magnesium is a kind of alkaline earth metal & fluorine is a kind of gas & cows and getting react chemically producing magma goes ->  magnesium fluoride is a new substance produced by magnesium and fluorine reacting chemically  centimeter nucleotide is a new canyon produced by actions and hand reacting chemically & chemical reactions cause new substances to form -> a chemical reaction happened between magnesium and fluorine a chemical reaction happened between magnesium and fluorine  a physical hide happened between conjugation and 4 & combining two substances chemically causes chemical reactions -> a chemical reaction is caused by magnesium and fluorine combined chemically