Ch 11 Gas Pressure
Objectives:
1. Model the effects of changing the number of particles, mass, temperature, pressure, and volume on a gas using the kinetic theory of matter
- Pressure is directly proportional to the number of particles
- The greater the mass, the more air particles and therefore, the greater the pressure.
- Pressure is directly proportional the temperature, if the volume and the number of particles remains the same
- Pressure is indirectly proportional to the volume if the temperature and number of molecules remains constant.
2. Measure atmospheric pressure
Be able to explain how a barometer works ** see handout Torricelli’s experiment
Know units for standard temperature and pressure (STP)
3. Demonstrate the ability to use the factor label method to convert pressure units
Table of Equivalent pressures
1.00 atm 760 mm Hg 14.7 psi 101.3 kPa
examples:
Practice problems:
3800 mm Hg –> ____? psi
506.5 kPa –> ____? atm
10 atm –> ____? mm Hg
Vocabulary:
Pressure
Barometer
Standard temperature and pressure (STP)
Pascal (Pa)
Kilopascal (kPa)
Factor label method
Activities:
Lab page 375
- Complete questions 3 and 4 from the text.
- Complete graph mass vs volume with given data.
- What is the relationship between the volume and the mass of a gas? Explain.
- Did the mass of the sealed bag containing the dry ice change as the dry ice sublimed? Why?
Demonstrations:
Demo 1
Three candles of different heights are placed in an aquarium. Dry ice is added to the bottom of the aquarium.
What will happen to the three candles? Explain.
What can you infer about the density of carbon dioxide compared to the air in the classroom?
What evidence from the demonstration supports this?
Demo 2
Two students selected from the class pour water into funnels resting on top of flasks.
Were both students successful?
What are some possible reasons why one student cannot pour the water into the flask?
Ch 11.2 The Gas Laws
Part 1 Boyle’s Law
Boyle’s Law states that the pressure and volume of a gas at constant tempertaure are inversely proportional.
P1V1 = P2V2 ** the pressure x volume before = pressure x volume after
Here is a link showing Boyle’s experiment
Boyle had 4 findings from his experiment
- If the pressure of a gas increases, its volume decreases proportionally
- If the pressure of a gas decreases, its volume increases proportionally
- If the volume of a gas increases, its pressure decreases proportionally
- If the volume of gas decreases, its pressure increases proportionally