First, cut a large piece of the balloon.

Then, tight the balloon onto the opening of jar.

Secure the opening of jar with a rubber band.

Tape the jar with sellotape to make sure no air can enter again.

Then, tape the straw on the balloon with sellotape.

Fold the card into prism with triangle cross section.

Paste a sun picture above the normal line and a cloud

picture under the normal line.

Lastly, place the barometer model at a place with constant

temperature and without direct sunlight.

On the sunny day, the temperature outside of the jar is higher and the

atmospheric pressure is also higher. Thus, it pushes the balloon on the jar

inwards. This is why the straw will moves up when sunny day.

On the raining day, the temperature outside of the jar is lower and the

atmospheric pressure is also low. Thus, the higher pressure in the jar pushes the

balloon upward. This is why the straw moves downward when raining day.

The making of barometer is based on the principle of

air pressure.

Websites:1.http://www.ehow.com/video_4419382_supplies-

making-barometer.html2.http://www.youtube.com/watch?v=e0j7IfDtv7o3.http://www.ehow.com/video_4419389_mark-

barometer-gauge.html4.http://www.ehow.com/video_4419385_make-

barometer-jar-balloons.html5.http://www.youtube.com/watch?v=CbjqeiL5eKc&featur

e=relmfu

6. http://spoonful.com/crafts/balloon-barometer