A teacher asked her students to design a cold pack. The desired criteria and constraints for the cold pack are as follows:

Question

it should be as cold as possible
it should stay cold for about 5 minutes
it should be reusable
The students were instructed to mix ammonium nitrate crystals in plastic bags filled with water. They were split into three groups, and each group created a design. Each design used a different amount of ammonium nitrate crystals. The table shows the cold pack designs created by the three groups.

Temperature Maintained (°C) Amount of Time it Stays Cold (minutes) Reusability
Design 1 4-6 5 twice
Design 2 3-5 3 twice
Design 3 5-7 7 once

How could the designs be combined to best meet the criteria and constraints?
A.
temperature maintained by Design 2 and time Design 1 stays cold
B.
reusability of Design 3 and time Design 2 stays cold
C.
temperature maintained by Design 1 and time Design 3 stays cold
D.
reusability of Design 2 and temperature maintained by Design 3

Answer 1

To determine how the designs could be combined to best meet the criteria and constraints for the cold pack, we need to look at each option presented in relation to the original requirements: it should be as cold as possible, stay cold for about 5 minutes, and be reusable.

Let’s analyze the options:

A. Temperature maintained by Design 2 and time Design 1 stays cold

• Temperature: 3-5 °C (Design 2, not as cold as possible)
• Time: 5 minutes (Design 1, meets the requirement)
• Reusability: twice (Design 1, reusable)
• Overall, this design does not meet the coldest requirement.

B. Reusability of Design 3 and time Design 2 stays cold

• Reusability: once (Design 3, not reusable)
• Time: 3 minutes (Design 2)
• Overall, this design does not meet the reusability criterion.

C. Temperature maintained by Design 1 and time Design 3 stays cold

• Temperature: 4-6 °C (Design 1, maintains a moderate coldness)
• Time: 7 minutes (Design 3, exceeds the requirement)
• Reusability: twice (Design 1, reusable)
• This design keeps a reasonable cold temperature and stays cold longer than required.

D. Reusability of Design 2 and temperature maintained by Design 3

• Reusability: twice (Design 2, reusable)
• Temperature: 5-7 °C (Design 3, maintains a colder temperature)
• Overall, this design meets the temperature requirement but lacks clarity on how reusability from Design 2 affects Design 3.

Combining the strengths of the designs while ensuring the requirements and constraints are satisfied, Option C stands out as the best choice. It provides a good balance of a suitable cold temperature, extends the time the pack stays cold beyond the requirement, and maintains the reusability aspect.

Therefore, the best combination would be:
C. temperature maintained by Design 1 and time Design 3 stays cold.