Making a hot pack with calcium chloride involves a simple chemical reaction that releases heat. Here's how you can do it:
Materials You'll Need:
- Ziplock bag (heavy-duty recommended)
- Super Absorbent Polymer (SAP) crystals (the stuff inside diapers works well, or you can buy them online. This helps prevent leaks.)
- Calcium chloride (available at hardware stores as a de-icer)
- Water
- Measuring cup
Steps:
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Prepare the SAP: Open the ziplock bag and place the SAP crystals inside.
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Hydrate the SAP: Add about 1/4 cup of water to the bag.
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Allow Absorption: Seal the bag tightly and let it sit for several minutes. The SAP crystals will absorb most of the water, forming a gel. This step helps contain the liquids and prevent leaks from your hot pack.
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Add the Calcium Chloride: Add the calcium chloride to the bag on top of the gel. The amount depends on the desired heat and size of the bag, but start with a small amount, about 1/4 cup.
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Initiate the Reaction: Add another 1/4 cup of water.
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Seal and Mix: Securely seal the ziplock bag, making sure to remove as much air as possible. Gently mix the contents by squeezing and manipulating the bag.
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Observe: The bag will begin to warm up as the calcium chloride dissolves in the water. This is an exothermic reaction, meaning it releases heat.
Important Safety Considerations:
- Secure Seal: Ensure the ziplock bag is sealed tightly to prevent leaks. Calcium chloride can irritate the skin.
- Double Bag (Optional): Consider placing the first bag inside a second ziplock bag for extra protection against leaks.
- Supervision: This experiment should be conducted under adult supervision, especially if children are involved.
- Disposal: Once the hot pack has cooled, dispose of it properly. Do NOT ingest the contents. Check local regulations for proper disposal of calcium chloride solutions.
- Skin Contact: If the solution leaks and comes into contact with skin, wash the affected area thoroughly with soap and water.
- Eye Contact: If the solution gets in your eyes, rinse them immediately with plenty of water and seek medical attention.
Why This Works:
Calcium chloride dissolves in water in an exothermic reaction, meaning that heat is released. The SAP crystals absorb the initial amount of water to create a gel, which helps to keep the calcium chloride and water in contact with each other, while also preventing leaks.
