What are the substances that are present before a reaction takes place called the ones to the left of the arrow?; What is the reaction of a substance with oxygen called?; What are molecules called before and after a chemical reaction?

A mechanism that significantly directs the chemical transformation of one group of chemical substances or molecules into another may be referred to as a chemical reaction. Numerous catalysts are used in this chemical transformation process to speed up the reaction.

Reactants are the elements to the left of the arrow in a chemical equation. Reactants are substances that are present at the beginning of a chemical reaction. Products are the substance(s) to the right of the arrow.
When a chemical combines with oxygen gas, it produces a combustion reaction that releases energy in the form of heat and light. O2 must be one of the reactants in combustion processes. Hydrogen gas is burnt to produce water vapor.

[tex]2H2(g)+O2(g)[/tex] → [tex]2H2O(g)[/tex]

Therefore, the reaction of a substance with oxygen called combustion.

3. We refer to the molecules before and after a chemical reaction, respectively, as reactants and products.

To learn more about Chemical reaction from the given link.

https://brainly.com/question/11231920

#SPJ4