Designing a Hand Warmer
Sinead Maharrey and Malik Shalash
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.
The Experiment
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
Procedure
Part 1: Heat capacirt of the calorimeter
- Set up a calorimeter using two cups
- Measure 100 mL of distilled water into the calorimeter
- Use a temperature probe to measure and record the initial temperature of the water
- Heat 125 mL of distilled water to between 50 and 60 degrees C
- Immediately transfer it into the room temperature water in the calorimeter
- Record the mixing temperature after 20 seconds
- Calculate the calorimeter constant
Part 2: Calorimetry procedure
- Measure 100 mL of distilled water into the calorimeter
- Measure and record the initial temperature
- Measure 5 grams of anhydrous magnesium sulfate into a weigh boat
- Slowly add it into the water in the calorimeter
- Insert a temperature probe and measure and record the highest temperature the mixture reaches
- Use the data to calculate the molar heat of solution for magnesium sulfate
Part 3: Research and design a hand warmer
- Repeat the steps in part 2 for sodium chloride, lithium chloride, and sodium carbonate
- Record the initial and final temperatures for each reaction
- Calculate the heat of solution for each solid
- 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
- Place 10 grams of the chosen solid into a large Ziploc bag
- Place 40 mL of distilled water into a large Ziploc bag
- Release the water into the outer bag, allowing the reaction to take place
- Record the initial and final temperature of the hand warmer
Procedure Gallery
We connected a temperature probe to the computer in order to monitor the temperature changes occurring during the reactions.
This is our final hand warmer design... 10 g of sodium carbonate in an outer bag with 40 mL of distilled water in an inner bag. When the inner bag is broke, the water mixes with the solid and the bag warms up.
We carefully measured 5 grams of each ionic solid to add to the reaction.
We added 100 mL of water to the calorimeter for each reaction.
We used a program called Logger Pro and a temperature probe to monitor the temperature of the reaction.
We used a program called Logger Pro and a temperature probe to monitor the temperature of the reaction.
Calculations
Part 1: Calorimeter constant
Part 2: Molar heat of solution for magnesium sulfate
Part 3: Molar heat of solution for test chemicals
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.