Citric Acid and Baking Soda Cold Pack

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kimmy
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Joined: 01 Jun 2006, 10:00
Job Title: School Lab Assistant
School: Quirindi High School
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State/Location: NSW

Citric Acid and Baking Soda Cold Pack

Post by kimmy » 05 Sep 2019, 14:18

If you are after a cheap and quick experiment to show endothermic chemical reaction than this one is for you.
It is quick and cheap what more can we ask for.
I did this in a beaker with thermometer so the students would be able to see the temperature drop.
It did fizz up heaps so use a 400ml beaker at least.
I used 1 tablespoon of each and just a slurp of water (sorry did not measure). 8-)

The key advantages of using citric acid and baking soda are that the two chemicals are non-toxic, readily available, and inexpensive. The resulting cold pack makes a great endothermic chemical reaction for a science class.

The endothermic chemical reaction is:

H3C6H5O7(aq) + 3 NaHCO3(s) → 3 CO2(g) + 3 H2O(l) + Na3C6H5O7(aq)

Aqueous citric acid plus sodium bicarbonate (baking soda) reacts to form carbon dioxide gas, water, and sodium citrate. Because gas is produced, this reaction will expand a sealed plastic bag, potentially unsealing it and spilling if you fill the bag too full. Some people prefer to mix the chemicals in a cup instead.

Basically, all you do is mix together citric acid and baking soda and seal them in a bag. Then, just add water. The contents of the bag will continue to chill as the reaction proceeds, eventually returning to room temperature when the reaction is complete. It’s safe to wash the contents down the drain.

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Labbie
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Re: Citric Acid and Baking Soda Cold Pack

Post by Labbie » 06 Sep 2019, 12:52

Thats great Kimmy thank you
Regards Labbie

Lab Manager/Lab Tech, mind reading etc etc
Now retired :wub:

Smithy73
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Joined: 13 Aug 2015, 14:59
State/Location: NSW

Re: Citric Acid and Baking Soda Cold Pack

Post by Smithy73 » 09 Sep 2019, 10:47

Morning,

We do one for an exothermic reaction with iron filings, calcium chloride and water saving crystals in a zip lock bag and it heats up.

I will have to try your endothermic prac.

Thanks for sharing.

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