Experiment – Dry ice sublimation
Video : http://archive.teachfind.com/ttv/www.teachers.tv/videos/dry-ice-sublimation.html
We will demonstrate and explain the sublimation process and the interesting effects of this process.
In a 1000 ml flat-bottomed flask, pour 500 ml hot water. Then before introducing dry ice, add some food coloring for contrast. Carefully insert the dry ice. Analyze together with the students, the reactions and explain the process of sublimation.
Observation no. 1 – Immediately after dry ice is inserted, the first thing you notice is the creation of white clouds formed from water vapor, which will be erupting from the flask.
Explanation: These white clouds are formed due to the temperature difference between hot water (about 100 degrees Celsius) and ice (-78 degrees Celsius).
Observation no. 2 – Water vapor goes down, not up.
Explanation: due to much higher density of carbon dioxide vapors do not rise, but are dragged down. CO2 is denser than air.
Observation no. 3 – Sublimation. If you raise the glass flask and watch its bottom, you will see that pieces of ice pass directly from a solid state into a gaseous state.
Explanation: ublimation is an endothermic process, thus heat absorption occurs.
To observe the large amount of CO2 removed by sublimation, we can use a glove to cover the mouth of the container. Within seconds, the glove will swell and burst.
Safety tips for the teacher and students:
- Use gloves and protective glasses when you handle dry ice.
- The packaging of dry ice is made of bubble wrap to hold out a while longer.
- The experiment must be done outdoors. If you are not able to do it outdoors, use a chemistry laboratory with open windows, and use a much smaller amount of dry ice.