Dry Ice Experience: Beauty and Cold
The focus of dry ice is that from a solid state it immediately passes into a gaseous state without an intermediate liquid phase (this process is called sublimation). The sublimation temperature of carbon dioxide is -78.5 ° C. Dry ice is freely sold in two forms - briquettes and granules. For experiments, it is more convenient to use granules, since they are small in size, they are easier to dose. On the other hand, dry ice is a consumable: up to 15% of its mass evaporates in a foam container per day.
Principle of experience
Most of the experiments with dry ice are based on the same principle. The fact is that upon contact with water, dry ice begins to rapidly transform from a solid to a gaseous state, and it looks like boiling, only with much brighter and more characteristic vaporization. Moreover, the evaporating carbon dioxide is heavier than air (density 1.9768 kg / m3 versus 1.225 kg / m3), and therefore the "smoke" spreads over the surface surrounding the container with water, and does not rise up.
The experimenter pours water into the container and then throws ice there. The warmer the water, the faster the ice will evaporate, the shorter and visually spectacular the reaction. This is where the division into experimental areas arises. The first option is to allow the ice pair to calmly go outside and watch its spread.
The second option is to limit the distribution area of steam, that is, in other words, to evaporate ice in a confined space. If you do this, for example, in a closed plastic bottle, a cork will be knocked out of it (or it will break at all - never repeat this!), Since in the gaseous state CO2 takes up much more space (gas density, recall, 1.9768 kg / m3, and solid phase - 1560 kg / m3). But to do this with bottles is quite dangerous, much more interesting and easier to inflate a carbon dioxide soap bubble.
With proper use, dry ice is completely safe, like regular water ice. But you must follow certain precautions:
1) Be sure to use gloves and never allow prolonged contact of dry ice with skin. Its temperature is -78.5 C below zero, and you can get a cold burn. Simple cloth gloves are enough.
2) When transporting and storing ice, be sure to leave two or three small holes with a diameter of a couple of millimeters in the container. This will prevent the container from bursting. Never put ice in an airtight container.
3) Try to breathe in a minimum of CO2 vapor - this can cause a headache.The article “Catching Ice Smoke” was published in the magazine Popular Mechanics (No. 3, March 2014).