Physics 2

Molar mass

mass in grams of one mole of that substance

molar concentration

amount of solute per unit volume of solution

electronegativity

measure of the tendency of an atom to attract a bonding pair of electrons

covalent bond

sharing atleast one pair of electrons

heat of reaction

net change of chemical potential energy of the system

exothermic reactions

reactions which transform chemical potential energy into thermal energy

endothermic reactions

reactions which transform thermal energy into chemical potential energy

activation energy

minimum energy required to start a chemical reaction

activated complex

high energy, unstable transition state between the reactants and the products

reaction rate

change in amount or concentration per unit time of either a reactant or product

catalyst

substance that increases the rate of the reaction but remains unchanged at the end of the reaction

collision theory

a model that explains a reaction will only proceed when reactant particles collide effectively

closed system

one in which mass is conserved inside the system but energy can enter or leave the system freely

open system

one in which both energy and matter can be exchanged between the system and its surroundings

reversible reaction

one in which products can be converted back into reactants

dynamic chemical equilibrium

a reversible reaction in which the forward and the 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 in dynamic chemical equilibrium, the equilibrium point will change in such a way as to counteract the stress'

acid

proton donor

base

proton acceptor

ionisation

reaction of a molecular substance with water to produce ions

strong acid

An acid that ionises almost completely in an aqueous solution

weak acid

an acid that only ionises partially in an aqueous solution

polyprotic acids

acids that can donate more than one proton

dissociation

the splitting of an ionic compound into its ions

strong base

a base that dissociates almost completely in an aqueous solution

weak base

base that only dissociates partially in an aqueous solution

amphoteric/amphiprotic

a substance that can act as either an acid or base

salt

substance in which the hydrogen of an acid has been replaced by a cation

hydrolysis

a reaction of an ion (from a salt) with water

neutralisation

a chemical reaction in which an acid and a base react so that neither is in excess

standard solution

a solution of known concentration

redox reaction

a reaction involving the transfer of electrons

oxidation

loss of electrons

reduction

gain of electrons

oxidising agent

substance that accepts electrons

reducing agent

a substance that donates electrons

anode

the electrode where oxidation takes place

electrolyte

a substance that can conduct electricity due to the presence of free (mobile) ions when molten or dissolved in solution

galvanic cell

an electrochemical cell that converts the chemical energy of spontaneous redox reactions into electrical energy

electrolytic cell

an electrochemical cell that uses electrical energy to cause a non-spontaneous redox reaction to occur. Thus, electrical energy is converted into chemical energy