Topic: Gas Dynamics

Making a barometer



Learning how to predict the weather with a barometer.


Air pressure is influenced by temperature and density. When air is heated, the particles expand. This reduces its density relative to the cooler particles around it. As a result, the warmer air rises leaving a low pressure gap underneath it.

A barometer is a tool used to measure atmospheric pressure which can be used to help predict the weather. A barometer works by sealing a chamber of air in a flexible material that is able to expand or contract. The material caves in or bulges outward depending on whether the higher pressure is outside or inside the chamber. A needle can be attached to this flexible material – the will move up and down to reflect air pressure.


  • A jar
  • A balloon
  • Strong elastic band
  • Uncooked spaghetti noodle
  • Sheet of paper
  • Marker



Cut the stem off the balloon


Stretch the balloon over the opening of the jar


Secure the balloon to the jar with the elastic


Attach the uncooked spaghetti to the center of the stretched balloon


Stick a piece of paper on the wall and place the jar in front of it. Make a mark on the paper to represent where the spaghetti is pointing


Monitor the jar over several weeks, marking where the spaghetti is on the piece of paper. Does it change day to day? Is there any relationship to the weather?