PTNS-101 — Assignment: Lesson 2
Phase Transition: Sublimation
A few of my pure-blood classmates had never heard of dry ice before, so I decided to purchase some from the muggle world and show them how fascinating it is with the process of sublimation (where it transitions from a solid → to gas).
Dry ice is the solid, frozen form of carbon dioxide (CO2), which is a molecule that consists of one carbon atom and two oxygen atoms. It’s colourless, non-flammable, and has a density of between 1.4 and 1.6 g/cm3. As the surface temperature of a block of dry ice is -78.5°C, I made sure to put on my dragon-hide gloves before handling them to prevent frostbite.
As I placed the chunks of dry ice in my pewter cauldron, my pure-blood classmates gathered round in anticipation of my concoction. I then carefully poured room temperature water from a watering can into the cauldron, and almost instantaneously, it started bubbling and everyone wowed in astonishment seeing it sublime into a gaseous state!
Since carbon dioxide is heavier than air, it created a cascading effect of overflowing the cauldron and spilling onto the table and floor. We ran our hands through the gas, feeling the coolness flow between our fingers. It was much colder than water ice and it didn’t leave any residue as it changed directly to a gas.
At the end of it, they remarked that the Muggle world seemed phenomenal after all, but I assured them that the wizarding world is so much more astonishing.