Understanding Gases: Properties, Kinetic-Molecular Theory, and Real Gas Behavior
This assignment requires students to complete a pre-assessment test and study Chapter 10 of the textbook focusing on gases. Students will explore the Kinetic-Molecular Theory (KMT), which explains gas behavior based on particle motion and energy. Key concepts include the characteristics of ideal and real gases, pressure measurements, and calculations related to temperature in Kelvin. Students should document their prior knowledge of gases and complete practice problems related to pressure and temperature conversions by the end of the assignment.
Understanding Gases: Properties, Kinetic-Molecular Theory, and Real Gas Behavior
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Assignment • Complete pre-assessment test. • Read Chapter 10, pp.302-325, and define vocabulary.
Learning Log Write down at least 5 things you know about gases.
Ch. 10 & 11 - Gases I. Physical Properties(p. 303 - 312)
Kinetic-Molecular Theory • States that the particles of matter are always in motion. • Can be used to explain the properties of solids, liquids and gases based on the energy of particles and the forces that act between them.
A. Kinetic-Molecular Theory of Gases • Ideal gas – an imaginary gas that perfectly fits all the assumptions of the kinetic-molecular theory • (5) Assumptions - Particles in an ideal gas • 1. Are very far apart - gases are mostly empty space • 2. Have elastic collisions.
A. Kinetic-Molecular Theory of Gases • 3. are in constant, random, straight-line motion. • 4. don’t attract or repel each other. • 5. have an avg. KE directly related to Kelvin temperature. KE = ½ mv2 all gases at same temp have same KE lighter gases have higher speeds than heavier gases
B. KMT and the Nature of Gases • Expansion – gases expand to fill any container. • random motion, no attraction • Fluidity -gases are fluids (like liquids). • no attraction • Low density - gases have very low densities. (1/1000) • lots of empty space, particles far apart
B. KMT and the Nature of Gases • Compressibility – gases can be compressed. • lots of empty space, particles far apart • Diffusion and effusion – gases undergo diffusion & effusion. • random motion, low mass gases faster
C. Real Gases • Real gas – does not behave completely according to the assumptions of the kinetic-molecular theory • Particles in a REAL gas… • have their own volume • attract each other
C. Real Gases • Gas behavior is most ideal… • at low pressures • at high temperatures • in nonpolar atoms/molecules
D. Pressure Which shoes create the most pressure?
D. Pressure • Barometer • measures atmospheric pressure • Manometer • measures contained gas pressure
D. Pressure • KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi
E. STP Standard Temperature & Pressure 0°C273 K 1 atm101.325 kPa -OR- STP
F. Temperature K = ºC + 273 ºF -459 32 212 ºC -273 0 100 K 0 273 373 • Always use absolute temperature (Kelvin) when working with gases.
Practice Problems - Pressure • The average atmospheric pressure in Denver, Colorado, is 0.830 atm. Express this pressure (a) in mm Hg and (b) in kPa. (a) 0.830 atm x 760 mm Hg = 631 mm Hg 1atm (b) 0.830 atm x 101.325 kPa = 84.1 kPa 1atm
Practice Problems - Temperature • Convert -273°C to Kelvin temperature. -273 + 273 = 0 K • Convert 20 K to Celsius temperature. 20 – 273 = -253°C
Homework Assignment • Complete #17-19 on p. 327 of the textbook.
