Jen and Ori are conducting an experiment to observe how sand and water absorb energy. They obtain two identical 1000-milliliter (mL) beakers, add 500 mL of distilled water to the first beaker, and 500 cubic centimeters (cm 3 ) of sand to the second beaker. They place both beakers on a hot plate that is set to medium heat. Thermometers are placed in each beaker and held with clamps. Both beakers are heated for seven minutes and then removed from the hotplate and cooled for an additional fifteen minutes. Jen and Ori record the temperature of each beaker at one-minute intervals. How could Jen and Ori have increased the reliability of their experiment?