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.