Are the reactants and the products of a chemical reaction always going to have the same number of atoms? Why or why not?

Which of the following signs of a chemical reaction are observed in the reaction of potassium with water? precipitate formed temperature change smell produced gas produced color change

0.09 moles of sodium sulfate in 12 ml of solution

Which of the following is an indication that a substance has undergone a chemical change? a. no new product has been formed. b. the color of the substance has not changed. c. the original constitute has not changed. d. the molecular structure has changed.