If it takes more energy to break the original bonds than is released when the new bonds are formed, then the net energy of the reaction is negative. This means that energy must be pumped into the system to keep the reaction going. Such reactions are known as endothermic.
A cloud that forms on the ground is called fog. Some clouds you see in the sky might be from airplanes. These are called contrails. High level cirrus clouds may travel at speeds up to 100 mph.
