THe challenge
Create an effective, safe and low cost hand warmer to keep san marin sports fans hands warm in the winter
Investigating the prototype
To come up with the final prototype we went through these design changes and questions.
-Where to put the water?
-Where to put the calcium chloride?
-How many bags we should use?
-What size the hand warmer should be?
-How much of each substance we use?
-How to keep the salt and water separate/how to pop the bags when needed?
-Where to put the water?
-Where to put the calcium chloride?
-How many bags we should use?
-What size the hand warmer should be?
-How much of each substance we use?
-How to keep the salt and water separate/how to pop the bags when needed?
chemical testing calulations
These are the calculations we did with the salt and the water before we started making prototypes.
hand warmer
Here is a basic outline of our hand warmer and what it is made up of.
Our model contains 3 bags
-The first bag contains 25 mL of water
-The bag of water is then placed inside another bag that contains 10 g of CaCl2
-Then a final bag is placed around the water and CaCl2
-Ziploc bags
-25ml of distilled water
-10g of calcium chloride
Our model contains 3 bags
-The first bag contains 25 mL of water
-The bag of water is then placed inside another bag that contains 10 g of CaCl2
-Then a final bag is placed around the water and CaCl2
-Ziploc bags
-25ml of distilled water
-10g of calcium chloride
Data
This is the data we collected once we made a sealed prototype.
Trial 1:
-5 grams CaCl2 and 50 mL water
-Stayed warm for one minute 15 seconds
Trial 2:
-30 grams CaCl2 and 10 mL water
-Stayed warm for 45 seconds
Trial 3:
-10 grams CaCl2 and 25 mL water
-Stayed warm for 2 minutes 30 seconds
Trial 1:
-5 grams CaCl2 and 50 mL water
-Stayed warm for one minute 15 seconds
Trial 2:
-30 grams CaCl2 and 10 mL water
-Stayed warm for 45 seconds
Trial 3:
-10 grams CaCl2 and 25 mL water
-Stayed warm for 2 minutes 30 seconds
How to operate
1.The water is sealed in the first bag with a little air in it.
2.The water bag then goes into the bag containing the calcium chloride with no air.
3.These bags are then put into another bag.
4.When the two inner bags are popped, the calcium chloride and water mix together. When the ionic solid dissolves, the cations and anions in the ionic solid and hydrogen molecules in the water are broken. New bonds between water molecules, cations, and anions are formed. More energy is required to break these bonds than is released, and the overall process absorbs energy as heat.
2.The water bag then goes into the bag containing the calcium chloride with no air.
3.These bags are then put into another bag.
4.When the two inner bags are popped, the calcium chloride and water mix together. When the ionic solid dissolves, the cations and anions in the ionic solid and hydrogen molecules in the water are broken. New bonds between water molecules, cations, and anions are formed. More energy is required to break these bonds than is released, and the overall process absorbs energy as heat.
Cost analysis
This is our cost analysis for 100 protoype hand warmers.
Cost of calcium chloride: $5.90 for 500g(2)
-Cost of Ziploc snack bags: $8(2)
-Cost of water: $0.06 (250mL)
-Total cost: $ 0.21 for one, $21 for 100
-Selling price $1 per handwarmer
Cost of calcium chloride: $5.90 for 500g(2)
-Cost of Ziploc snack bags: $8(2)
-Cost of water: $0.06 (250mL)
-Total cost: $ 0.21 for one, $21 for 100
-Selling price $1 per handwarmer
Marketing
We plan on taking the following steps to ensure our hand warmer is a worthwhile investment.
-Print out flyers
-Have morning announcements advertise our handwarmers
-Have coaches inform players and there families about them
-Print out flyers
-Have morning announcements advertise our handwarmers
-Have coaches inform players and there families about them
Why is this project important?
-Helped us learn about endothermic and exothermic reactions
-Improves our problems solving skills when it comes to the product design process
- Allows STEM Marin students to actively help solve real problems in the community
-Raises school spirit (and money!) at sports events
-Improves our problems solving skills when it comes to the product design process
- Allows STEM Marin students to actively help solve real problems in the community
-Raises school spirit (and money!) at sports events