Has anyone ever done an experiment called "The Cartesian Diver"? The instructions are below, just in case... 1. The medicine dropper is the "diver" which will be put into the water. 2. Fill the graduated cylinder with water to about an inch from the top. 3. Fill the medicine dropper almost the entire way with water. You may need to turn it over and fill it to get enough water into the dropper. 4. Place the diver into the graduated cylinder. It should just float on top of the water. If it sinks, you have too much water in the dropper. Take it out an release one or two drops of water. 5. Cut the balloon in half following the diagram. 6. Stretch the balloon to cover the mouth of the cylinder tightly and wrap the rubber band around the top to hold the balloon tightly in place. 7. Press on the balloon with your thumb. Watch the diver closely. Look at the water level in the diver. The diver should sink to the bottom of the cylinder. IF IT DOES NOT SINK, there is not enough water in the diver. Repeat steps 2-6, putting more water into the dropper. I've done the experiment so now I have to do the questions. 1. What happens to the air in the top of the graduated cylinder when you press on the balloon? When I press down on the top of the graduated cylinder, the air is pressed down as well. 2. What does this do to the water level in the diver? Why? The water in the diver seems to go up to the top of the medicine dropper. 3. What happens to the air in the diver when you press on the balloon? When I press on the balloon, the air in the diver appears to be going towards the bottom of the medicine dropper. 4. Why does the diver sink? The diver sinks because the volume of the air decreases. 5. This is a demonstration of "Boyle's Law" which relates pressure and volume. Fill in the blanks below: When air pressure increases, the volume of the air _______________. [decreases] When air pressure decreases, the volume of the air ______________. [increases] Could someone tell me if what I have now is right? I don't know the "why" part for number two and I don't think I have number four right (and/or explained all that well). If someone could explain it to me or give me a link, I would appreciate it.