How to Get Dry Ice to Change Color?

To get dry ice to appear to change color, you need to use a pH indicator solution. Dry ice, which is solid carbon dioxide (CO2), sublimates into gaseous CO2. When this CO2 dissolves in water, it forms a slightly acidic solution of carbonic acid. A pH indicator is a substance that changes color depending on the acidity or alkalinity (pH) of the solution it's in.

Understanding the Process

Here's a breakdown of how it works:

• Dry Ice Sublimation: Dry ice doesn't melt; it goes directly from a solid to a gas (sublimation).
• CO2 Dissolving in Water: When CO2 gas dissolves in water (H2O), it reacts to form carbonic acid (H2CO3).
• Acidic Solution: Carbonic acid makes the water slightly acidic.
• pH Indicators: These substances change color based on the pH of the solution.

Methods to Change the Color

Here are a couple of ways you can demonstrate a color change with dry ice:

1. Using Universal Indicator

Universal indicator is a mixture of several pH indicators that exhibit a range of colors depending on the pH level.

• Materials:

  • Dry ice
  • Water
  • Universal indicator solution
  • A clear container

• Procedure:

  1. Add water to the container.
  2. Add a few drops of universal indicator to the water. The water will likely turn green (neutral pH).
  3. Carefully add a small piece of dry ice to the water.
  4. Observe the color change. As the CO2 dissolves and forms carbonic acid, the solution will become more acidic and the universal indicator will change color. You should see the solution turning yellow, then possibly orange, and even red as the acidity increases.

2. Using Red Cabbage Juice

Red cabbage juice is a natural pH indicator.

• Materials:

  • Dry ice
  • Water
  • Red cabbage
  • A clear container

• Procedure:

  1. Make the Red Cabbage Indicator: Chop a red cabbage and boil it in water until the water turns a deep purple/red color. Strain the liquid and let it cool. This is your red cabbage indicator.
  2. Add the red cabbage indicator to the container.
  3. Carefully add a small piece of dry ice to the water.
  4. Observe the color change. As the CO2 dissolves, the solution will become more acidic, and the red cabbage indicator will change color from purple/red to pink.

Safety Precautions

• Handle dry ice with care: It is extremely cold and can cause frostbite. Use gloves or tongs when handling it.
• Do not ingest dry ice: It can cause serious internal damage.
• Perform experiments in a well-ventilated area: As dry ice sublimates, it releases carbon dioxide gas, which can displace oxygen.

By using pH indicators, you can visually demonstrate the change in acidity caused by dry ice dissolving in water, resulting in a color change.