Here is a fun experiment to demonstrate vapor pressure. Take an empty two liter soda bottle. Fill it with one inch of water and a splash of rubbing alcohol. Next take about 1 ½ feet of ¼” plastic tubing and attach it to a flanged adapter that will fit a bike pump. Put a rubber cork into the bottle which has a ¼” diameter hole for the plastic tubing and insert tubing. Attach to the bike pump. Holding the cork securely in the bottle, pump 7 to 12 times. Release cork quickly being careful to aim away from people as some water may spray out. Hot air rushes out and cold air rushes in. A “cloud” or fog will instantly develop in the bottle.