States of Matter, and Phase Change Chapter 13 L

Liquids

Characteristics Density & Compression Fluidity Much denser then gases (and vapors) Compression requires large amounts of pressure Able to flow (mix with other liquids) Not as fluid as gases Because of intermolecular forces

Characteristics (….continued) Viscosity Surface tension Resistance to flowing Because they are closer together, attractions between them will resist movement Controlled by attractive forces Shape of molecules Temperature Measure of the inward pull of particles in the interior Greater attraction between particles, the higher the surface tension

Characteristics (….continued) Capillary action Cohesion – attraction between identical particles Adhesion – attraction between molecules that are different Together cause a liquid to move into the small spaces between other molecules Why if you drop a corner of toilet paper in the toilet, the whole sheet gets soaked

Solids

Characteristics Far denser then liquids or gases Molecules arranged in crystalline lattices Types of Crystalline Solids Type Unit particles Characteristics of solid phase Examples Atomic Atoms Soft to very soft; very low melting points, poor conductivity Group 8A elements Molecular Molecules Fairly soft; low to moderately high melting points; poor conductivity I2, H2O, NH3, CO2, C12H22O11 Covalent Network Atoms connected by covalent bonds Very hard; very high melting points; often poor conductivity Diamond (C), and quartz (SiO2) Ionic Ions Hard; brittle; high melting points; poor conductivity NaCl, KBr, CaCO3 Metallic Atoms surrounded by mobile valence electrons Soft to hard; low to very high melting points; malleable and ductile; excellent conductivity All metallic elements

Forces of attraction

Intermolecular forces forces between different molecules London forces (AKA dispersion forces) VERY weak attraction between non-polar covalent molecules Temporary dipole moment Electrons fly around the nucleus, therefore it is possible that any given moment they could cause a dipole to form Since electrons repel one another they can force this dipole on other atoms is only significant when molecules are very close Greatest between identical non-polar molecules

Induced Dipole moment

Intermolecular forces (….continued) Dipole-dipole forces Hydrogen Bonds Medium strength force between polar molecules Attraction is based on mass and polarity Smaller mass = more attraction Larger polarity = more attraction Strongest of intermolecular forces Attraction between H+ and O-2, F-1, N-3. When hydrogen is bound to any of those 3 it will be attracted to other molecules (+) H lines up with (-) cation Why water has such a high boiling point & surface tension

Phase changes

Phase change

Words and formulas Heat of Vaporization (DHvap): Heat required to vaporized 1 mole of a liquid Direct inverse of heat of condensation (DHvap = -DHcond) Heat of Fusion (DHfus) Heat required to melt 1 mole of a solid Direct inverse of heat of solidification (DHfus = -DHsolid)

Vapor Pressure Vaporization D of a liquid into gas Evaporation – vaporization of surface liquid As liquid becomes a vapor, it exerts a pressure on the surface of the liquid A substance boils when its vapor pressure is equal to or greater than atmospheric pressure DEMO!

Phase Change Diagram

Phase Change and Temp. While a substance it changing states there is NO change in T until all of the substance is in the next phase