The expression “hot ice” itself hardly fits our minds. After all, we are used to the fact that ice, no matter, is a small cube in a glass or a huge iceberg in the ocean, ice. And here for some reason it’s hot. We will figure out what kind of substance it is, how it turns out and conduct an experiment at home. So - hot ice.
A substance with the same name
Everyone knows that ice is water, which is in a solid state of aggregation, into which it passes already at 0 ° C. But, conducting experiments on water, the English physicist Bridgman discovered that under great pressure there is a restructuring of the crystal lattice, it becomes more dense.
Under a pressure of slightly less than 21 thousand atmospheres, water becomes ice already at a temperature of +76 ° C. And at 30 thousand atmospheres - at 180 ° C! This is really hot ice. You can get burned a lot. But it is impossible to touch it, because such pressure to withstand a person is unrealistic. Physicists study the properties of such ice only indirectly.
Thanks to the experiments, the Englishman determined that there are several types of ice, where under grade I there is everyone’s familiar ice formed at zero, and then, with increasing pressure, passes from one variety to another. At 30 thousand atmospheres, it becomes grade VII. Since the crystal lattice changes, the properties of hot ice are different. It is heavier than water and its density is 1.05 g / cm 3 .
Another substance with the same name
Conducting a Hot Ice experiment at home to test Bridgman’s theory will naturally fail. But chemistry as a science offers you a different experience, no less spectacular.
It’s called “Hot Ice”. Sodium acetate is a substance that you will need to carry it out. Did not hear? And in the kitchen, we often get it in the preparation of various pastries, mixing soda and vinegar. It remains only to figure out how to make hot ice from this foam. Let's get it right.
Formula and reaction equation
Sodium acetate (also called sodium salt of acetic acid) is a white crystals with a slightly salty taste and smell that resembles acetic acid. Its formula is CH 3 COONa. In the laboratory, the salt is obtained from acetic acid and carbonates, sodium hydroxide or sodium bicarbonate.
Who cares, the reaction equation is as follows:
CH 3 COOH + NaHCO 3 → CH 3 -COON a + H 2 O + CO 2
Mistresses know that the percentage of acetic acid can be different. But there is no difference what you will find in a cabinet in the kitchen, you just need a different amount of soda. The proportions are as follows:
- 750 g of vinegar 8% and 84 grams of soda;
- 86 g of essence 70% and 84 grams of soda;
- 200 g of vinegar 30% and 87.4 g of soda.
As a result of the reaction, we get a solution, but by evaporating water we will get 82 g of sodium acetate in the form of crystals.
Chemistry is a science that does not tolerate the option of "pour on the eye." If you want the Hot Ice chemical experiment to succeed, make a proportion of the substances using a scale. More accurate are electronic.
Experience at home
Since acid is used in the experiment, and the Hot Ice experiment also requires heating to high temperatures, the presence of adults is mandatory. So, let's start witchcraft.
Cooking "Hot ice" at home.
- In a small enameled saucepan, mix vinegar and soda in the above proportions, depending on the percentage of vinegar found in the kitchen. Put it on the stove, on a small fire and slightly heat the resulting witch's brew. Get ready, there will be a lot of foam, but as soon as the reaction passes and water and sodium acetate remain in the pan, the solution will become completely transparent.
- Be sure to check if your solution is ready by dropping a drop of vinegar. Has foam appeared? So, initially the wrong weight of soda was taken, we continue to add a little vinegar, until the foam stops appearing. Well, if the smell of vinegar is very strong in the nose, it means that a lot of acetic acid was taken initially. Add a little soda to the solution until the foam ceases to form in the saucepan, otherwise the smell of vinegar from the apartment will have to weather out for a long time.
- Only when the foam has stopped rising, can the pan with the brew be set on fire to remove excess water from it. Do not forget to follow what is happening. As soon as a crust similar to ice begins to form on the surface, immediately remove the container from the heat and leave it alone for 5 minutes.
- While the witching drink cools, we put water in a kettle to boil. Then slowly, literally drop by drop, we begin to pour boiling water into the already cooled mixture, alternating the addition with stirring. We do the procedure until the crust and all visible pieces are completely dissolved. The solution should be completely transparent, but at the same time slightly viscous.
- We take an absolutely clean container and pour a small amount of substance from the saucepan into it. If the jar or mug turns out to be dirty - the solution will begin to crystallize not when you want, but for now it will cool. We put in the refrigerator and cool to room temperature. You need to understand that we have obtained a supersaturated solution, so that now the temperature of the crystallization process is lower than usual.
- Chilled? Here it is, the moment of truth. It's time to embark on the mystery of the formation of hot ice!
Touch a chilled brew with a toothpick dipped in sharp salt. If everything is done correctly, the solution will begin to harden, forming a pattern of crystals similar to ice, each time a new and unique one. This releases a large amount of energy, which you will feel like a wave of heat.
After the formation of hot ice, it can be used to repeat the experiment. Just place the container in a water bath and start stirring with a spoon. Did you see that a crust of crystals formed? Repeat steps 4-6 and enjoy the result again and again.
Why didn’t the experiment turn out? Error handling
There are not so many options why the experiment did not turn out, but we will consider them all:
- In the reaction of soda with vinegar, some reagent was in excess and influenced the further preparation of the supersaturated solution. Next time, carefully monitor the amount of substances during cooking or just buy the sodium salt of acetic acid in a ready-made form.
- The container in which the prepared solution was cooled turned out to be contaminated.
- Too late, the saucepan was removed from the fire, or the crust formed was not completely dissolved.
Where is this reaction used?
The Hot Ice experience itself has practical applications as well, it is precisely a supersaturated solution that is used in chemical heating pads and heaters, which even at room temperature, as you yourself saw, does not go into the solid phase.
Only in heaters do you act on the solution not with a toothpick, but with a special disk (most often a metal one). During the transition of the supersaturated solution to the solid phase, from 264 to 289 kJ / kg are released. So you have formed a "hot" ice, and the heating pad acts on the body with the generated heat, while the burn is excluded, since the allocated temperature is not enough.
By the way, as a heat source, a supersaturated solution of sodium acetate is also used in some models of spacesuits. "Hot ice" rules.