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Hot Ice or Sodium Acetate

Make Hot Ice or Sodium Acetate from Vinegar and

Baking Soda

You can supercool hot ice or sodium acetate so that it will remain a liquid below its

melting point. You can trigger crystallization on command, forming sculptures as the

liquid solidifies. The reaction is exothermic so heat is generated by the hot ice.

Sodium acetateor hot ice is an amazing chemical you can prepare yourself from baking

soda and vinegar. You can cool a solution of sodium acetate below its melting point andthen cause the liquid to crystallize. The crystallization is an exothermic process, so the

resulting ice is hot. Solidification occurs so quickly you can form sculptures as you pour

the hot ice.

Sodium Acetate or Hot Ice Materials

1 liter clear vinegar (weakacetic acid) 4 tablespoons baking soda (sodium bicarbonate)

Prepare the Sodium Acetate or Hot Ice

1. In a saucepan or large beaker, add baking soda to the vinegar, a little at a time andstirring between additions. The baking soda and vinegar react to form sodiumacetate and carbon dioxide gas. If you don't add the baking soda slowly, you'll

essentially get abaking soda and vinegar volcano, which would overflow your

container. You've made the sodium acetate, but it is too dilute to be very useful,

so you need to remove most of the water.

Here is the reaction between the baking soda and vinegar to produce the sodium

acetate:

Na+[HCO3]

+ CH3COOH CH3COO

Na

++ H2O + CO2

2. Boil the solution to concentrate the sodium acetate. You could just remove thesolution from heat once you have 100-150 ml of solution remaining, but theeasiest way to get good results is to simply boil the solution until a crystal skin or

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film starts to form on the surface. This took me about an hour on the stove over

medium heat. If you use lower heat you are less likely to get yellow or brownliquid, but it will take longer. If discoloration occurs, it's okay.

3. Once you remove the sodium acetate solution from heat, immediately cover it toprevent any further evaporation. I poured my solution into a separate container

and covered it with plastic wrap. You should not have any crystals in yoursolution. If you do have crystals, stir a very small amount of water or vinegar into

the solution, just sufficient to dissolve the crystals.

4. Place the covered container of sodium acetate solution in the refrigerator to chill.Activities Involving Hot Ice

The sodium acetate in the solution in the refrigerator is an example of a supercooled

liquid. That is, the sodium acetate exists in liquid form below its usual melting point. You

can initiate crystallization by adding a small crystal of sodium acetate or possibly even by

touching the surface of the sodium acetate solution with a spoon or finger. The

crystallization is an example of an exothermic process. Heat is released as the 'ice' forms.To demonstrate supercooling, crystallization, and heat release you could:

Drop a crystal into the container of cooled sodium acetate solution. The sodiumacetate will crystallize within seconds, working outward from where you added

the crystal. The crystal acts as a nucleation site or seed for rapid crystal growth.Although the solution just came out of the refrigerator, if you touch the container

you will find it is now warm or hot.

Pour the solution onto a shallow dish. If the hot ice does not spontaneously begincrystallization, you can touch it with a crystal of sodium acetate (you can usuallyscrape a small amount of sodium acetate from the side of the container you used

earlier). The crystallization will progress from the dish up toward where you arepouring the liquid. You can construct towers of hot ice. The towers will be warmto the touch.

You can re-melt sodium acetate and re-use it for demonstrations.Hot Ice Safety

As you would expect, sodium acetate is a safe chemical for use in demonstrations. It isused as a food additive to enhance flavor and is the active chemical in many hot packs.

The heat generated by the crystallization of a refrigerated sodium acetate solution should

not present a burn hazard.

Hot Ice Help

Answers tocommon questions about hot iceare available that should help solve any

problems you may encounter with this project. There is also avideo tutorialshowing howto make hot ice.

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Sulfuric Acid and Sugar Demonstration

Easy & Spectacular Chemistry Demonstration

One of the most spectacular chemistry demonstrations is also one of the simplest. It's thedehydration ofsugar(sucrose) withsulfuric acid. Basically, all you do to perform this

demonstration is put ordinary table sugar in a glass beaker and stir in some concentratedsulfuric acid (you can dampen the sugar with a small volume ofwaterbefore adding the

sulfuric acid). The sulfuric acid removes water from the sugar in a highly exothermic

reaction, releasing heat, steam, and sulfur oxide fumes. Aside from the sulfurous odor,

the reaction smells a lot like caramel. The white sugar turns into a black carbonized tubethat pushes itself out of the beaker. Here's a niceyoutube videofor you, if you'd like to

see what to expect.

What Happens

Sugar is a carbohydrate, so when you remove the water from the molecule, you'rebasically left with elemental carbon. The dehydration reaction is a type of elimination

reaction.

C12H22O11 (sugar) + H2SO4(sulfuric acid) 12 C (carbon) + 11 H2O (water) + mixturewater and acid

Although the sugar is dehydrated, the water isn't 'lost' in the reaction. Some of it remainsas a liquid in the acid. Since the reaction is exothermic, much of the water is boiled off as

steam.

Safety PrecautionsIf you do this demonstration, use proper safety precautions. Whenever you deal with

concentrated sulfuric acid, you should wear gloves, eye protection, and a lab coat.Consider the beaker a loss, since scraping burnt sugar and carbon off of it isn't an easy

task. It's preferable to perform the demonstration inside of a fume hood.

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