A small balloon floats because it is lighter than air. We need to use a string to control it. Sometimes it is difficult to control because the wind can blow it away so easily. It is also easy for a small balloon to leak gas. It is obviously too small to carry any people. A hot air balloon, however, has different features from a small balloon. It is big enough to hold a heat source, and so can float high in the sky. A hot air balloon is easier to control than a small balloon because it's so big. Still, like a small balloon, a hot air balloon must follow the wind. Usually, because hot air balloons are so big, they can carry people up into the air!
来源：作文地带整理
