Chemistry Definitions Flashcards
Mole
The amount of substances which contain Avogadro’s number of particles
Molar mass
The mass in grams of one mole of that substance
Molar volume
The volume occupied by 1 mole of gas at STP. 1 mole of gas occupied 22,4dm3 at 0°C (273k) and 1 atmosphere (101,3kPa)
Solution
A homogenous mixture of solute and solvent
Solute
The substance that is dissolved in the solution
Solvent
The substance in which another substance is dissolved forming a solution
Yield
A measure of the extent of a reaction, generally measured by comparing the amount of product against the amount of product possible
Intramolecular bond
A bond between atoms within molecules
Covalent bond
A sharing of at least one pair of electrons by two non metal atoms
Non-polar covalent bond
An equal sharing of electrons
Polar covalent bond
Unequal sharing of electrons leading to a dipole forming (as a result of electronegativity difference)
Electronegativity
A measure of tendency of an atom to attract a bonding pair of electrons
Ionic bond
A transfer of electrons and subsequent electrostatic attraction
Metallic bonding
Being between a positive kernel and a sea of delocalised electrons
Intermolecular force
A force between molecules, ions, or atoms of noble gases
Heat of a reaction
The net change of chemical potential energy into thermal energy
Endothermic reactions
Reactions which transform thermal energy Into chemical potential energy 
Activation energy
The energy required to form the activated complex
Activated complex
A high energy, unstable, temporary transition state between the reactants and the products
Reaction rate
The change in concentration per unit time of either a reactant or product
Catalyst
A substance that increases the rate of the reaction but remains and changed at the end of the reaction 
Affective (successful) collision
A collision in which the colliding reactant particles have the correct orientation and the sufficient energy (kinetic energy equal to or greater than the activation energy)
Closed system
A system in which mass is conserved inside the system but energy can enter or leave the system freely
Open system
A system in which both energy and matter can be exchanged between the system and its surroundings
Reversible reaction
A reaction in which products can be converted back into reactants 
Dynamic chemical equilibrium
Irreversible reaction in which the forward and reverse reactions are taking place at the same rate, and hence the concentrations of reactants and products are constant
Le Chatelier’s principle
When an external stress (change in pressure, temperature or concentration) is applied to a system and dynamic chemical equilibrium, the equilibria point will change in such a way as to counteract the stress
Equilibrium constant Kc
Temperature is the only factor which influences the valley of the equilibrium constant
Acid
A proton donor
Base
A proton acceptor 
Ionisation
The reaction of a molecular substance with water to produce ions 
Strong acid
In acid that ionises completely in an aqueous solution
Weak acid
An acid that only ionises partially in an aqueous solution
Dissociation
The splitting of an ionic compound into its ions
Strong base
A bass that dissociates completely in an aqueous solution
Weak base
A bass that only dissociates/ionises partially in an aqueous solution
Amphoteric or amphiprotic substance 
A substance that can act as either an acid or base
Salt
A substance in which the hydrogen of an acid has been replaced by a cation
Hydrolysis of a salt
Reaction of an iron (from a salt) with water
Neutralisation (or the equivalence point)
The point where an acid and base have reacted so neither is in excess 
Standard solution
A solution of known concentration
Redox reaction
A reaction involving the transfer of electrons
Oxidation
The loss of electrons
Reduction
The gain of electrons
Oxidising agent
a substance that accepts electrons
Reducing agent
A substance that donates electrons
Anode
The electrode where oxidation takes place
Cathode
The electrode where reduction takes place
Electrolyte
A substance that can conduct electricity by forming free irons when molten or dissolved in a solution
Hydrocarbon
A compound containing only carbon and hydrogen atoms
Saturated compound
A compound in which all the bonds between carbon atoms are single bonds
Unsaturated compound
A compound in which there is at least one double and/or triple bond between carbon atoms
Functional group
An atom or a group of atoms that form the centre of chemical activity in the molecule
Homologous series
A series of similar compounds which have the same functional group and the same general formula in which each member differs from the previous one by a single CH2 unit
Structural isomers
Compounds having the same molecular formula but different structural formulae
Cracking
The breaking up (cracking) of a large hydrocarbon molecules into smaller and more useful molecules (specifically a smaller hydrocarbon and one or more small alkenes)
Concentration
The amount of solute per unit volume of solution
Intramolecular bonds
Dipole dipole
London forces
Hydrogen bonds
A small atom
High electronegativity
With at least one lone pair of electrons
Strength of london forces
Influenced by size of the temporary dipoles
Which is influenced by:
No. Of electrons
Longbranched chain vs branched chain
Melting point of giant structures
Diamond
Graphite
Silicon dioxide
Melting and boiling points are high due to the large amount of energy needed to break the many strong covalent bonds
Melting or boiling points in giant ionic structures
The melting or boiling points are determined by electrostatic forces of attraction between the cations and the anions in the lattice structure
