States of Matter Chapter 10

Chapter 10 Study List Solids-characteristics Kinetic energy Melting/freezing Crystalline solid Amorphous solid Sublimation Deposition Phase diagram-interpret Phase changes Energy loss/gain with changes Read Ch 10 –all Practice 1-14, 17-19, 20-24, 29-30, 35,37, 39, 41, 42, 46-55 http://www.chemtutor.com/sta.htm#gas Kinetic energy Kinetic theory Gas pressure Atmospheric pressure High, low pressure Converting from one pressure unit to another Kelvin Relationship bet. Kelvin & KE Absolute zero Liquids-characteristics Boiling Vaporization Vapor pressure

Kinetic Energy Kinetic-motion Kinetic energy energy of motion Kinetic energy helps determine phase of substance

Kinetic Theory basic assumptions gas composed of particles hard spheres w/ large empty spaces between No attractive or repulsive forces between atoms, molc. particles in a gas move rapidly in constant random motion Fill container Move rapidly Change direction when collide

all collisions are elastic More KT all collisions are elastic energy transferred from 1 particle to another total KE const.

force exerted per area by a gas Gas Pressure force exerted per area by a gas P=Force/Area Based on collisions more collisions greater pressure Measured in pascals (Pa)

Atmospheric pressure Measures collisions of air molc. Decreases with increase in altitude Measured by barometer Units 101.3 kPa = 760 mm Hg = 1 atmosphere Standard pressure (of STP)

Weather and pressure high pressure - sinking air – clear, often cool low pressure -rising air, clouds, precipitation

Solve this: On a clear day in January, the air pressure is 1.01 atm. What is the air pressure in kPa, mm Hg? 1.01 atm x 101.3 kPa =102.3 kPa 1 atm 1.01 atm x 760 mm Hg = 767.6 mm Hg

Kelvin temperature When a substance is heated: Temperature Some energy is stored as potential energy with no change in temp Remaining energy increases motion of particles-KE Temperature measures average KE of particles (not all part. have same KE) Higher temp=higher avg. KE

Kelvin Temperature scale direct measure of avg. KE @ 200K particles have 2x avg. KE of those particles at 100K Absolute zero –theoretically where all molecular motion ceases In lab 0.0000000001 from 0 K (1 x 10-10) Water (freeze 273 K, boil 373 K)

Solids definite volume, shape ; do not flow forces held together stronger than liquids so more energy is needed to break apart

Solids Crystalline repeating 3-d arrangement of atoms specific melting point Regular shape Same chem formula may give different crystal shapes- allotrope Carbon - diamond, graphite

X-stal

solids Amorphous irregular arrangement of atoms melts over a range of temps. Ex. glass, plastics, rubber particles vibrate with definite spatial limitations so some kinetic energy

Liquids Fluid that flows-particles slide by each other Move more slowly than gases particles held together by weak attractive forces disruptive motion of particles Interplay between attraction and disruption of particles liquids more dense than gases-why?

Phase change Vaporization Evaporation Liquid to gas (vapor) Evaporation Vaporization that is not at boiling point Liquid evaporates more quickly when heated-why? Increasing avg KE, more particles can overcome attractive force that keeps them together in liquid Evaporation is a cooling process-why? Those with highest KE leave the liquid, slower molc remain, avg KE decreases so temp decreases

Liquids - Vapor Pressure Closed container/system Evaporated particles create pressure on container Reach equilibrium Rate of evaporation=rate of condensation Vapor pressure influences rate of evaporation Humid day vs dry day-when is evaporation faster? Why?

Boiling point Temperature at which vapor pressure is equal to external pressure Increase KE allows particles to overcome attractive force and escape Lower pressure, lower boiling point

Inc. in air pressure, inc. b.p. pressure cooker 2 atm 120oC Water Sea Level: 100o C Denver = 1 mi. ~ 95o C Mt. Everest (28,028’) = 70o C Inc. in air pressure, inc. b.p. pressure cooker 2 atm 120oC

Melting and freezing points Melting point Temperature at which solid changes to liquid Heat is added, speeds molc., breaks attraction between molc. Freezing point Heat is lost by substance Molc slow to where attraction is greater than motion Freezing and melting points are same temperature Water-both 0 o C or 273 K

Phase changes Phase diagram Shows the relationship between pressure, temperature and phase of substance Triple point-temp and pressure conditions where substance can exist in all three phases

Phase changes Substances change phase as energy is added to or lost from substance Particles slow down (energy loss) or speed up (energy gain) Energy gain-melting, vaporization/boiling, sublimation Energy loss-freezing, condensation, deposition

And those words are.. Sublimation-solid to gas without passing through liquid phase High vapor pressure Examples- CO2, ice in freezer, iodine Deposition-gas to solid without passing through liquid phase Examples-Snow, frost

Phase changes with diagram