"Dry ice" experiment
How dry ice reacts with water and indicators
The very name DRY ICE sounds a little strange, doesn’t it? We’re used to ice melting rapidly and turning into ordinary water… But here it’s all a lot more complicated. Yes, dry ice is actually gas! So this ice doesn’t melt, but sublimes – it moves right from a solid state to a gaseous state! In this experiment, we examine different physical and chemical properties of dry ice.
Reagents and equipment:
- dry ice;
- distilled water;
- liquid soap;
- glass bowl;
- 3 beakers.
Take a piece of dry ice and place it on a metal spoon. After a few seconds, it will start to jump and shake. Then put the dry ice in the glass bowl with water and observe the violent release of gas bubbles and white smoke. If you add a few drops of dish-washing liquid to the water, then a thick foam of soap bubbles full of white smoke appears. Then take 3 beakers with indicator solutions: indigo carmine – a solution of an indigo color, phenolphthalein, which is colorless, and litmus, of a red-orange color. Then add a little sodium hydroxide, and the solutions change their color: the indigo carmine turns green, the phenolphthalein turns crimson, and the litmus turns blue. Add several pieces of dry ice to each beaker. After a while, observe the solutions change back to their original color.
Dry ice is a very simple substance, the solid phase of CO₂. It is widely available and used to transport food products or clean industrial surfaces. But in the home laboratory, dry ice becomes an invaluable source of experiments. The trick of dry ice lies in the fact that it moves immediately from a solid phase to a gas phase, without an intermediary liquid phase (this process is known as sublimation). The temperature of the sublimation of carbon dioxide is -78,5°С.
On contact with water, dry ice starts to transform violently from a solid phase to a gas phase, which looks like boiling, only with a much more pronounced formation of steam. The carbon dioxide that evaporates is heavier than air (a density of 1.9768 kg/m3 as opposed to 1.225 kg/m³), and so the “smoke” settles on the surface, surrounding the container of water, and does not rise.
When liquid soap is added, the bubbles of the released gas quickly cause it to froth, and a thick foam filled with white carbon dioxide gas forms.
If you place dry ice on a metal surface, it will jump and shake. This happens because the metal surface is warm, and the dry ice sublimes very quickly on its surface, forming sources of high pressure, which causes the piece of dry ice to jump.
In the sublimation of dry ice in water, the carbon dioxide released reacts with water, forming carbonic acid and changing the acidity. This property of dry ice can be used for impressive colorful transformations with indicator solutions. The indicator solution of indigo carmine is blue in a neutral medium, phenolphthalein is colorless, and litmus is red-orange. When sodium hydroxide is added, the medium becomes alkaline, and the solutions change their colors to green, crimson and blue respectively. When pieces of dry ice are added to the alkaline solution, carbonic acid forms, the acidity of the solutions rises, the medium becomes neutral and the solutions return to their original colors.
Use gloves and never let dry ice touch the skin for a long period of time. It has a temperature of -78,5 С, and you may receive a cold burn. Try not to breathe in CO2 gas – it may cause headaches.
Warning! Substances of this experiment are toxic and highly dangerous for your health. Do not try this at home. Only under professional supervision.