AssignmentAssignment b Complete pre-assessment test. b Read Chapter 10, pp , and define vocabulary.

Learning Log Write down at least 5 things you know about gases.

Gases are a part of our everyday life

I. Physical Properties (p ) Ch. 10 & 11 - Gases

Kinetic-Molecular Theory b States that the particles of matter are always in motion. b 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 b Ideal gas – an imaginary gas that perfectly fits all the assumptions of the kinetic-molecular theory b (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 mv 2 all gases at same temp have same KE lighter gases have higher speeds than heavier gases

B. KMT and the Nature of Gases b Expansion – gases expand to fill any container. random motion, no attraction b Fluidity -gases are fluids (like liquids). no attraction b Low density - gases have very low densities. (1/1000) lots of empty space, particles far apart

B. KMT and the Nature of Gases b Compressibility – gases can be compressed. lots of empty space, particles far apart b Diffusion and effusion – gases undergo diffusion & effusion. random motion, low mass gases faster

C. Real Gases b Real gas – does not behave completely according to the assumptions of the kinetic- molecular theory b Particles in a REAL gas… have their own volume attract each other

C. Real Gases b 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 b Barometer measures atmospheric pressure b Manometer measures contained gas pressure

D. Pressure b KEY UNITS AT SEA LEVEL kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi

E. STP Standard Temperature & Pressure 0°C 273 K 1 atm kPa -OR- STP

F. Temperature ºF ºC K K = ºC b Always use absolute temperature (Kelvin) when working with gases.

Practice Problems - Pressure b The average atmospheric pressure in Denver, Colorado, is atm. Express this pressure (a) in mm Hg and (b) in kPa. (a) atm x 760 mm Hg = 631 mm Hg 1atm (b) atm x kPa = 84.1 kPa 1atm

Practice Problems - Temperature b Convert -273°C to Kelvin temperature = 0 K b Convert 20 K to Celsius temperature. 20 – 273 = -253°C

Homework Assignment b Complete #17-19 on p. 327 of the textbook.