Many people enjoy riding in hot air balloons. Some use them for romantic picnics and marriage proposals. Others race in competitions. Being above the earth gives a whole new perspective on the world around us. As the beginning of a hot air balloon ride, the balloon is flat because the pressure inside the balloon equals the pressure outside. When the air inside the balloon is heated, the speed of movement of those air molecules increases and the pressure goes up. After a while the balloon is completely expanded and the flight is ready to take off.
Matt couldn't take this heat any longer. It had been getting hotter and hotter all day. Matt looked outside at the thermometer, the mercury was definitely much higher than it had been this morning.
Where the mercury molecules spreading out or condensing?