Key Words Flashcards
Activation Energy
Minimum energy (1)
required before a reaction can occur or go or start (1)
Atomic number
Number of protons in one atom or nucleus (1)
Catalyst
A substance that speeds up the reaction / alters the rate but is chemically unchanged at the end / not used up
Dynamic equilibrium
Rate of forward reaction = rate backward reaction (1)
concentration remains constant (1)
Electronegativity
Tendency or strength or ability or power of an atom/element/nucleus to
attract/withdraw electrons / e– density / bonding pair / shared pair 1
In a covalent bond (tied to M1 – unless silly slip in M1)
Empirical formula
Tendency or strength or ability or power of an atom/element/nucleus to
attract/withdraw electrons / e– density / bonding pair / shared pair 1
In a covalent bond (tied to M1 – unless silly slip in M1)
Enthalpy change
Heat energy change (1)
Not energy on its own
measured at constant pressure (1)
First ionisation energy
Energy required to remove one mol of electrons from one mole of gaseous atoms to form one mole of + 1 ions also in their gaseous state
Hess’s law
Enthalpy change is independent of route taken
Isotope
Atoms with the same number of protons / proton number (1)
NOT same atomic number
with different numbers of neutrons (1)
Le Chatelier’s Principle
Equilibrium opposes a change;
Mean Bond Enthalpy
Energy required) to break a given covalent bond (1)
averaged over a range of compounds (1)
Oxidation
Loss of electrons
Oxidising agent
Species that Gains electrons (or removes electrons) 1
Periodicity
Pattern in the change in the properties of a row of elements (1)
Repeated in the next row (1)
Rate of reaction
(Measured) change in concentration (of a substance) in unit time
/ given time
Reducing agent
A reducing agent loses (donates) electrons (1)
Reduction
Reduction involves gain of electrons
Real active atomic mass
Average/mean mass of (1) atom(s) (of an element) 1
1/12 mass of one atom of 12C 1
Real active molecular mas
Mean /average mass of a molecule/entity/formula 1
1/12th mass of atom of 12C
Standard Enthalpy of Combustion
Enthalpy change when 1 mol of a substance
(or compound) (QL mark) 1
is (completely) burned in oxygen (or reacted in excess oxygen) 1
at 298 K and 100 kPa (or under standard conditions) 1
Standard enthalpy change of formation
Enthalpy change) when 1 mol (1) of a compound is formed
from its constituent elements (1) in their standard states (1)
