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Thermochemistry
Enthalphy
Chemical reactions can be classified as either:
Exothermic reaction
ΔH will always be negative
The products are at a lower energy than the reactants, they are more stable
Total energy of the reactants = total energy of the poducts + heat given out
Endothermic reaction
The product has more energy than the reactants, they are less stable
Total energy of the product = total energy of reactants + heat take in
ΔH will always be positive
Enthalpy change
Is the amount of heat energy taken in /given out in a chemical reaction
Symbol: ΔH
Its measure when the system moves from an initial state to some final state
Is the amount of energy a reactant has to gain or loss to become a product
Energy changes
Temperature
Measure of the average kinetic energy of the atoms in the system
A thermometer is used to measure the amount of energy in a certain object
Heat
Process were thermal energy is transfered
from a hotter to a cooler system
System and sorroundings
System
Refers to the chemical reaction that is taking place
Sorroundings
Refers to everything else in the universe
Intermolecular forces
Forces produced by the interaction between molecules
There are 3 types:
Dipole - dipole forces
Is the attraction and repulsion between polar molecules
Ion - dipole forces
The interaction ions and polar molecules
When they interact, the ions dissapear
Hydrogen bonds
Is a type of dipole - dipole interaction
but between molecules that have a hydrogen atom and a vey electronegative atom
like oxygen, fluorine and nitrogen
Also called hydrogen bridges
London forces
Present in all interactions
Explain interaction between non-polar molecules
Basic force between all molecules
Internal energy
Is defined as the energy associated with the random motion of molecules
It refers to the invisible microscopic energy on the atomic and molecular scale
It is separated in scale from the microscopic ordered energy associated with moving objects
For polyatomic gases
There is transitional and bond energy
More than 1 energy
For liquids and solids
These are 3 energys used
Interaction with another molecule
There is potencial energy associated with the intermolecular active forces
For an ideal monoatomic gas
Behave as sphere
Move in straight line only
Only transitional kinetic energy
1 energy
