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

Answer 1

To determine how the designs can be combined to best meet the criteria and constraints of a cold pack (minimum temperature, duration of coldness, and reusability), let's analyze the options based on the provided data.

1. Temperature Criteria: The ideal outcome is to have as cold a pack as possible.

   • Design 1 maintains temperatures of 4-6°C.
   • Design 2 maintains temperatures of 3-5°C.
   • Design 3 maintains temperatures of 5-7°C; this is the coldest overall.

2. Time Constraint: The pack should stay cold for about 5 minutes.

   • Design 1: stays cold for 5 minutes.
   • Design 2: stays cold for 3 minutes.
   • Design 3: stays cold for 7 minutes; this exceeds the target but is acceptable.

3. Reusability: It should be reusable if possible.

   • Design 1: reusable twice.
   • Design 2: reusable twice.
   • Design 3: reusable only once.

Now let's examine each option:

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

• Temperature: 4-6°C (Design 1) and Time: 7 minutes (Design 3). (Reusability is not mentioned; we do not combine reusability.)
• This option combines a good temperature with excellent time but lacks reusability.

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

• Reusability: twice (Design 2), Temperature: 5-7°C (Design 3).
• This option gives good temperature with decent reusability but poor staying time compared to Design 3.

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

• Temperature: 3-5°C (Design 2), Time: 5 minutes (Design 1).
• This option has a lower temperature and does not meet the coldest criteria.

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

• Reusability: once (Design 3), time: 3 minutes (Design 2).
• This option fails to fulfill both the time and reusability criteria effectively.

The best option based on the criteria and constraints would seem to blend the best qualities of each design, focusing on coldness and adequate time. Thus the best combinations focus would be:

The recommended outcome would be Design 3's temperature (5-7°C) and Design 1's time (5 minutes), though this is not an explicit option in the answers provided.

Assuming we're forced to choose from the provided options considering cold is the primary focus, A would be the closest option, gaining a compromise on coldness and time but lacking on reusability. So, the overall best option that still approaches the goals set out would be:

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