Title: The Properties of Gases and the Laws that govern them.
9th - 12th Grade High School Chemistry
Principles(s) Investigated: This set of demonstrations is designed to help the students understand the properties of gases and the laws that govern them. Students will first observe the properties of gases, collect data and come to a conclusion based those observations. Students will then observe the effects of pressure and temperature on the volume of gases, collect data and come to a conclusion based on those observations.
California State Content Standards: Chemistry
4a. Students know the random motion of molecules and their collisions with a surface create the observable pressure on that surface.
4b. Students know the random motion of molecules explains the diffusion of gases.
4c. Students know how to apply the gas laws to relations between the pressure, temperature, and volume of any amount of an ideal gas or any mixture of ideal gases.
4g. Students know the kinetic theory of gases relates the absolute temperature of a gas to the average kinetic energy of its molecules or atoms.
Materials: Smoke Diffusion Unit (Procedure to make below), Lighter, Fume Hood, Balloons, Vacuum Chamber, Vacuum Pump, Beaker, Ring Stand, Rubber Band, Acetone, Dry Ice, Pyrex Dish, Hot Plate, Stir Bar, KNO3, Sugar.
Creation of Smoke Diffusion Unit
1. Weigh out 50 grams KNO3 along with 30 grams sugar. Mix and grind these two items using the mortar and pestle.
2. Turn on your hot plates to a medium high setting. Pour the KNO3 and sugar mixture into a beaker. Place the beaker on the plate and stir using the glass stirring rod.
3. Remove from heat once mixture is liquefied.
4. Create a case for the liquid using aluminum foil, pour mixture in aluminum foil case, and allow cooling down for 24 hours.
Demonstration – Observation of Smoke Diffusion Unit
1. Place smoke diffusion unit in fume hood on top of a fire proof surface.
2. Ignite smoke diffusion unit and close fume hood.
3. Observe and collect data from students.
4. Analyze data with students.
Demonstration – The effects of Pressure on Volume
1. Blow up a balloon and place in vacuum chamber.
2. Turn on vacuum pump.
3. Observe and have students collect data.
4. Reintroduce air into vacuum chamber.
5. Observe and have students collect data.
6. Do data analysis of data with students.
Demonstration – The effects of Temperature on Volume
1. Place dry ice in a Pyrex beaker, add acetone slowly and allow mixture to reach ~ -78°C.
2. Blow up balloon and attach to ring stand using a rubber band, place a Pyrex dish under the setup.
3. Slowly pour the acetone dry ice mixture over the balloon.
4. Observe and have students collect data.
5. Observe what happens to the volume as the acetone evaporates off and have students collect data.
Student Prior Knowledge: Students know (1) conservation of matter, (2) types of phases, (3) phase changes, (4) kinetic molecular theory.
Explanation: Gases behave a certain way and kinetic molecular theory explains why these gases behave this way. The first demonstration shows the observable physical properties of a gas, which correlates to kinetic molecular theory. The next gas laws to be observed are Boyle’s and Charles’ Law, which also correlates to kinetic molecular theory.
Applications to Everyday Life:
1. Safety issues such as in never heat a closed container come to mind when learning about gases, as well as implosions. This is due to the kinetic energy of the gas molecules and kinetic molecular theory explains this phenomenon.
2. Another application to life is how gases move. In the event of a serious chemical hazard and a toxic gas cloud looms overhead. We can use the kinetic molecular theory to best protect us from this hazard.