IN THIS EXPERIMENT YOU FILL A PREFROM WITH WATER AND PUT A DRINKING STRAW INTO THE PREFROM AND USE CLAY TO SEAL THE OPENING.
It is important to recall that when you first tried it, you were unable to drink, but a small amount of water entered the straw. When the water goes into the straw, what happens to the volume of water in the sealed bottle? How is this related to the properties (P,V) of the gas above the water?
I've not done this experiment but I assume if water enters the straw that the water level in the bottle will decrease, the volume of air above the water must increase, and the pressure must decrease.
When water enters the straw, the volume of water in the sealed bottle decreases. This is because when you insert the straw into the bottle and seal it with clay, the air trapped inside the bottle creates a closed system. As you try to drink through the straw, you create a partial vacuum within the straw, causing the air pressure inside the bottle to decrease.
According to Boyle's Law, which describes the relationship between the pressure and volume of a gas at constant temperature, when the pressure of a gas decreases, its volume increases. In this case, as the air pressure inside the bottle decreases due to the suction created by attempting to drink from the straw, the volume of the gas above the water increases.
The water entering the straw is a result of the increased volume of the gas inside the bottle. As the gas expands, it displaces some of the water, forcing it to move up the straw and ultimately into your mouth.
Therefore, the volume of water in the sealed bottle decreases when water enters the straw, and this is directly related to the change in volume of the gas above the water due to the decrease in pressure.