13.1 - The Nature of Gases

2 TYPES OF ENERGY

• potential - stored energy; EX food, logs, gas

• kinetic

  • energy of movement

  • kinetic theory - all matter consists of tiny particles that are in constant motion

  • high temp - fast KE

  • low temp - slow KE

APPLIES TO GASES

• small hard spheres without volume

• particles are far apart - lots of distance and space between the particles when compared to a liquid or a solid

• not attractive or repulsive forces between atoms and molecules

• no definite shape or volume

• motion of one particle is independent to all other particles

• motion of gas particles are rapid, random, and constant

• can fill any container regardless of shape or volume

• particles travel in straight line paths until they collide - these collisions are perfectly elastic (the KE is transferred from 1 particle to another with out loss of KE; total KE remains constant)

• gas pressure - results from the force exerted by a gas per unit surface area of an object

  • exert a force when they collide with each other in the container they are confined in

  • result of simultaneous collisions of billions of rapidly moving particles in a gas with an object

vacuum - empty space with no particles and no pressure

atmospheric pressure - a result from collisions of atom and molecules in the air with objects; drops as altitude increases

barometer - measures atm pressure

• Hg barometer

  • high pressure, high mercury level in tube

  • low pressure, low mercury level in tube

Pascal (Pa) - SI unit of pressure

1 standard atm - pressure required to support 760 mm of Hg in a mercury barometer at 25C

1 atm = 760 mm Hg = 101.3 kPa

low temp, low KE - high % of molecules

high temp, high KE - low % of molecules

absolute zero (0K or -273.15C) is the temp at which the motion of particles theoretically cease/no KE

the K temp of a substance is directly proportional to the average KE of the particles of the substance

13.2 - Nature of Liquids

APPLIES TO LIQUIDS

• particles are close together

• attraction between atoms and molecules

• definite volume

• takes shape of its container

• more dense than gases

• barely affected by high pressure

vaporization - liquid → gas

evaporation - escape of liquid H2O molecules to a gas state without boiling

• only the molecules with a certain minimum KE can escape from the surface of the liquid

• a cooling process

high temp, high KE, high number of molecules that transition from a liquid to a gas

vapor pressure - measure of force exerted by a gas above a liquid

• physical characteristic

condensation - gas to liquid

manometer - u shaped tool that measures vapor pressure

dynamic equilibrium - when rate of evaporation is equal to rate of condensation; constant vapor pressure

boiling point - temp at which vapor pressure of the liquid is just equal to the external pressure on the liquid

normal boiling point - bp of a liquid at 101.3 kPa

13.3 - Nature of Solids

APPLIES TO SOLIDS

• tightly packed particles

• dense, not easily compressed

• do not flow

melting - solids to liquid

freezing - liquid to solid

melting point - temp at which a solid changes to a liquid

crystal - particles arranged an an orderly, repeating, 3D pattern → forms a crystal lattice

unit cell - smallest group of particles within a crystal that retains the geometric shape of the crystal

high mp - strong intermolecular bonds

low mp - weaker intermolecular bonds

allotropes - 2 or more different molecular forms of the same element in a physical state

• carbon, phosphorus, sulfur, oxygen, boron, antimony

amorphous solid

• random arrangement

• lacks an ordered internal structure

• EX plastic, glass (transparent fusion product of inorganic substances that have cooled to a rigid state without crystallizing)

crystalline solid

• orderly

• EX salts

13.4 - changes of state

sublimation - change of a substance from a solid to a vapor without passing through the liquid phase

• occurs in solids with vapor pressures that exceed atm pressure at/near room temp

• EX solid air fresheners

phase diagram - a graph where the relationships among the different phases of a substance in a sealed container can be represented

triple point - point on a phase diagram where all 3 curves meet