A chemical change is different than a physical change because in a chemical change Chemicals are used

Molecules do not physically touch

A new substance is formed and in a physical change no new substance is formed

The change can be seen but in a physical change it cannot

answer; i believe that the correct answer is (light);

the nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and dna, the building blocks of all life. plants absorb nitrogen in the form of ammonium, nitrate ion and, on rare occasions, as amino acids. animals receive nitrogen necessary for biological processes from feeding on living or dead organic matter.