chem Chapter 8

What is a phase?

a form of matter with a specific set of physical properties

solid phase description

particles in contact, held in place

liquid phase description

particles in contact but moving past each other

gas phase description

particles far apart, moving freely

melting vs. freezing

melting = solid → liquid ( +heat)

freezing = liquid → (-heat)

vaporization vs. condensation

vaporization = liquid → gas ( +heat)

condensation = gas → (-heat)

sublimation vs. deposition

sublimation = solid → gas

deposition = gas → solid

What determines melting/boiling point?

strength of intermolecular interactions

what happens to KE during melting/boiling?

KE increases

heat is added

what happens to KE during freezing/condensing?

KE decreases

heat is removed

What determines whether a substance is solid, liquid, or gas?

balance between kinetic energy and intermolecular forces

what are dispersion forces?

temporary dispoles in non-polar molecules

when do dispersion forces increase?

with larger, more polarizable electron clouds

what are dipole-dipole attractions?

Attractions between polar molecules

Requirements for hydrogen bonding

• H bonded to F, O, or N

• a lone pair on F, O, or N

What are hydrogen bonds important?

• strongest molecular force

• stabilize DNA and proteins

What are ionic interactions?

attractions between full + and - charges

Weakest forces → lowest melting points

dispersion forces

Strongest forces → highest melting points

ionic compounds

Which elements exist as gases at room temp?

• H₂

• N₂

• O₂

• F₂

• Cl₂

• noble gases

Which nonmetal oxides are gases?

• CO

• CO₂

• NO

• NO₂

• SO₂

• SO₃

5 assumptions of Kinetic Molecular Theory ( KMT)

1. particles more randomly, fast

2. no significant attractions

3. volume of particles « container

4. constant straight - line motion

5. temperature = average KE

4 variables describing gases

1. pressure : P

2. Volume : V

3. temperature : T

4. amount : n

Units of pressure

• atm

• mmHG

• Torr

• Pa

• psi

1 atm = what?

760 mmHg = 760 Torr

statement of charles’s law

Volume/temp. is a constant

Charles Law equation

V₁/T₁ = V₂/T₂

Temp. Requirement

must use kelvin

what happens to atmospheric pressure with altitude?

pressure decreases as altitude increases

What does a barometer measure?

Atmospheric pressure in mmHg

Inhalation (Boyle’s Law)

• Lung volume increases

• pressure decreases

• air flows in

Exhalation ( Boyle’s law)

• lung volume decreases

• pressure increases

• air flows out