# Designing a Hand Warmer

## Objective

Hand Warmers are used to quickly to provide warmth to your fingers when it is cold by using chemical reactions that release heat. They usually consist of an outer package contain a chemical reactant and then an inner pouch filled with water. When the pouch is activated, the chemical dissolves in the water and creates a chemical reaction that releases heat. In this lab we were tasked with researching various reactants to find which ones safely produced the most heat at an efficient cost. We then had to construct a hand warmer using our chosen reactant.

## Materials

• Two ziploc bags
• 15 grams of Na2CO3
• 5 grams of Anhydrous Magnesium sulfate
• 5 grams of NaCl
• 5 grams of LiCl
• Distilled Water
• Temperature Probe
• Calorimeter

## Part 1: Heat capacirt of the calorimeter

1. Set up a calorimeter using two cups
2. Measure 100 mL of distilled water into the calorimeter
3. Use a temperature probe to measure and record the initial temperature of the water
4. Heat 125 mL of distilled water to between 50 and 60 degrees C
5. Immediately transfer it into the room temperature water in the calorimeter
6. Record the mixing temperature after 20 seconds
7. Calculate the calorimeter constant

## Part 2: Calorimetry procedure

1. Measure 100 mL of distilled water into the calorimeter
2. Measure and record the initial temperature
3. Measure 5 grams of anhydrous magnesium sulfate into a weigh boat
4. Slowly add it into the water in the calorimeter
5. Insert a temperature probe and measure and record the highest temperature the mixture reaches
6. Use the data to calculate the molar heat of solution for magnesium sulfate

## Part 3: Research and design a hand warmer

1. Repeat the steps in part 2 for sodium chloride, lithium chloride, and sodium carbonate
2. Record the initial and final temperatures for each reaction
3. Calculate the heat of solution for each solid
4. Use the data calculated and the information provided about the cost of the solids, determine which reactant would be the most effective for use in a hand warmer

## Part 4: Design a hand warmer

1. Place 10 grams of the chosen solid into a large Ziploc bag
2. Place 40 mL of distilled water into a large Ziploc bag
3. Release the water into the outer bag, allowing the reaction to take place
4. Record the initial and final temperature of the hand warmer

## Part 4: Molar heat of solution for our hand warmer

We chose to use sodium carbonate for our hand warmer design.

## Conclusion

The chemical we chose was sodium carbonate. When we tested the temperature change of different reactants, lithium chloride experienced the highest temperature increase. Sodium carbonate expirienced a slightly lower change but the cost of this chemical is significantly lower than that of lithium chloride.