Opening: Hot and Cold Balloons Maria filled a balloon with air. She tightly tied the balloon so no air could get in or out of the balloon. She kept the balloon in a warm room. An hour later she put the balloon in a sold freezer. When she tool the balloon out 30 minutes later, it was still tied tightly shut. No air escaped form the balloon; however, the balloon had shrunk. Maria wondered if the mass of the balloon (including the air inside it) also changed. Choose the answer that best matches your thinking. Write your claim, evidence, and reasoning.

A.The mass of the warm balloon is less than the mass of the cold balloon. B. The mass of the warm balloon is greater than the mass of the cold balloon. C. The mass of the warm balloon is the same as the mass of the cold balloon.

GPS and EQ Primary Standard and Element: SPS5. Students will compare and contrast the phases of matter as they relate to atomic and molecular motion. b. Relate temperature, pressure, and volume of gases to the behavior of gases. Supporting Element: a. Compare and contrast the atomic/molecular motion of solids, liquids, gases and plasmas. EQ What are the principles of Boyle’s Law and Charles’ Law?

Opening thoughts… Have you ever: Seen a hot air balloon? Had a soda bottle spray all over you? Baked (or eaten) a nice, fluffy cake? These are all examples of gases at work! NEXTPREVIOUS MAIN MENU

Properties of Gases You can predict the behavior of gases based on the following properties: NEXTPREVIOUS MAIN MENU Pressure Volume Amount (moles) Temperature Lets review each of these briefly…

NEXTPREVIOUS MAIN MENU Pressure Volume Amount (moles) Temperature You can predict the behavior of gases based on the following properties:

Pressure Pressure is defined as the force the gas exerts on a given area of the container in which it is contained. The SI unit for pressure is the Pascal, Pa. If you’ve ever inflated a tire, you’ve probably made a pressure measurement in pounds (force) per square inch (area). NEXTPREVIOUS MAIN MENU

NEXTPREVIOUS MAIN MENU Pressure Volume Amount (moles) Temperature You can predict the behavior of gases based on the following properties:

Volume Volume is the three-dimensional space inside the container holding the gas. The SI unit for volume is the cubic meter, m 3. A more common and convenient unit is the liter, L. Think of a 2-liter bottle of soda to get an idea of how big a liter is. (OK, how big two of them are…) NEXTPREVIOUS MAIN MENU

NEXTPREVIOUS MAIN MENU Pressure Volume Amount (moles) Temperature You can predict the behavior of gases based on the following properties:

Temperature Temperature is the measurement of heat…or how fast the particles are moving. Gases, at room temperature, have a lower boiling point than things that are liquid or solid at the same temperature. Remember: Not all substance freeze, melt or evaporate at the same temperature. NEXTPREVIOUS MAIN MENU Water will freeze at zero degrees Celsius. However Alcohol will not freeze at this temperature.

How do they all relate? Some relationships of gases may be easy to predict. Some are more subtle. Now that we understand the factors that affect the behavior of gases, we will study how those factors interact. NEXTPREVIOUS MAIN MENU

Boyle’s Law Boyle’s Law – at constant temperature, the volume of the gas increases as the pressure decreases. The volume of the gas decreases and the pressure increases. P 1 V 1 = P 2 V 2 V ↑ P↓ VolumeLVolumeL Pressure (kPa) If you squeeze a gas sample, you make its volume smaller.

Moveable piston ↕ Now... a container where the volume can change (syringe) Same temperature Volume is 100 mL at 25 °C Volume is 50 mL at 25 °C In which system is the pressure higher? (Which has the greater number of collisions with the walls and each other?)

Boyle’s Law at Work… Doubling the pressure reduces the volume by half. Conversely, when the volume doubles, the pressure decreases by half.

Charles’ Law Charles’ Law – at a constant pressure, the volume of a gas increases as the temperature of the gas increases and the volume decreases when the temperature decreases. VolumeLVolumeL Temperature (K) V 1 V 2 T 1 T 2 = increase AKE increase the speed of the particles the walls of a flexible container expand – think of hot air balloons!

Steel cylinder (2L) contains 500 molecules of O 2 at 400 K Steel cylinder (2L) contains 500 molecules of O 2 at 400 K Steel cylinder (2L) contains 500 molecules of O 2 at 800 K 1.In which system do the O 2 molecules have the highest average kinetic energy? 2.In which system will the particles collide with the container walls with the greatest force? 3.In which system is the pressure higher? B B B

Charles’ Law at Work… As the temperature increases, the volume increases. Conversely, when the temperature decreases, volume decreases. NEXTPREVIOUS MAIN MENU

How Can I Remember These Gas Laws? Easy! Take a piece of paper and fold it.

Label Your Paper P TV

If T is Constant, put your finger on it and turn the paper diagonal (both ways) P TV When you turn your paper, P increases V decreases or visa versa. Which law is this?

Now Pressure is Constant. Move the Paper Diagonal in Both Directions. P TV What did you discover? Which law is this?

I Can Read Your Mind! But I am not telling! For extra credit, what happens when V remains constant? What Gas Law is this? Answer these 2 questions for bonus points on your next summative assessment!