Methods
The plastic mesh fabric was placed over the mouth of the Mason jar, and the metal screw band of the latter was fastened firmly over the plastic mesh sheet. Scissors were used to cut the edges of the plastic mesh to make it perfectly match the mouth of the Mason jar. The cut screen was placed over the mouth of the Mason jar and twisted. Using the glass pipette, the experimenter put a few drops of green food coloring into 16 oz of water. The food coloring was used to assist the observer in distinguishing the water in the Mason jar. After these preparations, water was simply poured into the Mason jar.
The index card was placed directly over the mouth of the Mason jar, then it was covered by one hand and held down securely. The water molecules began to adhere to the index card, thus causing it to stick to the surface of the plastic mesh. With one hand placed firmly over the index card on top of the mouth of the Mason jar, the experimenter used the free hand to hold and quickly invert the Mason jar by 180 degrees. A small pocket of air was now at the top (formerly, the bottom) of the Mason jar, which helped to prevent the weight of the water from pushing down the index card.
Keeping the Mason jar horizontal, the index card was steadily removed from the bottom of the jar’s mouth. Even though some water might leak out of the Mason jar, the majority of the water should stay inside. Subsequently, the Mason jar was tipped a few degrees carefully to allow air to enter it, allowing for the observation of water immediately spilling under the impact of surface tension discrepancy. As an optional procedure, a toothpick was inserted through the holes in the mesh sheet while the water remained undisturbed and still suspended in the Mason jar. Ultimately, the jar was turned over, and the water was poured out.
Results
When the Mason jar was turned over with the index card held at the bottom, one observed that it did not fall. Furthermore, when the index card was slightly removed with the Mason jar kept static, only a few drops of water fell, while the majority of the water remained in the jar. When the experimenter carefully inserted a toothpick into the jar, water also stayed in the Mason jar. Due to the fact that food coloring was used to make the water observable, the experiment was clear and accurate. As soon as the Mason jar was turned over, all the water poured out. The phenomena of atmospheric pressure and cohesion may explain these results.
Between the bottom of the jar (which became the top after the Mason jar with the index card was turned over) and the surface of the water, space formed that was filled with air and water vapor. Water tends to fall under the influence of gravity, thus increasing the volume of this space. At a constant temperature, the pressure in the Mason jar decreases in relation to atmospheric pressure. The lower this pressure, the larger the amount of fluid it can hold.
The sum of the pressure of air and water on the index card from the inside was a bit less than the atmospheric pressure from the outside. Water did not pour out of the Mason jar due to the force that arose from the difference in atmospheric pressure outside the vessel and the pressure that was formed in the bottom of the jar and the surface of the water. In other words, while the water tended to descend, a medium with reduced pressure occurred in the Mason jar, which held the liquid.
In regard to the details that require precise attention from the experimenter and viewers, it is essential to note that even a small turning of the Mason jar may lead to the water pouring completely out. If one lets any air inside the jar, then the pressure of the air inside and outside would be equalized. The air would press above and below in the same way, and the pressure difference would no longer hold the water, which would fall. This seems to be the reason for using the Mason jar and the plastic screen that tightly fits the mouth of the jar and does not allow air to get inside.
Cohesion is another physical phenomenon that is associated with this experiment with air pressure. It was observed that when the Mason jar was tilted, the water poured out due to the imbalance of air pressure. However, as soon as it was turned back to the vertical position, the liquid stopped running out. This phenomenon is based on surface tension when water molecules form hydrogen bonds and spherical droplets, which makes possible the holding of small objects such as the index card used in this experiment. Even though the attraction of water molecules could not be directly observed during this testing due to their size, it is still evident that cohesion forces affected the results.