Science Buddies: "Ask an Expert"

I'm very sorry for the urgency here but I am stumped on what my results mean from my experiment. I changed the starting temperature for each hand warmer before starting each reaction to 0 degrees Celsius, 10, 20, 30, and 40. My infrared thermometer that I used to take the temperature seems very inaccurate and this may be why I'm having trouble coming to a conclusion but I would like to know what I should have been able to conclude from my results. What I gathered was that the max temperature was highest for the 40 degree Celsius hand warmer, and the 10 degree Celsius sample lost heat the fastest. Crystals also were much longer on the 40 degree sample and there were less of them. What confused me was that the middle temperature (20 degrees) retained heat the longest and its max temperature was very close to all the other samples. Is there supposed to be a significant difference in the rates of heat loss for each starting temperature and is the max temperature supposed to be highest for colder or hotter starting temperatures? I would try to find new ways to test this myself but the report is due tomorrow and I can't find anything about what changing the starting temperature would do to the reaction.
Thank you so much,
Zack

Hi Zack,

I'm assuming that you are working on the project described here:

https://www.sciencebuddies.org/science- ... rk#summary

As mentioned in the project background, the sodium acetate hand warmer can reach a maximum temperature of 58 degrees C. This is the temperature at which sodium acetate trihydrate loses water of hydration and begins to dissolve. And it represents the maximum heating possible from the crystallization process. The maximum temperature is 58 degrees regardless of the starting temperature.

Heat loss from the hand warmer will be influenced by the mass of crystals formed, and the heat conducted away from the hand warmer through contact with surfaces. More crystal mass and faster heat loss is expected at lower starting temperatures.

I hope this helps. Please ask again if you have more questions.

A. Norman