. Put about an inch of water in the bottom of the tube, heat it to boiling, remove it from the heat to stop the boiling action, and tightly stopper the tube. Turn the tube upside down and apply an ice cube or cold cloth to the tube. The water will begin boiling again. The cold lowers the pressure of the air above the water, which changes the vapor to liquid.