chemistry definitions Flashcards
molar mass
mass in grams of one mole of that substance
molar concentration
the amount of solute per unit volume of solution
electronegativity
a measure of the tendency of an atom to attract a bonding pair of electrons
heat of a reaction (h)
the net change of chemical potential energy of the system
exothermic reaction
reactions which transform chemical potential energy into thermal energy
endothermic reaction
reactions which transforms thermal energy into chemical potential
activation energy
the minimum energy required to start a chemical reaction
activated complex
a high energy, unstable transitions state between reactants and products
rate of reaction
as the change in amount or concentration per unit time of either a reactant or product
catalyst
a substance that increases the rate of reaction but remains unchanged at the end of the reaction
what is the collision theory
a model that explains that a reaction will only proceed when reactant particles collide effectively
what makes an effective collision
correct orientation, sufficient kinetic energy (greater or equal to activation energy)
what is a closed system
one in which mass is conserved inside the system but energy can enter or leave system freely
what is a open system
one in which both energy and matter can be exchanged between the system and its surroundings
state le chateliers principle
when an external stress (change in pressure, temperature or concentration) is applieed to a system in dynamic chemical equilbrium , the equalbrium point will change in such a way as to counteract the stress
acid
proton donor
base
proton acceptor
define ionisation
the reaction of a molecular substance with water to produce ions
what is a strong acid
an acid that ionises almost completely in an aqueous solution
weak acid
an acid that only ionises partically in an aqueous solution
dissociation
the splitting of an ionic compound in to its ions
what is a strong base
a base that dissociates almost completely in an aqueous solution
what is an amphoteric
a substance that can act as either an acid or a base
weak acid
a base that only ionises partially in an aqueous solution
salt
a substance in which the hydrogen of an acid has been replaced by a cation
hydrolysis of a salt
a reaction of an ion (from a salt) with water
neutralisation
a chemical reaction in which an acid and a base react so neither is in excess
standard solution
a solution of known concentration
redox reaction
a reaction involving the transfer of electrons
oxidation
a loss of electrons
reduction
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
electrode where reduction takes place
electrolyte
a substance that can conduct electricity due to the presence of free (mobile) ions where molten or dissolved in solution
hydrocarbon
a compound containing only carbon and hydrogen bonds
saturated compound
a compound in which all of the bonds between carbon atoms are single bonds
unsaturated compound
a compound in which there is at least on double/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 have 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
