When a piece of copper metal is heated in air, it joins together with oxygen in the air (a chemical reaction). Then if the copper is weighed, it is found to have a greater mass than the original piece of metal. If the air was then measured with very specialized instruments, what can you expect the mass of the air to be? A. the same as before the chemical reaction B. more than before the chemical reaction C. twice as much as before the chemical reaction D. less than before the chemical reaction