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 isVery 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 mv2

• 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

Unit Compared with 1atm

Compared with 1kPa

kPa 1 atm = 101.3 kPa

Mm Hg 1 atm= 760 mm Hg 1 kPa = 7.501 mm Hg

Torr 1 atm= 760 torr 1 kPa = 7.501 torr

Psi 1 atm= 14.7 psi 1 kPa = 0.145 psi

atm 1 kPa = 0.009869 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.