Marvin and Milo

Explore physics the exciting way, by trying out a simple and fun experiment. This month, Microwave marathon Don't forget to check back next month for the next edition...

‹Prev Sound of gasNext›

print this page button Print this page


What you need


A small glass bottle


An effervescent indigestion tablet



  1. Pour about 2cm of water into the bottle. Blow across the top of the bottle and listen carefully to the sound it makes.
  2. Break the tablet in two, and put both halves into the bottle.  Wash your hands while you wait for it to stop fizzing.
  3. Blow across the top of the bottle again and listen to the sound it makes now.



Results & explanation

Sound travels more slowly through carbon dioxide (the gas given off by the fizzing tablet) than through air, so when you blow across the bottle you hear a lower pitched note.

Find our favourite websites on  the speed of sound with


Buy our book



Marvin & Milo on facebook


The folowing links are external