GASES

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

“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 0 - 4% Oxygen 20.9% Carbon Dioxide 0.035% Argon 0.9% Methane 0.0002% Neon 0.002% Ozone 0.000004% Helium 0.0005% Krypton 0.0001% Hydrogen 0.00005% “Variable” gases change with seasons, pollution levels, location…

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 (1608-1647) 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 (1623-1662) Recognized that height affects atmospheric pressure. Air pressure is less up a mountain – even gas molecules are subject to the effects of gravity

Connect this back to molar volume… Key Moments in the Understanding of Pressure and Specifically Air Pressure: 3. Huygens (1629-1695) Invented the manometer. Compares pressure of a gas against the atmospheric pressure by seeing which way the mercury rises 4. Gay-Lussac (1778-1850) Recognized the Law of Combining Volumes 2 H2 + 1 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…

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

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 = 760 mmHg = 101.325 kPa = 14.7 psi

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

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 = 0.58 atm 14.7 psi 1 atm = 760 mmHg = 101.325 kPa = 14.7 psi

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 = 103.6 kPa 760 mmHg 1 atm = 760 mmHg = 101.325 kPa = 14.7 psi

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