Just what can dry ice do? Let’s talk about it!
Reagents and equipment: glass container, dry ice (solid carbon dioxide), candles, bowl of hot water, balloon, aqueous alkaline solutions with indicators.
Put some dry ice in a glass container and wait one minute. “Pour” the gas on some burning candles. The candles should go out!
Place a few pieces of dry ice in a balloon. Put the balloon in some hot water. After a while, an invisible force should inflate the balloon!
Take a few glasses containing indicators dissolved in alkaline solutions: litmus, phenolphthalein, and thymol blue. Drop a piece of dry ice into each glass. After a few minutes, the solutions’ colors should change!
Dry ice is a solid state of carbon dioxide. It forms at a temperature of -78.5 °C (-109°F). At room temperature, dry ice transitions rapidly from its solid to its gaseous state. Carbon dioxide gas is heavier than air, so it settles in a glass container and can be “poured” on candles. Carbon dioxide doesn’t facilitate burning, so the candles go out.
The warmer the medium, the faster the dry ice becomes gaseous, so solid carbon dioxide easily inflates a balloon when put in hot water.
If you toss some dry ice in water, some of the carbon dioxide will dissolve and form carbonic acid:

СО2 + Н2О = Н2СО3


The latter splits into ions in water, releasing some protons:

Н2СО3 = НСО3- + Н+
НСО3- = СО32- + Н+

These protons neutralize the alkaline indicator solutions. When all of the alkali is neutralized, the environment gradually becomes acidic due to the excess of protons H+.
This makes the pH indicators change colors.
Safety precautions: Do not attempt! Perform this experiment only with professional supervision.

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