What is free nitrogen?
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nitrogen that is ready for plants to use
nitrogen that has been fixed by bacteria
nitrogen that cannot be used by organisms
nitrogen that is returned to the soil by decomposers

Match each description with the correct form of energy. 1. energy of an object's position above the ground. 2. stored in the bonds of atoms and molecules 3. stored in the nucleus of an atom 4. energy of vibrating molecules 5. movement of objects used to do work 6. created by vibrations in electric and magnetic fields chemical energy mechanical energy heat gravitational energy light nuclear energy