In this demonstration, we will be concerned with temperature and air pressure. When air is heated, the atoms and molecules begin to move faster in different directions. As this heated air becomes more spread out, it becomes lighter than the surrounding cooler air. Cooler, dense air moves underneath the warmer, lighter air. When this happens, the warmer air begins to rise.
Warmer air has less pressure than cooler air.
The equator receives direct rays from the sun and is much warmer than the earth's poles that receive indirect rays. The earth is heated unevenly from the sun. This uneven heating creates areas of low pressure at the equator and areas of high pressure at the poles. As we will see later, this factor helps create much of our weather. The demonstration below is a simple way of observing the affects of air as it is being heated.