Cold Pack Investigation

Question

Cold Pack Investigation
People use self-warming and self-cooling devices for many purposes such as keeping drinks cold or food warm. Medical professionals also use these types of devices to store medicines and other substances that need to stay colder than room temperature. These cooling and warming devices use a chemical reaction to produce their chilling and warming effects. Compounds combine in endothermic (heat absorbing) or exothermic (heat releasing) reactions within these devices to help them keep items cool or warm.

Jacob and Natalie are asked by their science teacher to design a warming or cooling device. They decide to design a cold pack that can be used to help keep food cool. Jacob and Natalie read about different substances that can be used inside cold packs and learn that most cold packs use endothermic reactions to cool objects. They find the table below while researching.

The table titled 'Effect on Temperature of Different Substances' shows Sample, Composition, Initial temperature in degrees Celsius and Final temperature in degrees Celsius. Sample 1's composition is Ammonium nitrate, urea and water, Initial temperature is 22.0, and final temperature is negative 17.5. Sample 2's composition is Ammonium nitrate and water, Initial temperature is 22.0, and final temperature is negative 4.0. Sample 3's composition is Urea and water, Initial temperature is 22.0, and final temperature is 4.0. Sample 4's composition is Water, initial temperature is 22.0, and final temperature is 22.0

Multiple Choice Question
Which sample uses the substance(s) that Jacob and Natalie should use to make a cold pack that will do the best job of keeping food cool?

A.
Sample 1, because it absorbs the most energy

B.
Sample 2, because it absorbs the most energy

C.
Sample 3, because it absorbs the least energy

D.
Sample 4, because it absorbs the least energy

Answer 1

To determine which sample would be best for creating a cold pack, we need to look at the temperature changes for each sample.

1. Sample 1: Initial temperature: 22.0°C, Final temperature: -17.5°C
   Temperature change = 22.0 - (-17.5) = 39.5°C

2. Sample 2: Initial temperature: 22.0°C, Final temperature: -4.0°C
   Temperature change = 22.0 - (-4.0) = 26.0°C

3. Sample 3: Initial temperature: 22.0°C, Final temperature: 4.0°C
   Temperature change = 22.0 - 4.0 = 18.0°C

4. Sample 4: Initial temperature: 22.0°C, Final temperature: 22.0°C
   Temperature change = 22.0 - 22.0 = 0.0°C

The sample that results in the largest temperature drop indicates the highest energy absorption (endothermic reaction), making it the most effective for cooling.

• Sample 1 has the largest temperature decrease of 39.5°C.
• Sample 2 has a decrease of 26.0°C.
• Sample 3 has a decrease of 18.0°C.
• Sample 4 has no decrease in temperature at all.

Based on the temperature changes, Sample 1 absorbs the most energy and therefore will do the best job of keeping food cool.

The correct answer is: A. Sample 1, because it absorbs the most energy.