3.2 The Gas Laws
Reading Focus
Key Concepts
What causes gas pressure in a closed container?- What factors affect gas pressure?
- How are the temperature, volume, and pressure of a gas related?
Vocabulary
pressure
absolute zero
Charles's law
Boyle's law
Reading Strategy
Identifying Cause and Effect Copy the diagram. As you read, identify the variables that affect gas pressure.
The woman in Figure 10 is taking a deep breath. This action helps reduce her breathing rate and increase the volume of air she inhales. When you inhale, the volume of your chest cavity increases and air moves into your lungs. When you exhale, the volume of your chest cavity decreases and air is pushed out of your lungs.
After you read this section, you will understand how changing the volume of your chest cavity causes air to move into and out of your lungs. Changes in the volume, the temperature, the pressure, and the number of particles have predictable effects on the behavior of a gas.
Pressure
At many hockey rinks, a layer of shatterproof glass keeps the puck away from the spectators. The force with which the puck hits the glass depends on the speed of the puck. The faster the puck is traveling, the greater the force is. The smaller the area of impact is, the greater the pressure produced. Pressure is the result of a force distributed over an area. If the edge of the puck hits the glass, it exerts more pressure than if the face of the puck hits the glass at the same speed.
The SI unit of pressure is derived from SI units for force and area. Force is measured in newtons (N) and area in square meters (m2). When a force in newtons is divided by an area in square meters, the unit of pressure is newtons per square meter (N/m2). The SI unit for pressure, the pascal (Pa), is shorthand for newtons per square meter. One pascal is a small amount of pressure. Scientists often express larger amounts of pressure in kilopascals. One kilopascal (kPa) is equal to 1000 pascals.
Figure 10 Taking a deep breath increases the volume of your chest cavity, which causes air to move into your lungs.
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