How to Construct a Barometer
- 1). Blow up the balloon and let out the air to stretch the rubber. Then cut off and discard the neck of the balloon.
- 2). Cover the mouth of the jar with the balloon. Make sure the balloon is stretched tightly.
- 3). Wrap the rubber band around the mouth of the jar to fasten the balloon. This creates a seal that makes the jar airtight.
- 4). Flatten the last inch of one of the ends of the straw, then make a diagonal cut to form a pointed tip. Carefully cement the uncut end of the straw to the center of the balloon so that the straw extends about 6 inches beyond the edge of the jar and is parallel with the ground.
- 5). Fold the sheet of construction paper into thirds and tape the ends together to make a triangular stand. Place the stand upright next to the jar so that the tip of the straw just touches it.
- 6). Mark the initial position of the straw on the paper stand and note the current weather conditions. If the air pressure drops, the straw will point downwards to indicate stormy weather. If the air pressure increases, the straw will point above the initial mark to indicate calmer weather.
