We did this experiment to understand how air pressure works as part of our lessons on birds and how they are able to fly (Apology - Zoology 1 textbook). I created some free worksheets based on the Scientific Method to use with this experiment.
* 1 clear glass or plastic cup
* 1 Plastic straw
* Scotch tape
1. Tape the straw to the inside of the glass.
2. Cut the straw about 1/2 inch above the rim of the glass.
3. Fill the glass to the top with water.
1. Document your hypothesis on the worksheet.
2. Use the remaining part of the straw to blow air at an upward angle above the straw in the glass.
5. Be sure not to blow above the water, but rather upwards above the vertical straw.
The area where air is blown above the vertical straw becomes an area of low pressure. Since the air above the water is not moving, it continues to press down on the water in the glass. This air above the water in the glass presses down harder than the air in and above the straw. As a result the water is forced up and out of the straw.
Below is a close-up of the water shooting out of the glass. You can see that the surface of the water in the glass remains undisturbed.
Source: Apologia - Exploring Creation with Zoology 1