Download Presentation
## GASES

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -

**Identify the abundances of the naturally occurring gases in**the atmosphere. • Describe the historical development of the measurement of pressure. • Describe the various units used to measure pressure.**Earth’s air is composed 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%**Torricelli (1608-1647) developed the first**• Barometer - measures air pressure • Height of mercury supported by atmospheric pressure at sea level is 760 mm.**Pascal (1623-1662) added to Torricelli’s “barometer.”**• Height affects the pressure of the atmosphere. Gay-Lussac(1778-1850) observed the law of combining volumes in chemical reactions. • Two volumes of hydrogen combined with one volume of oxygen to form two volumes of water. 2 H2 + O2 2 H2O**Gas/Vapour Pressure:**Pgas = Patm + h (greater than air) Pgas = Patm – h (less than air)**Dimensional Analysis**Problem-solving method using relationships to change units without changing value. Relationships are made by relating two things by their equivalent "amounts" as a ratio. • 1 filling OR 2 cookies • 2 cookies 1 filling**Dimensional Analysis (Converting Units):**Determine the unit ratio needed. Multiply the base unit by the unit ratio. (make sure you have the new unit on top) • 20 fillings = ? cookies • 1 fillings OR 2 cookies • 2 cookies 1 filling • 20 fillings x2 cookies = 40 cookies • 1 fillings**2. 3 m = ? cm**• 1 m or100 cm • 100 cm 1 m • 3 m x100 cm = 300 cm • 1 m**3. 5 kL = ? mL**• *need to multiply by TWO factors: • kL L mL • 1 kLand 1 L • 1000 L 1000 mL • 5 kLx1000 L x 1000 mL = 5 000 000 mL • 1 kL 1 L**1. atmosphere (atm):**• 1 atm = 760 mmHg = 101.325 kPa • 2. Pascal (Pa) – standard international (SI) units. • Defined as 1 Newton of force per m2. • Use kiloPascals. • 3. Millimetres of mercury (mmHg) – not common. • 4. Pounds per square inch (psi) - Imperial • 1 kPa is equal to 0.145 psi 1 atm is equal to 14.7 psi.**What is the pressure of the gas in kPa?**Pgas = 762 mm + 15 mm = 777 mmHg • 777 mmHg x101.3 kPa = 103.6 kPa • 760 mmHg**Gas pressure is due to the force of gaseous particles**colliding with their container. • Torricelli invented the barometer to measure atmospheric pressure. • Units used: mmHg, atm, kPa, psi • Using a manometer: • gas pressure > air pressure Pgas = Patm + h • gas pressure < air pressure Pgas = Patm – h.