Forces of Attraction, Liquids, Solids, & Phase Diagrams

Forces of Attraction(13-2)A. Intramolecular forces – within molecules

B. Intermolecular Forces– attractions between particles(three types) 1. Dispersion Forces – found in all particles/more in larger

particles2. Dipole – found in polar particles3. Hydrogen Bonds – found in polar particles with H bonded

to a “FON” element

C. Greater attractive forces between their particles give substances higher melting/boiling points (i.e. why F2 and Cl2 are gases, Br2 is a liquid and I2 is a solid)

Liquids (13-3)A. Surface tension – tendency of a liquid to “hold itself

together” (minimize surface area) — this is due to IM forces (COHESION)

B. Capillary action – movement of liquids up small diameter tubes• cohesive forces – IM forces• adhesive forces – attractive forces between the molecules

and a surface or containerC. Viscosity • measure of a liquids resistance to flow (syrup has a

higher viscosity than water) • substances with large IM forces tend to be highly viscous

Figure 4: It is possible to see that in water, the strength of the cohesion forces are larger than the strength of the adhesion forces. This results in the concave formation of water in the capillary tube. This is known as capillary attraction. Alternatively, the adhesion forces are evidently stronger than the cohesion forces which allows the mercury to bend in a convex formation away from the walls of the capillary tube. This is known as capillary repulsion.

Capillary Action

Viscosity

Solids (13-3)A. Density of solids –depends on the substanceB. Types of solids

1. Crystalline– They have a regular structure, in which the particles pack in a repeating pattern from one edge of

the solid to the other.

a. Ionic (ex: ??)b. Molecular (ex: ??) c. Atomic

–Covalent network (ex: ??)–Metallic (ex: ??)–Noble gases (ex: ??)

2. Amorphous (ex: ??) – literally, "solids without form") have a random structure, with little if any long-range order.

Diamond

Salt

sugar (C12H22O11)

Copper

Wax

(Ne, Ar, Kr, and Xe) at negative pressure and temperatures below the triple-point temperature

Phase Diagrams (13-4)A. Water’s versus carbon dioxide’s B. Shows three phases as they exist at

different pressure and temperature values (y and x axes)

C. Lines represent equilibrium between phases (or phase changes) Which are endothermic / exothermic?

D. Triple point – equilibrium between all three phases (“boiling ice water”)

Vapor Pressure (13-4)A. the tendency of particles in the liquid phase

to enter the gas phase at that temperatureB. open system–continuous evaporation/closed

system–equilibriumC. VP increases with increasing temp.D. a liquid boils when VP = atmos. press