Obtain a large, plastic syringe and draw 25 mL of water into it. Eliminate any bubbles of air. Place the opening of the syringe securely against a rubber stopper or cork. Push down on the plunger of the syringe without allowing water to leak from the syringe. Describe how the volume of the water changes with an increase in pressure. Repeat the above procedure using 25 mL or air. How does the volume of air change with an increase in pressure? Try to explain the reason for any differences you may have observed The properly you have just investigated is called compressibility. What must be happening to particles when a material is compressed? Think about walking in knee deep water, or moving your legs while lying in a bath tub filled with water. Now think about walking in air. Which is easier and why? Water has a density of about 1g/mL at room conditions. Each air molecule has approximately 10 diameters in each direction (x, y, and z). Estimate the density of air at room conditions. The density of a gas depends on its molar mass. Under the same conditions, gases with molar masses less than air will float, while those with molar masses greater than the molar mass of air will sink in air. Air has the equivalent of a molar mass of 29 g/mole. How do you think that value was obtained?