CONNEXUS alternate test?

A student claims that mass is not conserved in chemical reactions and uses a reaction in which they measure the mass of liquid alcohol then light it on fire, measuring the mass of the liquid (water) remaining in the dish after the fire burns out. The mass of the liquid after the reaction is less than the mass of the alcohol before the reaction. Is this valid evidence of the student's claim? Why or why not?*

-Yes, it supports the claim because the masses were not the same and were measured carefully

-No, it does not support the claim because it is not a closed system.

-Yes, it supports the claim because the student completed an experiment to prove their
claim.

-No, there was not a chemical reaction.

No, it does not support the claim because it is not a closed system

To determine the validity of the student's claim, we need to understand the concept of mass conservation in chemical reactions. Mass conservation states that in a closed system, the total mass before a chemical reaction is equal to the total mass after the reaction.

To approach this question, we can use our knowledge of mass conservation and analyze the scenario presented by the student:

1. The student measures the mass of liquid alcohol before the reaction.
2. They light the alcohol on fire and measure the mass of the liquid (water) remaining after the fire burns out.

Now, let's evaluate the answer choices provided:

- "Yes, it supports the claim because the masses were not the same and were measured carefully."

This statement is incorrect. While it is true that the masses were measured carefully and were not the same, it does not automatically support the claim of mass not being conserved. Mass conservation in chemical reactions applies to closed systems, but the scenario does not provide information about whether it was a closed or open system.

- "No, it does not support the claim because it is not a closed system."

This statement is correct. The key term here is a closed system. To determine whether mass is conserved, the system in which the reaction occurs must be closed, meaning no mass can be added or lost from outside the system during the reaction. If the dish in which the reaction took place was open, it is possible that some mass was lost through evaporation or other factors, resulting in the observed decrease in mass. Therefore, this scenario does not provide valid evidence to support the claim.

- "Yes, it supports the claim because the student completed an experiment to prove their claim."

This statement is incorrect. Merely completing an experiment does not automatically support the claim. The experiment needs to be conducted under appropriate conditions, including a closed system as mentioned earlier.

- "No, there was not a chemical reaction."

This statement is incorrect as it disregards the scenario described by the student, in which a chemical reaction occurred between the alcohol and oxygen resulting in the formation of water.

In conclusion, the correct answer is "No, it does not support the claim because it is not a closed system." The scenario provided lacks information about whether the system was closed or open, making it impossible to determine whether the mass decrease was due to a violation of mass conservation or external factors.

The correct answer is:

No, it does not support the claim because it is not a closed system.

Explanation: Mass is always conserved in a closed system, where no mass can enter or leave during a chemical reaction. In the scenario described, the system is not closed because the liquid alcohol is being burned and converted into gas, which can escape from the dish. The loss of mass observed is likely due to the evaporation of the alcohol, not the violation of mass conservation. Therefore, this experiment does not provide valid evidence to support the student's claim that mass is not conserved in chemical reactions.