Answer:
Chemical reaction
Explanation:
This process is called a chemical reaction. A chemical reaction is where atoms are rearranged to create various compounds, so the atoms can either be formed or broken.
For example, in this equation for the formation of water:
2H2(g) + O2(g) → 2H2O(l)
Here hydrogen and oxygen both combine to form water. This new compound, water, that has formed is what makes it a chemical reaction.
In this equation for the decomposition of calcium carbonate:
CaCO3(s) → CaO(s)+ CO2(g)
Here, CaCO3 has been broken down into CaO and CO2, which takes place as a chemical reaction.