Honors Chemistry - Period 1
Front Row: Nina Kurose, Hannah Krauth, Annabelle Ford, Carole Chalfin-Renard, AJ Evans-Perez
Second Row: Alison Jasinski, Chris Hibbard, Stephen Cardinal, Rachel Osofsky, Nora Brown, Maria Yeskie
Third Row: Emma Cutler, Bill Frothingham, Kudrat Patel, Chelsea Langelier, Eli Parker-Martell, Becky Ross
Back Row: Harry Warner, Dan Strom, Ari Benjamin, Declan Wolfe, Alanah Driscoll-Sbar, Jesse Ross-Silverman
AP Chem - Dry Ice Bonus LAD
Just how cold is dry ice?
Very cold. -109'F = -78'CA special thanks to Scott and Christine at American Carbonation in Palmer who so generously donate the dry ice that we use.
What's so "dry" about dry ice?
Ice is really just frozen water, H2O. But dry ice is actually frozen carbon dioxide, CO2. But in particular, what makes it so "dry" is that when frozen carbon dioxide "melts" it doesn't actually melt into a liquid, it converts directly to a gas. This phase change process is called sublimation.
Why do the bubbles seem to hover in the fish tank?
Carbon dioxide is more dense than air and colorless, so after it sublimes it sits in the bottom of the fish tank even though you can't see it there. Since it sinks to the bottom, it pushes the less dense oxygen and nitrogen up out of the way. When the bubbles are blown into the tank they are sink through the air, but are less dense than the layer of carbon dioxide gas in the bottom, so the bubbles appear to be hovering in the middle, but they are actually floating on the layer of carbon dioxide.
What am I seeing when I see those cool clouds of "smoke?"
When the dry ice sublimes and turns into carbon dioxide it is a completely colorless gas that you cannot see. Water vapor, in the air all around you, is also colorless. The smoke you see is actually condensed (turned into liquid) water. As mentioned, this water vapor is already in the air as humidity. It is the same "smoke" that comes out of your mouth in the wintertime. The water that is condensing is in the air already, but since the air near the dry ice gets so cold, it is causing the water to condense, just like the cold air in wintertime causing your breath to condense.
Why does the dry ice "sing" when on the spoon? Why does it hover on the desk?
The solid piece of dry ice is constantly expelling gas on all sides of the piece of solid. The gas comes off the bottom of the piece as well. As it comes off, it causes the solid lump to raise up, but then gravity takes over and causes it to drop back down down. This occurs very quickly over and over, causing the vibrating "singing" noise. The same blanket of gas underneath the lump of dry ice causes it to seem to hover and slide so nicely like the hovering puck in an air hockey game when the puck slides on the blanket of air coming out of the tiny holes in the rink
Why does the candle go out?
You may remember that oxygen is necessary for burning. The carbon dioxide gas sits in the bottom of the beaker and pushes the air with its oxygen up and out of the way. The lack of oxygen available to the candle causes the flame to go out.
What are those bubbles under water? Is the water boiling?
No, the water is NOT boiling. The dry ice is subliming and turning into a gas under the water. The bubbles are carbon dioxide gas, which of course are less dense than water, and float to the top of the water. This is similar to bubbles that you blow out of the end of a straw.
Why is there extra smoke when we drop the dry ice in water, especially warm water?
A beaker of water naturally evaporates, especially warm water. The fact that there is extra water vapor in the air over a beaker of water makes for more "smoke" when the presence of very cold carbon dioxide gas causes the water vapor to condense. It is the condensed water vapor that we can see. The warmer the water, the more "smoke" you will observe since warmer water will have more water vapor above it.
Why does the smoke seem to sink?
The water condenses and creates the "smoke" wherever the air is cooled by the cold carbon dioxide gas. This makes the smoke follow the cold carbon dioxide gas which is more dense than air and so it sinks.
Why does the bag and balloon expand?
Remember from our previous lessons on states of matter that gases take up much more space than either solids or liquids. The requirement of more space causes the balloon and bag to expand.What is the taste of carbon dioxide?
When you stick your tongue over the "smoke" you are causing carbon dioxide to land on your tongue. This carbon dioxide dissolves in your saliva and makes carbonated water out of your saliva. Thus you should get a seltzer water sensation, since the fizz in seltzer is carbon dioxide.
AP Chemistry - Period 4
Seated in Front: Clare Rayton, Aaron Sarvet, Crystal Yu, Taylor Adams
Second Row: Mariam Paracha, Lauren Cahillane, Lauren Waslick, Julie Bartolomeo, Dana Egan-Sherry, Nora Kotruba
Third Row: Angela Ruggerio-Corliss, Bobby Eastman, Aaron Berkenwald, Matt O'Brien, Lucy Spalding
Back Row: Debby Reyes, Jon Rockett, Chris Umbach, Sigrid von Wendell, Nich Kellogg