Observations & Explanations for the Teacher
1. For this situation, the dry ice will float across the table like an air-hockey puck. This is because the "warm" table is causing the dry ice to sublime and produce a "cushion" of carbon dioxide gas for the dry ice to float on.
2. The density of the dry ice vapor is higher than the density of regular air, so the bubbles will float on top of the vapor. Since the vapor is invisible, it will appear that the bubbles are floating in the middle of the beaker, unsupported.
3. Placing a coin on edge in the dry ice causes the dry ice to sublime where the "hot" coin touches the ice, causes a burst of vapors to push the coin away. This happens on both sides of the coin in rapid succession, making the coin vibrate.
4. Sublimation inside a closed container builds up gas pressure, which eventually pops the top off of the film canister.
5. Universal indicator will be a violet color in a basic solution of NaOH. As the carbon dioxide interacts with the water, it forms carbonic acid, thus acidifying the solution and causing the indicated color to shift to green and finally to pink.