Question: An experiment is performed to measure the mass percent of $CaCO_3$(s) in eggshells. Five different samples of $CaCO_3$(s) of known mass react with an excess of 2.0 M $HCl$(aq) in identical sealed, rigid reaction vessels. The pressure of the gas produced is measured with a pressure gauge attached to the reaction vessel. Since the reaction is exothermic, the reaction system is cooled to its original temperature before the pressure is recorded. The experimental data are used to create the calibration line below.  The experiment is repeated with an eggshell sample, and the experimental data are recorded in the table below. What following modifications will increase the rate of the reaction the most? Answer within in 2 words.
Answer: Using eggshells