genchem2

Intermolecular forces

exist between  molecules and influence physical properties

 motion of molecules

In the gaseous phase, molecules are in  random and constant motion. Each gas molecule moves independently of the others

London dispersion force

 is the weakest of the intermolecular forces. This is the force  between two nonpolar molecules. It tends to be stronger the larger the atom or the molecule

Dipole-dipole

interaction occurs whenever two polar molecules get near each other. The  positively charged portion of one molecule is attracted to the negatively charged portion of  another molecule. Example interaction between two sulfur dioxide (SO2) molecules, hydrogen  bonding is considered a specific example of a dipole-dipole interaction always involving  hydrogen. 

Hydrogen bonding

 refers to the electrostatic interaction between a hydrogen and a lone  electronegative pair of atom. Usually, the electronegative atom is fluorine, nitrogen or oxygen,  which has a partial negative charge. The hydrogen atom then has the partial positive charge. 

Ion-dipole

interaction occurs when an ion encounters a polar molecule. In this case, the charge  of the ion determines which part of the molecule attracts and which repels. 

Pure water

 basically colorless, odorless, and tasteless.

Water

is an  excellent solvent for ionic compounds and for substances that can form bonds with hydrogen. 

Water

is unique because it is the only substance found in three physical states - solid, liquid,  and gas

Cohesion

refers to the attraction of molecules for other molecules of the same kind

adhesion

is the attraction of molecules of one kind for molecules of a different kind.  Cohesion is responsible for surface tension of water, the tendency of a liquid’s surface to  resist rupturing when placed under great stress or tension.

liquid water has a density of 0.9998 g/mL

what is the density of liquid water at ^oC?

liquid water has a density of 1 g/mL

what is the density of liquid water at 4 ^oC?

solid ice has a density of 0.9167  g/mL

what is the density ofsolid ice at ^oC?

Thermochemistry

the study of heat change in chemical reactions

Heat

he transfer of thermal energy between two bodies that are at different temperatures c.

Surroundings

: the rest of the universe outside the system 

Open system

a type of system that can exchange mass and energy 

 Closed system

 a type of system that allows the transfer of energy (heat) but not mass. g.

Exothermic process

any process that gives off heat or transfers thermal energy to the  surroundings

Endothermic process

any reaction in which heat has to be supplied to the system by the  surroundings 

Thermodynamics:

The scientific study of the interconversion of heat and other kinds of energy k. State of a system: defined by the values of all relevant macroscopic properties (i.e.  composition, energy, temperature, pressure, and volume) 

State functions

 properties that are determined by the state of a system, regardless of how the  condition was achieved 

 First Law of Thermodynamics

 states that energy can be converted from one form to another;  but cannot be created nor destroyed 

rate law

expresses the relationship of the rate of a reaction to the  rate constant and the concentration of the reactants raised to the same powers

Isolated system