c. Because gas molecules are far apart, the mass present in 1 mL of a gas is very small. The mass of a gas present in 1L is on the same order of magnitude as the mass of a liquid present in 1mL 3. Consider two people of the same mass standing in a room. One person is standing normally, and the other is standing on one foot. A. Does one person exert a greater force on the floor than the other? B. Does one person exert a greater pressure on the floor than the other? a. F= ma; Since both people have the same mass and both experience the acceleration of gravity, the forces they exert on the floor are exactly equal. b. P = F/A; The two forces are equal, but the person standing on one foot exerts this force over a smaller area. Thus, the person standing on one foot exerts a greater pressure on the floor.
4. Rationalize the following observations: a. Aerosol cans will explode if heated Heating the can will increase the pressure of the gas inside the can, P α T, V and n constant. As the pressure increases, it may be enough to rupture the can. b. You can drink through a soda straw As you draw a vacuum in your mouth, atmospheric pressure pushing on the surface of the liquid forces the liquid up the straw. c. A thin-walled can will collapse when the air inside is removed by a vacuum pump The external atmospheric pressure pushes on the can. Since there is no opposing pressure from the air inside, the can collapses. d. Manufacturers produce different types of tennis balls for high and low elevations. How “hard” the tennis ball is depends on the difference between the pressure of the air inside the tennis ball and atmospheric pressure. A “sealevel” ball will
- Summer '08