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Things to try with Dry Ice: Dry Ice is one of the most entertaining chemicals of all of chemistry-dom (in our humble opinion). We believe that you will GREATLY enjoy these experiments!! But first! Some safety precautions! Dry Ice is VERY COLD - it is MINUS 110 deg F. This is easily cold enough to give you frostbite if you touch it for a more than just a second. ALWAYS have an adult present, and handle dry ice with your heavy winter gloves to make sure you don't hurt yourself! WHERE to get Dry Ice: King Soopers or Wal Mart both sell dry ice. It sells for about $0.99/lb and is available all year round. Some simple experiments: 1. Break up a chunk of dry ice and set the flattest part face down on a smooth surface (like a countertop, or tile, or linoleum). Breathe on the dry ice - do you see the fog? 2. Wait for a few minutes, and then start pushing the dry ice around with your finger. If you wait long enough, the dry ice will start to glide across the surface like an air hockey puck. 3. Take a quarter and push it perpendicularly into the dry ice. Let go. The quarter should start to "chatter" back and forth. 4. Take a medicine dropper and drop some water onto the dry ice - what happens to the water? Why doesn't it freeze when it hits the surface? 5. Put a piece of dry ice in a zip lock baggie or a balloon. Seal and wait. 6. Take a glass of water and plop it in. (Then try with hot water and then with cold water - do you see a difference?) 7. Add some food coloring to the water - does the food coloring color the fog too? 8. Add some dishwashing detergent to the water (make sure this experiment is done in the sink, or somewhere you can make a mess!) 9. Take a CLEAN CUP and add some non carbonated liquid that is suitable for drinking (ie. water, orange juice, tea, apple juice, etc.). Add a chunk of dry ice and wait until the dry ice is completely gone. Now, taste the liquid. Does it taste different than normal? 10. If you have a large enough piece of dry ice, you can try this experiment. Put the dry ice in an empty cooler, or box, or aquarium. Allow it to sit in the box for at least 30 minutes. Now take some bubble solution and blow bubbles into the container. The bubbles will float on top of the carbon dioxide gas that has been released by the dry ice. This is because dry ice is heavier than air! 11. Try our Acid/Base Indicator reaction with Red Zinger Tea! Cool!
Some Bubbling Dry Ice/Acid-Base Indicators if you have access to a chemist: Description Pieces of dry ice are dropped into several tall cylinders containing liquids of various colors. As the dry ice bubbles through the liquids, they change colors. Explanation The solutions contain sodium hydroxide (NaOH), a base, and indicators, compounds which change color when going from a high pH to a low pH, or vice versa. The sodium hydroxide produces hydroxide ions in solution, making it alkaline, or high pH, and keeps the indicator in its anion form (In-).
When dry ice (solid carbon dioxide, CO2) is added, most of it produces carbon dioxide gas, giving the bubbles, but some of it reacts with water to form carbonic acid (H2CO3).
The carbonic acid reacts with the hydroxide ion, neutralizing it and lowering the pH.
When all the hydroxide is gone, the dry ice continues to produce carbonic acid which, being a weak acid, produces hydronium ions (H3O+) and continues to lower the pH.
As the hydronium ions increase, they force the indicator into its neutral form (HIn), which is a different color than its anion form.
The following table shows some of the indicators used. Above a certain pH they are one color in their anion form, and as the pH drops below a certain value, they change to another color in their neutral form.
still have questions? email us! explanation furnished by UCCS's Dr. David Anderson
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In- + H2O
H2CO3