Chem 101 Chapter 6

"How full of creative genius is the air in which these are generated! I should hardly admire them more if real stars fell and lodged on my coat." --Henry David Thoreau, 1856

Chapter 5 No attractive/repulsive forces in a gas

Question… How do snowflakes form?snowflakes

Two types of ‘bonding’ Chemical – –Results in very strong connection between atoms Secondary forces – – – –

Solids and Liquids NaCl – Water – Gasoline –

Compressibility – – – Volume change as state changes –1 mole water… Properties

What does that tell you about attractive forces between molecules in:

Phase Transitions Solid to liquid Liquid to solid Gas to solid

Heating Curve Temperature o C Energy added

Dipole-Dipole Occur between polar molecules

Ion-Dipole Occur between ions and molecules with a dipole Did salt dissolve in ethanol in the lab?

Hydrogen Bonding Results from large difference in electronegativity

London Dispersion Hexane – is it polar? Induced dipoles

H 2 Bond ONLY BETWEEN MOLECULES WITH H-F, H-O, and H-N

London Dispersion NONPOLAR MOLECULES ONLY BOND TO EACH OTHER THIS WAY

Predict Polarity… O 2 CH 2 F 2

Polarity and boiling See table 6.1 on page 152

Fractional Distillation

Review Which of the following can form hydrogen bonds ? – – – – –

Review Non Polar Molecules – Polar Molecules – H-bonding molecules –

Strength of Bonds LD<Dipole-Dipole<H-bond Surface Tension –

Soap Salt of a fatty acid –See page 158 Two ends – – –What type of bonding?

Solutions Why do some mixtures form solutions and others don’t? – – – Key is in the type of forces involved

Practice Are the following miscible? – –

Vaporization Defined – – –Just happens –Vapor – if the liquid and gas are both present

Dynamic Equilibrium Occurrence of two processes at the same time – Closed system

How do Secondary forces affect vapor pressure? High attraction – Low attraction – How does this affect boiling point?

Problem CH 3 OH and CH 3 I are both polar and the latter is much more massive. Why is methyl iodide’s vapor pressure at 22 o C almost 4 times greater than methyl alcohol?

Problem 2 Which has a higher boiling point and why? –

Review All gas laws, when and how to use them Pressure conversions Secondary forces –How they impact properties of substances –Their strength –Polarity –Vaporization –Why you sweat when you exercise –Heating curve