Question

In the lab, a student took a piece of aluminum foil weighing 0.50 g and ripped it into small pieces. They then took 5.00 g of copper chloride and crushed it in the mortar and pestle. After the copper chloride was crumbled it was dissolved in 100.0 mL of water in a beaker. The student weighed the substances in the beaker and found the mass to 205.00 g. The students then placed the aluminum foil pieces in the beaker and waited 2 minutes. The student noted that the beaker felt warmer than before they added the aluminum foil pieces. The student also noted that the pieces of aluminum foil turned an orangish color and they noted the presence of bubbles. The final mass of the reaction mixture was 201.00 g. Was the law of conservation of matter followed in this situation?

Why or why not?

Answer 1

The law of conservation of matter states that matter cannot be created or destroyed, but in an experiment with an open system where gas can escape, such as the observed reaction between aluminum and copper chloride, the mass can decrease due to the release of gas. If all products, including gases, were contained, the total mass would remain constant, in accordance with the law.

Step-by-step explanation:

The student observed that after adding aluminum foil to a copper chloride solution, the mass of the reaction mixture decreased from 205.00 g to 201.00 g. This may seem to suggest that the law of conservation of matter was not followed, as there is a loss of 4.00 g in mass after the reaction. However, the production of bubbles indicates that a gas was produced during the reaction, likely hydrogen from the reaction between aluminum and the acid in the copper chloride solution. This gas escaped from the mixture, which accounts for the loss in mass.

In a closed system, the law of conservation of matter states that matter cannot be created or destroyed. In this experiment, the system was not closed as gas escaped the beaker, hence the discrepancy in mass. If all matter could have been contained, including gases, the mass before and after the reaction would be equal, thereby following the law of conservation of matter.