You will need:
One jam jar
One clear plastic straw
Some modelling clay or blue-tack
A few drops of food colouring
Permanent marker - A water proof pen which can write on the clear plastic straw
Using the ruler and the pen mark off measurements on the straw showing centimetres and half centimetres. The more accurately you can do this the more accurate your barometer will be.
- Half fill the jam jar with cold water and add a few drops of food colouring.
- Dip the straw into the water until the water is up to the 0cm mark and stuff the end of the straw with modelling clay or blue-tack so that the water hangs at the 0cm mark. You may need to practice this a little to get it right.
- Then pull the straw up and out of the water vertically by about 5cm. The water should stay in the straw at the 0cm mark. Then stick the straw to the inside of the jar upright using the sticky tape.
- Place your barometer inside your house somewhere where it will not get knocked over, is out of direct sunlight and away from radiators.
Your barometer is finished! Over the next few days take a look at the water level in the straw. The water in the straw will rise and drop depending on the air pressure. When the air pressure is lower than it was on the day you began, the water in the straw will drop giving you a negative reading. When the air pressure is higher than it was on the day you began, the water level in the straw will go up giving you a positive reading. The more the water moves in the straw the greater the difference in air pressure.
Low air pressure usually means rain in the UK. High air pressure usually means fine clear weather. High pressure in the winter can often mean very cold days and nights; high pressure in the summer often means very warm weather!
Do you want to know more about weather systems and pressure? Take a look at the web links section for more information.