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Wonderful Weather - Experiment 5

1. Cloud in a bottle | 2. Tornado in a Bottle | 3 Air Pressure in a Jar | 4. Air Pressure on a glass | 5. Make a barometer  | 6. Make a Thermometer

Experiment: To make a barometer

Materials:

You will need:

1 empty jar
1 large balloon
1 straw
1 cocktail stick
Glue (Pritt)
String
Pencil
Ruler
Piece of card
Scissors

 

Method:

What you have to do: 

1) With your scissors, cut the bottom bit off your balloon - the bit you blow through.
Stretch the balloon tightly on top of the jar.

2) To make sure that the balloon is on firmly, tie your string around the top of the jar. It is really important that the balloon is stretched tightly.

3) Cut off a small section of straw (just enough to reach from the middle of the jar <balloon>) to the edge.

4) Glue the straw in place.

5) Glue your cocktail stick into the straw so that half of it sticks out. This will be your pointer.

6) Fold your piece of A4 card in two and place it beside the jar. Where the cocktail stick touches the card, mark a line. Above the line, write 'High Pressure' and below the line write 'Low Pressure'.

Result: If there is High Pressure over the country, the cocktail stick will point up (above the line) because the pressure on the balloon is pushing down. If there is Low Pressure over the country, the cocktail stick will point down.

Conclusion: If the pressure outside the jar is greater that the pressure inside the jar, it will press against the balloon and that will force the cocktail stick to point up. If the pressure inside the jar is greater than the pressure outside the jar, it will push against the balloon from inside the jar and the cocktail stick will be forced down.