Dry ice experiments!

Session focus: Acidic properties of non-metal oxides, sublimation and pressure

In this first experiment, we decided to do a twist on the classic dry ice experiemnt by adding Sodium Hydroxide and Universal indicator to water, to first form an alkaine solution. Then, we let the students add dry ice into the solution, resulting in a gradual colour change from purple to yellow as the pH was reduced. The science behind this, we explained, was that the dry ice (solid carbon dioxide ), as a non-metal oxide, reacted with water to produce an acid, which leads to the solution becoming more acidic.

In this experiment, a soap bubble is filled with carbon dioxide gas released from the sublimation of dry ice. As increasing amounts of carbon dioxide gas molecules fill the bubble, a pressure gradient between the inside and the outside of the bubble is formed. The higher pressure inside the bubble pushes against the lower pressure outside. Eventually, the pressure generated within the bubble causes it burst!

Materials needed

• Dry ice
• Water
• Measuring cylinders
• Universal indicator (or other pH indicators)
• Gloves
• Beaker

How to make the dry ice bubbles

Equipment:
• Large water bottle
• Plastic tube
• Dish Soap
• Cutter

Instructions:
• Use a cutter to create a hole in the lid of the bottle
• Insert the tube into the bottle
• Fill the bottle a quarter of the way with water
• Pour a small volume of dish soap into a beaker
• Add dry ice into the water inside of the bottle
• Slightly unscrew the lid and dip the end of the tube into the dish soap enough to coat it
• Screw the lid shut and let the carbon dioxide gas flow into the bubble!