Make a pencil mark on the card to indicate the current air pressure reading. Observe what happens as the atmospheric pressure changes over a period of time. Footnote As atmospheric pressure increases, more force is placed upon the balloon, causing it to contract into the can and the skewer indicator to rise. As atmospheric pressure decreases, the balloon will expand out of the can and the skewer will fall. The air pressure in the sealed can represents the air pressure at the time the can was sealed with the balloon.
Students can graph their results and compare graphs to other students.
Students should consult their local newspapers to obtain weather forecasts to compare with their own readings. Have the students maintain journals.