Chemistry Chapter 13 Notes #1

States of Matter Be able to describe solid, liquid, and gases in terms of: – shape – volume – and particle arrangement!

States of Matter Solid –Definite shape –Definite volume –Particles are packed together tightly and cannot move past each other

States of Matter Liquid –Definite volume –No definite shape –Particles are close together, but can slide past each other

States of Matter Gas –No definite shape –No definite volume –Particles are VERY far apart from one another -volume of particles is Very small in comparison To volume of sample

Kinetic Molecular Theory Explains the properties of gases in terms of the energy, size, and motion of the particles –Size: small particles spread WAY out and there is no significant attraction between the particles –Motion – constant random motion – they move in straight lines until they collide –Energy – determined by mass and velocity KE = ½ mv 2 Temp is the measure of the average KE in matter

Behavior of Gases Gases have very low density (not very many particles in any given space) Gases can be compressed or expanded –How does compression and expansion affect density? Diffusion – when gases move from areas of high concentration to area of low concentration (due to random motion of particles) –Effusion – diffusion thru a small hole into a vacuum

Pressure Pressure = Force per unit area –Outside on a snowy day High heels v. tennis shoes v. snow shoes –Gases exert pressure on the walls of their container when they collide with the container –Barometer = instrument used to measure atmospheric pressure (commonly Hg) Increase in pressure = mercury rises Decrease – it drops Can be affected by altitude

Units of Pressure kPa, psi, mm Hg, torr, atm, etc… –Pascal (Pa) is the SI unit UnitCompared with 1atm Compared with 1kPa kPa 1 atm = kPa Mm Hg 1 atm= 760 mm Hg1 kPa = mm Hg Torr 1 atm= 760 torr1 kPa = torr Psi 1 atm= 14.7 psi1 kPa = psi atm 1 kPa = atm

Pressure Conversions 0.5 atm to kPa 300 kPa to atm 3.2 atm to psi 99 psi to atm

Dalton’s Law of Partial Pressures Total pressure of a mixture of gases is equal to the sum of the pressures of all the gases in the mixture

Example problems Find the total pressure of a mixture of gases that have partial pressures of 5.0kPa, 4.56 kPa, 3.02kPa, and 1.2 kPa. What is the partial pressure of H gas in a mixture of H and He if the total pressure is 600 mm Hg and the partial pressure of He is 439 mm Hg. Find the total pressure of the following mixture of gases (in atm) if the partial pressures are as follows: 6.2 atm, 3.1 atm, and 506 kPa.