Question

1. a process in which one or more substances are changed into others is called: physical change, chemical reaction, conservation of mass, coefficient

Explanation:

A chemical reaction is a process where one or more substances are transformed into other substances. A physical change only affects the physical properties like state, shape etc. without changing the chemical composition. Conservation of mass is a principle, not a process of changing substances. A coefficient is a number in a chemical - equation related to the amount of substances in a reaction, not the name of the process of changing substances.

Answer:

C. chemical reaction