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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. Gases are a part of our everyday life. Ch. 10 & 11 - Gases. I. Physical Properties (p. 303 - 312). Kinetic-Molecular Theory.
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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.