Thermal Energy

Question

A student plans to conduct an experiment using foam cups, some water, a rock, and a piece of metal.

At first, the rock is placed on a scale, and its mass of 123 grams gets recorded. Then, 123 grams of water get heated on the stove to 100°C. The water is poured into a foam cup, followed by the unheated rock. The temperature of the water is recorded with a thermometer until the temperature appears to stabilize.

In the second part of the experiment, water gets heated on the stove. The water gets poured into a foam cup, and then a piece of metal is added. The temperature of the water is recorded with a thermometer until the temperature appears to stabilize.

The student plans to compare the results from each part of the investigation.

Multiple Choice Question
What is the best way to measure the mass of the boiling water in the first part of the experiment?

A.
From left to right, the illustration shows to measure the mass of the cup with the rock on the scale and then add hot water to the cup until the scale shows the total mass of the cup and the rock plus 123 additional grams of water. The left scale has an empty cup with a rock inside and reads 126.5 grams. The right scale has the cup with the rock and is filled with water; it reads 249.5 grams.

B.
From left to right, the illustration shows to measure the mass of the cup on the scale and then add hot water to the cup until the scale shows the total mass of the cup plus 123 additional grams of water. The left scale has an empty cup and reads 3.5 grams. The right scale has a cup filled with water and reads 126.5 grams.

C.
From left to right, the illustration shows to measure the mass of the cup on the scale and then add hot water to the cup until the scale shows that the total mass for the cup and water together is 123 grams. The left scale has an empty cup and reads 3.5 grams. The right scale has a cup filled with water and reads 123 grams.

D.
From left to right, the illustration shows to measure the mass of the cup on the scale and then put the rock in the cup and add hot water to the cup until the scale shows that the total mass for the cup, water, and rock together is 123 grams. The left scale has an empty cup and reads 3.5 grams. The right scale has the cup with the rock filled with water and reads 123 grams.

Answer 1

To measure the mass of the boiling water in the first part of the experiment accurately, you would want to ensure that you include the mass of both the foam cup and the rock when determining the amount of water to add.

This means that your measurement should reflect the total mass of the cup and the rock plus the water you need to reach a specific desired total mass.

Given the options:

• Option A: This option does not clearly state how to measure the mass of just the water separately, and it seems to misinterpret the mass being measured by suggesting a total mass that includes the rock.
• Option B: This option states to measure the cup first and add water to reach a total of 126.5 grams, which is incorrect, as you do not account for the rock's mass separately in this measurement.
• Option C: This suggests measuring to a total of 123 grams, which doesn't account for the mass of the rock correctly.
• Option D: This option also suggests measuring in a way that does not make sense for the total mass needed.

The best process here would involve first weighing the empty cup and then adding the rock and ensuring the total mass when combined with water reaches the combined mass of the rock and water—while also accurately reflecting the 123 grams of rock's mass, which none of the options do precisely.

After careful consideration, Option A could be interpreted to have a reasonable framework since it mentions the total mass including the rock plus the desired water mass, though the water mass addition part could seem vague. However, this reflects the closest understanding to find the correct mass for the boiling water while ensuring it encompasses the already measured rock.

Ultimately, the options are somewhat incorrect because they all need to clarify how to balance the mass correctly. But the general idea is to include the rock's mass in the total combined mass.

In context, I would recommend selecting Option A as the most logical approach given the choices presented, but point out that precision in instructions could still be improved.