I. Physical Properties (p. 303 - 312) Ch. 10 & 11 - Gases I. Physical Properties (p. 303 - 312)

The Kinetic-Molecular Theory of Matter Used to explain the properties of gases, liquids and solids in terms of: 1) Energy of particles 2) Forces acting between particles. Kinetic Theory is based on the idea that particles of matter are in constant motion and that this motion has consequences.

The Kinetic-Molecular Theory of Gases Ideal Gas - Imaginary gas that conforms perfectly to all assumptions of the Kinetic Theory.

A. Kinetic Molecular Theory Particles in an ideal gas… have no volume. have elastic collisions. are in constant, random, straight-line motion. don’t attract or repel each other. have an avg. KE directly related to Kelvin temperature.

B. Real Gases Particles in a REAL gas… have their own volume attract each other, therefore collisions are not elastic (slowed down) Avg KE still directly related to Kelvin Temp

Real gas Gas behavior is most ideal… at low pressures at high temperatures in nonpolar atoms/molecules

The Kinetic Theory and the Nature of Gases The Kinetic Theory accounts for the following physical properties of gases: Expansion - gases do not have a definite shape nor definite volume, they fill the container they are in. Fluidity - There is very little attraction between gaseous particles, they flow past each other. Low Density - Most of a gas is empty space. The same amount of a gas as a liquid/solid takes up 100% more space.

Compressibility - because there is so much space between molecules in a gas they can be crowded closer together. Diffusion - spontaneous mixing of 2 substances due to random motion. A) Rate of Diffusion - depends upon 1) speed of molecules 2) size 3) attractive forces Effusion gas particles under pressure pass through a very small hole from one container to another. A) Rate of Effusion - is directly proportional to the velocity of the particles.

C. Characteristics of Gases Gases expand to fill any container. random motion, no attraction Gases are fluids (like liquids). no attraction Gases have very low densities. no volume = lots of empty space

C. Characteristics of Gases Gases can be compressed. no volume = lots of empty space Gases undergo diffusion & effusion. random motion

10.2 Qualitative Description of Gases To describe gases accurately, you must use 4 measureable quantities; 1. Temperature 2. Pressure 3. Volume 4. Quantity or # of Particles

Temperature Scales a) Celsius - developed by Anders Celsius(1701-1744) - 0oC freezing pt. of water - 37oC body temperature - 100oC boiling pt. of water - 20oC normal room temperature b) Fahrenheit - developed by inventor of Mercury thermometer - Gabriel Daniel Fahrenheit in 1714. - 32oF freezing pt. of water - 98.6oF body temperature - 212o F boiling pt. of water c) Kelvin - developed by William Thomson, Lord Kelvin. - K, Kelvin is the SI unit of Temperature - 0 K, Zero Kelvin - Absolute Zero - 273 K freezing pt. of water - 373 K boiling pt. of water

D. Temperature Always use absolute temperature (Kelvin) when working with gases. ºF ºC K -459 32 212 -273 100 273 373 K = ºC + 273

E. Pressure Which shoes create the most pressure?

E. Pressure Barometer measures atmospheric pressure Aneroid Barometer Mercury Barometer Aneroid Barometer

E. Pressure Manometer measures contained gas pressure U-tube Manometer Bourdon-tube gauge

E. Pressure KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm = 30 in. Hg 760 mm Hg 760 torr 14.7 psi

VOLUME Volume- amount of space an object takes up Solid – L x W x H, cm3 Fluid(Gas/Liquid) -- Graduated Cylinder in ml Quantity/# of Particles – measured in moles(6.022 x 1023 particles)

Standard Temperature & Pressure F. STP STP Standard Temperature & Pressure 0°C 273 K 1 atm 760 mm -OR-