Bonds versus intermolecular forces

 An intramolecular force is any force that holds together the atoms making up a molecule or compound.  Intermolecular forces are forces of attraction or repulsion which act between neighboring particles (atoms, molecules or ions). They are weak compared to the intramolecular forces, the forces which keep a molecule together.

 The London dispersion force is the weakest intermolecular force. The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles. This force is sometimes called an induced dipole-induced dipole attraction.

 Dipole - dipole forces are attractive forces between the positive end of one polar molecule and the negative end of another polar molecule.

 A hydrogen bonding is the attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atom of a different molecule. Usually the electronegative atom is oxygen, nitrogen, or fluorine, which has a partial negative charge.

This happens in covalent molecules, remember non-metal to non-metal  Dipole is when an atom is very electronegative and another atom that is significantly lower in electronegativity.  Examples are oxygen to hydrogen, Fluorine to hydrogen, not carbon to hydrogen  The very electronegative element pulls the electrons away from the less electronegative element, making a dipole moment in the molecule

 Water is primarily a liquid under standard conditions, which is not predicted from its relationship to other analogous hydrides of the oxygen family in the periodic table, which are gases such as hydrogen sulfide.oxygen familyperiodic tablehydrogen sulfide  The elements surrounding oxygen in the periodic table, nitrogen, fluorine, phosphorus, sulfur and chlorine, all combine with hydrogen to produce gases under standard conditions. The reason that water forms a liquid is that oxygen is more electronegative than all of these elements with the exception of fluorine. Oxygen attracts electrons much more strongly than hydrogen, resulting in a net positive charge on the hydrogen atoms, and a net negative charge on the oxygen atom.nitrogenfluorinephosphorussulfur chlorineelectronegative

 Because of the strong opposites of the oxygen and hydrogen, water attracts other water molecules and other dipole molecules and ionic compounds. Boiling and melting point  The stronger the bond, the more the bonds between molecules will affect the melting point or boiling point.

 Temperature is the measure of kinetic energy. The more motion the higher the temperature, the less motion the lower the temperature.  Absolute zero is the definition of no motion.

 The enthalpy change that accompanies the heating/cooling of a pure substance is determined by the equation:   ∆H = mC p ∆T   where:  ∆H = the change in enthalpy (positive for heating, negative for cooling)  m = the mass of the thing being heated (in grams)  C p = the specific heat / heat capacity – the amount of energy needed to heat the thing by 1 0 C.  ∆T = the change in temperature (in degrees Celsius).   Sample problems:   How much energy will be needed to heat 45 grams of ethanol (C p = 2.44 J/g 0 C) from 20 0 C to 40 0 C? 2196 J  If burning a single match gives off 250 J, how much hotter can it make a 50 gram block of silver (C p of silver is J/g 0 C)  C 

 The kinetic theory of gases describes a gas as a large number of small particles (atoms or molecules ), all of which are in constant, random motion. The rapidly moving particles constantly collide with each other and with the walls of the container.

 A dynamic equilibrium exists once a reversible reaction ceases to change its ratio of reactants/products, but substances move between the chemicals at an equal rate, meaning there is no net change. It is a particular example of a system in a steady state.  In other words, the ratio between products and reactants goes up then down, then up then down, never stoping  Melting-freezing, vaporization-condensation back and forth

Temperature versus pressure. Phases depend on pressure, and temperature