Drinking bird – heat energy STEM activity

The drinking bird is a happy little party toy that has been around since the 1920s. The cute bird has a glass body, a felt head, and a top hat. The mysterious ability to drink water from a cup over and over again has an explanation using chemistry and physics!

Safety note: Be sure to explain safety precautions to children. This experiment uses a thin glass container containing a substance similar to paint stripper. Eye and skin protection should be used if broken. Disclaimer: All information provided on this site is for entertainment and education purposes only. Using any information from thecasabouquet.com is at your own risk.

Instructions for drinking bird

• Carefully insert the metal “arms” of the drinking bird into the slots on the plastic legs. Make sure it can swing freely.

  

  

  
  
• Try different cups with the bird. When the bird is horizontal, its beak should just touch the water in the cup. If your cup is too small, you may have to put something under it to lift it up. Or you may lift the drinking bird to make it work with a larger cup.

  

  

  
  
• Gently hold the bottom bulb of the bird in the palm of your hand. Observe what happens to the liquid in the tube. Is the bulb heating or cooling from your hand?
• Put cold water in the cup. Wet the bird’s head entirely. Keep dipping its beak until the water moves throughout the felt.
• Measure the temperature of the water and the temperature of the room.
• Place the cup in front of the bird. Observe what happens to the liquid in the body. Where is the liquid when the bird dips? Where is it when the bird stands up? How long does a whole cycle take?

What questions can you answer with an experiment like this? Do the temperature of the water and the room make a difference? How can you make water evaporate from the head more quickly? How can you warm or cool the tail and what happens? Does the drinking cup have to be clear?

Supplies

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• Drinking bird
• Small cup, 3 inches high
• Washers or coins
• thermometer or temperature probe
• paper or notebook for recording results, pen

Tips for teachers: 1) Put some washers or coins on the bird’s base to keep it from tipping over. 2) Children should not handle the bird, the glass is delicate and the liquid inside is caustic. 3) The metal collar around the tube can be moved up down, carefully! If the liquid in the tube moves but the bird doesn’t dip, you may need to move the collar down. 4) The bird needs a small glass but should not dip lower than horizontal. You may need a box or book to raise the cup or raise the bird.

What is the science?

Content: thermodynamics, ideal gas law, pressure, temperature, evaporation, condensation

The drinking bird is an example of a heat engine. The system is two glass bulbs (head and tail) with a tube between. Inside is the liquid and vapor (gas) evaporated from that liquid. The liquid is dichloromethane, CH₂Cl₂. Water evaporates from the felt on the head causing the temperature of the head to decrease. Gas vapor in the head condenses and the pressure inside the head drops. The liquid in the bottom can then start moving up and tips the bird over.

The boiling point of dichloromethane is 103 degrees Fahrenheit, helping the bird work at room temperature. The ideal gas law PV=nRT can be used to describe the changes in pressure and temperature in the bird.

Resource links

• https://www.khanacademy.org/science/chemistry/gases-and-kinetic-molecular-theory/ideal-gas-laws/v/ideal-gas-equation-pv-nrt
• Ideal gas law video from Khan Academy

I’ll be looking for comments below, or contact me at lisa [at] casabouquet[dot]com.

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