Question

When sugar dissolves in water in an open system, the mass is unchanged. When Alka-Seltzer is placed in water with a fizzing reaction in an open system, the mass becomes less. Explain how both can be correct, illustrating the Law of Conservation of Mass.

A) Sugar undergoes a physical change, while Alka-Seltzer undergoes a chemical change.
B) Sugar undergoes a chemical change, while Alka-Seltzer undergoes a physical change.
C) Sugar and Alka-Seltzer both undergo physical changes, but in different ways.
D) Sugar and Alka-Seltzer both undergo chemical changes, but in different ways.

Answer 1

The dissolution of sugar in water is a physical change, while the fizzing reaction of Alka-Seltzer in water is a chemical change, both of which can be explained using the Law of Conservation of Mass.

Step-by-step explanation:

The Law of Conservation of Mass states that matter is neither created nor destroyed during a chemical reaction. Both the dissolution of sugar in water and the fizzing reaction of Alka-Seltzer in water can be explained using this law.

When sugar dissolves in water, it undergoes a physical change. The sugar molecules separate and disperse throughout the water, but they are still sugar molecules. If the water is evaporated, the sugar will recrystallize and its mass will remain unchanged. This is an example of a physical change.

On the other hand, Alka-Seltzer undergoes a chemical change when it reacts with water. The reaction between the citric acid and sodium bicarbonate in the Alka-Seltzer tablet releases carbon dioxide gas. This gas bubbles out of the solution and escapes into the air. The loss of mass is due to the escape of the carbon dioxide gas, resulting in a decrease in the overall mass of the system. This is an example of a chemical change.