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 1 and time Design 3 stays cold
B.
reusability of Design 3 and time Design 2 stays cold
C.
reusability of Design 2 and temperature maintained by Design 3
D.
temperature maintained by Design 2 and time Design 1 stays cold

Answer 1

To determine which combination of designs best meets the criteria and constraints, we need to focus on the three key requirements: the coldness of the temperature maintained, the duration it stays cold, and the reusability.

1. Temperature Desired: As cold as possible.
2. Time Requirement: Should stay cold for about 5 minutes.
3. Reusability: Should be reusable.

Analyzing the designs:

• Design 1: Maintains a temperature of 4-6°C and stays cold for 5 minutes, reusable twice.
• Design 2: Maintains a temperature of 3-5°C and stays cold for 3 minutes, reusable twice.
• Design 3: Maintains a temperature of 5-7°C and stays cold for 7 minutes, reusable once.

Now, let's evaluate the options provided:

A. Temperature maintained by Design 1 and time Design 3 stays cold:

• Temperature: 4-6°C (Design 1)
• Time: 7 minutes (Design 3)
• Reusability: Not mentioned (Design 3 is once)

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

• Reusability: Once (Design 3)
• Time: 3 minutes (Design 2)
• Temperature: Not mentioned (but would be 3-5°C, which is lower)

C. Reusability of Design 2 and temperature maintained by Design 3:

• Reusability: Twice (Design 2)
• Temperature: 5-7°C (Design 3)
• Time: Not mentioned

D. Temperature maintained by Design 2 and time Design 1 stays cold:

• Temperature: 3-5°C (Design 2)
• Time: 5 minutes (Design 1)
• Reusability: Not mentioned

Considering the requirement of maintaining the lowest temperature possible while meeting the time constraint of staying cold for about 5 minutes, Option A seems the most appealing, as it offers the best combination of temperature (4-6°C from Design 1) and a longer time (7 minutes from Design 3), although it sacrifices reusability.

Thus, the best combined approach to meet the criteria and constraints would be:

A. temperature maintained by Design 1 and time Design 3 stays cold.

This combination prioritizes maintaining a colder temperature and maximizes the time the pack remains cold, even though it does not consider reusability.