The Science of Dry Ice and Singing Spoons

Safety Note: Dry ice is extremely cold (-78.5°C). Never touch it with bare skin—always use tongs and heavy-duty gloves. Ensure you are working in a well-ventilated area.

When you press a warm metal spoon against dry ice, it screams, squeals, or “sings.” This noisy phenomenon is caused by a combination of sublimation and rapid vibration.

Why does it scream?

Dry ice is solid carbon dioxide (CO₂). Unlike water ice, it doesn’t melt into a liquid; it sublimates, turning directly into a gas.

• Thermal Energy Transfer: The spoon is much warmer than the dry ice. When they touch, heat flows rapidly from the metal into the ice, causing it to sublimate at an incredible rate.
• Gas Pressure: A tiny layer of CO₂ gas forms instantly between the spoon and the ice. This gas pushes the spoon away.
• High-Frequency Vibration: As the spoon is pushed away, the pressure drops, and the spoon falls back onto the ice. This happens thousands of times per second. These rapid collisions create sound waves that we hear as a high-pitched squeal.

Variables to test

Find out more on variables here.

• Thermal Conductivity
  Try plastic vs. metal spoons. Metal is a great conductor of heat, while plastic is an insulator. Does the plastic spoon stay silent because it can’t transfer heat fast enough to cause rapid sublimation?
• Surface Area and Mass
  Try small vs. large pieces of dry ice. Does the mass of the ice or the size of the contact point change the pitch or volume of the sound?
• Applied Pressure
  What happens if you press the spoon down harder? Does increasing the force change the frequency of the vibrations and result in a higher or lower pitch?
• Initial Temperature
  Try dipping the spoon in hot water before touching the ice. Does the increase in thermal energy make the reaction more violent or the sound louder?

To ensure a fair test, try to use the same type of spoon when testing different pieces of ice, so you know the change in sound is only due to the ice itself!