Introduction:
Challenge: Create an effective, safe, and low cost hand warmer to keep San Marin sports fans warm during the winter months
Investigate:
Investigate:
- Where to put each needed substance
- How many bags we need
- How much of each substance we need
- Our model had 3 bags
- The first bag contained 25 mL of water
- That bag is then placed inside another bag that contained 10 g of CaCl2
- Then another bag is placed around the other two bags just to keep it sealed
Trials:
- 5g of CaCl2 and 50mL of water, this mixture stayed warm for 1 minute 15 sec
- 30g of CaCl2 and 10 mL of water, this mixture stayed warm for 45 sec
- 10g of CaCl2 and 25 mL of water, this mixture stayed warm for 2 minutes 30 sec (This was our most successful trial)
- Calcium chloride is $5.90/ 500g
- Ziploc bags are $8 per box
- Total: $21 for 100 warmers
Slideshow:
Reflection:
This was a very fun hands on project. We got to apply concepts we had been learning in class to a project, such as the principles of exothermic and endothermic reactions. After all of the students have presented their hand warmers, the best hand warmer will be picked and used to sell at San Marin sporting events. I liked how we got to work towards something that would be used in real life instead of just a hypothetical thing. I was surprised that just one substance with water could create heat for so long.