1. GASES

2. OUTCOME QUESTION(S): C11-2-07 UNITS AND RELATIONSHIPS
Describe the various units used to measure pressure and convert between units.
Include: atmospheres, kilopascals, millimetres of mercury
Experiment to develop the relationship between the pressure and volume of a gas using visual, numeric, and graphical representations.
Include: Boyle’s Law
Experiment to develop the relationship between the volume and temperature of a gas using visual, numeric, and graphical representations.
Include: Charles’ Law, Absolute zero, Kelvin scale, Ideal gas
Develop the relationship between the pressure and temperature of a gas using visual, numeric, and graphical representations.
Include: Gay-Lussac’s Law, Dalton’s Law
Vocabulary & Concepts 
Barometer Manometer

3. “Variable” gases change with seasons, pollution levels, location…
The composition of Earth’s air has changed over geologic time – it is currently a homogenous mixture of two types of gases:
Permanent Variable____________
Nitrogen 78.1% Water vapor % Oxygen 20.9% Carbon Dioxide 0.035%
Argon 0.9% Methane % Neon 0.002% Ozone % Helium % Krypton % Hydrogen %
“Variable” gases change with seasons, pollution levels, location…

4. Worst title for a slide ever…
Key Moments in the Understanding of Pressure and Specifically Air Pressure:
Worst title for a slide ever…
1. Torricelli ( ) Invented the barometer.
Measures air pressure by how high the mercury is forced up the column
Standard height of mercury supported by air pressure at sea level is 760mm
Pascal ( ) Recognized that
height affects atmospheric pressure.
Air pressure is less up a mountain – even gas molecules are subject to the effects of gravity

5. Connect this back to molar volume…
Key Moments in the Understanding of Pressure and Specifically Air Pressure:
3. Huygens ( ) Invented the manometer.
Compares pressure of a gas against the atmospheric pressure by seeing which way the mercury rises
4. Gay-Lussac ( )
Recognized the
Law of Combining Volumes
2 H O2  2 H2O
Two volumes of hydrogen combined with one volume of oxygen to form two volumes of water.
Connect this back to molar volume…

6. Pgas = Patm + h (gas pressure is greater than air)
stronger
stronger
Pgas = Patm + h (gas pressure is greater than air)
Pgas = Patm – h (gas pressure is less than air)
The height of the movement of mercury is added/subtracted to the known air pressure to find the pressure of the gas

7. Notable Units of Pressure
Pascal (Pa) - Standard International (SI) Unit
Defined as 1 Newton of force per m2
Typically utilized as kiloPascals (kPa)
Atmosphere (atm)
Represents mean air pressure at sea level (1 atm)
Millimetres of mercury (mmHg)
Not as commonly used (but historically important…)
Pounds per square inch (psi)
Imperial units (American)
1 atm = mmHg = kPa = psi

8. Rules for Dimensional Analysis
Start with what you know
Identify (or create) the conversion factor
Put units you want to cancel on bottom
Put units you need on the top
Multiply across top, divide across bottom
Dimensional Analysis is a way to convert units:
(make the value the same but in different units)
Some people simplify this notation with added bars – called “factor label line”
How many pizzas would 250 pieces of pepperoni make?
1 pizza
250 pepperoni
= 13.2 Pizzas
19 pepperoni

9. An American soccer ball needs to be inflated to
8.5 psi. What is this in mmHg and atm?
8.5 psi
760 mmHg
= 440 kPa
14.7 psi
8.5 psi
1 atm
= atm
14.7 psi
1 atm = mmHg = kPa = psi

10. What is the pressure of this gas in kPa?
Pgas > Patm
Pgas = Patm + h
Pgas = 762 mm + 15 mm = 777 mmHg
stronger
777 mmHg
101.3 kPa
= kPa
760 mmHg
1 atm = mmHg = kPa = psi

11. CAN YOU / HAVE YOU? C11-2-07 UNITS AND RELATIONSHIPS
Describe the various units used to measure pressure and convert between units.
Include: atmospheres, kilopascals, millimetres of mercury
Experiment to develop the relationship between the pressure and volume of a gas using visual, numeric, and graphical representations.
Include: Boyle’s Law
Experiment to develop the relationship between the volume and temperature of a gas using visual, numeric, and graphical representations.
Include: Charles’ Law, Absolute zero, Kelvin scale, Ideal gas
Develop the relationship between the pressure and temperature of a gas using visual, numeric, and graphical representations.
Include: Gay-Lussac’s Law, Dalton’s Law
Vocabulary & Concepts 
Barometer Manometer