Can somebody plz help me with some grade7science?

List four observations that indicate that a chemical reaction may be taking place

The chemical equation below shows the reaction of sodium (na) and chlorine (cl) to form sodium chloride (nacl). 2na + cl2 → 2nacl in this equation, which of the following is a reactant? i. sodium ii. chlorine iii. sodium chloride

In a ball-and-stick molecular model, what do the sticks represent?