Reusable heat pack how does it work

This is exactly the phenomenon which is applied in the working of sodium acetate heat packs to produce heat. The special ingredient within these heating pads is sodium acetate. When it is mixed with water and a stainless steel disc you have the perfect solution for instant, safe and a reusable form of heat. When the disc of the heat pad is clicked, it pushes the liquid through the disc which immediately begins the process of changing the temperature of the liquid while keeping it in a liquid state.

The temperature, as a result, rises up to degrees Fahrenheit. The amount of liquid inside the heat pad determines the amount of time the heat pad remains hot until it eventually cools into a hardened state. Is this safe? Yes, sodium acetate is the sodium salt of acetic acid. It's also the primary flavoring in many edible items such as potato chips and considered a food grade product and can be a common additive. When the salt is dissolved in water, the ionic bonds of the salt separate.

This process requires energy, which is obtained from the surroundings. The ions then form bonds with the water, a process that releases energy. If more energy is released than taken in, then the process is exothermic, making the solution feel warmer. If more energy is taken in than released, then the process is endothermic, making the solution feel cooler. Commercially, there are 2 other commonly sold types of instant hot packs.

One heats up when exposed to air. This hot pack functions as iron reacts with oxygen to form iron III oxide, an exothermic reaction. The other type relies on the super cooling of sodium acetate. Upon heating the solution, it can become supersaturated. Without a seed crystal, the sodium acetate will remain in solution as it cools.

This type of hot pack typically contains a metal disk that provides a site for crystallization when depressed. As the sodium acetate forms a regular crystal arrangement, heat is released. This hot pack is reusable as it can be regenerated in boiling water to once again form the supersaturated solution. Use this activity only in accordance with established laboratory safety practices, including appropriate personal protective equipment PPE such as gloves, chemical splash goggles, and lab coats or aprons.

Ensure that students understand and adhere to these practices. Know and follow all federal, state, and local regulations as well as school district guidelines for the disposal of laboratory wastes.

Students should not eat, drink, or chew gum in the lab and should wash their hands before and after entering or exiting the lab. Design a portable, 1-time-use hot pack or cold pack for treating injuries. The pack must have g of water separated from a solid chemical and be activated only when the user does something to the pack to mix the 2 components.

The following is a guide for creating your thermal pack. Ensure that you understand how your teacher expects you to present your designs. We use cookies to provide you with a great user experience. By using our site, you accept our use of cookies. You can review our cookie and privacy policy here.

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Product Support You have questions-we have answers. View all Product Support. What if you could somehow supercool the water? That is, say that you could get the water's temperature to 10 degrees below the freezing point without it crystallizing into a solid -- you can sometimes do this using a very clean glass and distilled water so there are no points for the water to begin crystallizing.

In this condition, if you tap the glass the temperature of the water will jump up to 32 degrees F 0 degrees C , and the water will solidify quickly.

A heat pack like the one you are describing contains sodium acetate and water. It turns out that sodium acetate is very good at supercooling.

It "freezes" at degrees F 54 degrees C , but it is happy to exist as a liquid at a much lower temperature and is extremely stable. Clicking the disk, however, has the ability to force a few molecules to flip to the solid state, and the rest of the liquid then rushes to solidify as well.

The temperature of the solidifying liquid jumps up to degrees F in the process. When you boil the solid, you melt it back to the liquid state. You have to completely melt every crystal, by the way, or the liquid will quickly re-solidify.

You can repeat this cycle forever, theoretically, just as you can freeze and melt water as many times as you like. The plastic pouch eventually wears out and leaks, though since sodium acetate is a food additive, it is non-toxic.

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