1. 3-3 Notes Part I

2. Section 3: The Behavior of Gases What types of measurements are useful when working with gases? How are the volume, temperature, and pressure of a gas related?

3. Measuring Gases When working with a gas, it is helpful to know its volume, temperature, and pressure. Let’s think back to chapter 1 and redefine some of these terms!

4. Volume Volume is the amount of space that matter fills. Since gas particles move to fill up the space available, the volume of a gas is the same as the volume of it’s container. Units for Volume = cm 3, mL, L, etc.

5. Temperature Temperature is a measure of the average energy of motion of the particles of matter. The faster the particles are moving, the more energy they have, and the higher the temperature they have. Units for temperature = K, °C, °F

6. Pressure Gas particles are constantly moving and pushing against the walls of their container. The pressure of the gas is the force of its outward push divided by the area of the walls of the container. Units for Pressure = pascals (Pa), or kilopascals (kPa). 1 kPa = 1,000 Pa

7. Pressure (continued) The firmness of a gas filled object comes from the pressure of the gas. Example: Air inside a fully pumped basketball has a higher pressure than the air outside, because there is a greater number of gas particles per unit volume inside the ball than in the air outside. Who knows what would happen if you poked a hole in the basketball?

8. A Change in Pressure A punctured basketball deflates as gas particles begin to escape. Due to high pressure inside the ball, gas particles hit the inner walls of the ball more often, therefore reach the hole more often and escape. The pressure inside drops until it equals the pressure outside.

9. Pressure and Volume If temperature is held constant, then gas pressure and volume are inversely proportional to each other. This means as one goes up, the other goes down. Example: If the volume is tripled, pressure would be 1/3 of what is was. This concept is described by Boyle’s Law.

10. Boyle’s Law Scientist Robert Boyle conducted experiments on air pumps to show that gas volume and pressure were related in the 1600s. Boyle’s law says that when the pressure of a gas at constant temperature is increased, the volume of the gas decreases. And when pressure decreases, volume increases.

11. Boyle’s Law As weights are added, the gas particles occupy a smaller volume. The pressure increases.

12. This is what a basic graph of Boyle’s Law should look like. It should show a nonlinear trend. At any point on the curve, you should be able to multiply the 2 variables and get the same product. 70 X 20 = 1400 50 X 28 = 1400 This is because the relationship between the 2 variables (Pressure and Volume) is that they are inversely proportional. Graphing Boyle’s Law: