You have developed an understanding of the indicators of a chemical reaction. If you combined magnesium and hydrochloric acid (HCl) an exothermic reaction ( a reaction that gives off heat) will take place. What do you think will happen if you increase the concentration of the hydrochloric acid? Try adding 0.1M, 1M and 2M HCl to each piece of magnesium. How long does it take for the magnesium to dissolve? Maybe if you graph the data in a line graph you will see a trend.