Leaving Cert Chemistry Definitions Flashcards

Sigma bond

involves head - on(end -on)overlap of atomic orbitals

Pi bond

involves side - on overlap of p orbitals

gas that obeys the gas laws(boyles law, kinetic theory, PV=nRT) at all values of temperature and pressure/all conditions/perfectly. (allow a gas that obeys the assumptions of the kinetic theory for 6marks)

Atom

small // indivisible //identical atomic mass for a particular element

Energy level

discrete (fixed, restricted, definite) energy of electron/ energy of electron in an orbit/ orbit which electrons of equal energy can occupy.

energy Sub - level

consisting of one or more orbitals of the same energy in a main energy level.

Orbital

region (space) around the nucleus of an atom where there is a high(99%) probability of finding an electron/ where electron most likely to be found

Bond energy

average energy required to break one mole of bonds // and to separate the atoms /into separate atoms //in the gaseous state

Heat of reaction

heat change for a reaction according to a balanced equation

Heat of combustion

energy released( heat change) when one mole of a substance is burned(reacts) completely in oxygen/ is burned in excess oxygen

Heat of formation

heat energy when one mole of a compound formed from it elements

Mole

amount containing as many particles equal to the relative molecular mass expressed in grams / as many particles as 12g of carbon 12 / Avogadro number of particles

Le Chatelier's principle

if a system at equilibrium is disturbed // it tends to minimise (oppose, relieve) the disturbance (stress)

Equilibrium

the rate of the forward reaction is equal to the rate of the reverse reaction

Dynamic

reaction is always moving, has not stopped

Acid(Bronsted-Lowry)

proton donor

Base (Bronsted - Lowry)

proton acceptor

Acid (Arrehenius)

dissociates in water to produce H+ ions

Base(Arrehenius)

dissociates in water to produce OH- ions

Conjugate acid-base pair

acid and base differing by a proton(H+) / acid donates a proton to form its conjugate base; base accepting a proton to form its conjugate acid

Strong acid

good proton donor / completely dissociates in aqueous soln to produce H+ ions

Weak acid

poor proton donor /slightly dissociates in aqueous soln to produce H+ ions(accept " does not readily "; do not accept " does not completely or does not fully" )

Electronegativity

relative(measure of ) attraction /number expressing attraction// an atom of an element has for a shared pair of electrons (for a pair of electrons) in a single covalent bond

Radioactivity

spontaneous random decay of (disintegration of, decomposition of, breaking up of, change within) an unstable nucleus // to release Î±, Î², or Î³ radiation

Radioisotope

radioactive form of an element

Heisenberg's uncertainty principle

not possible to measure the exact position (location ) and momentum (energy, velocity) of an electron // in an atom simultaneously (at the same time)

Pauli's exclusion principle

no more than two electrons may occupy an orbital and they must have opposite spin.

Hund's rule of maximum multiplicity

when two or more orbitals of equal energy are available, the electrons occupy them singly before filling them in pairs.

First ionisation energy

the minimum energy required to remove the most loosely bound electron // from one mole of isolated (gaseous) atoms in their ground (lowest energy) state.

Hydrocarbon

compounds of carbon and hydrogen only

Structural isomer

compounds with the same molecular formula but different structural formulas (structures, atomic arrangements) Not chemical formula

Activation energy

minimum energy required for colliding particles to react / energy needed for colliding particles to initiate a reaction / minimum energy needed for effective collisions between particles

Ground state

in lowest energy state / in n = 1 level / in a 1s orbital

Excited state

in higher energy state / in n > 1 level / in orbital other than 1s

Atomic radius

half the internuclear distance ( half the distance between the centres) // of singly bonded atoms of the same element

Covalent bond

involving the sharing // of one or more pairs of electrons

Polymerisation

monomers (small molecules) combining (linking, joining) to form a polymer (large, big molecule)

pH

minus the log to base 10 of the hydrogen ion concentration / - log 10 [H+]

Charles law:

for a definite mass of gas, at a constant pressure,// volume varies directly with Kelvin temperature / V T

Boyles law

for a definite mass of gas at a constant temperature// pressure is inversely proportional to volume pV = k

Heterogenous catalysis

reactants and catalyst in different phases/ boundary between reactants and catalyst

Catalytic cracking

splitting (breaking) of long chain molecules (hydrocarbons) by heat and a catalyst.

Rate of reaction

change in concentration per unit time of reactants ( products) NOT accept increase or decrease for change

Hard water

water which does not easily form lather with soap

Homologous series

general formula/ differ by CH2/ same functional group/ similar chemical properties / similar method of preparation / gradation in physical properties ( give a few of these in your answer )

Relative atomic mass

average mass of atoms of an element / average of isotopes taking abundances into account //relative to ( based on) 1/12 mass of carbon - 12 atom

Volatile liquid

easily changed to gas / easily vaporised / low boiling point

48) B.O.D biochemical oxygen demand by micro - organisms

( difference between water tested immediately and Water sample left in the dark, for five days, at 20 oC )

Electrolysis

production of a chemical change when electricity passes through an electrolyte so that ions are free to move( do not accept " chemical change produced by electrical energy(current))

Standard solution

One of exact known concentration by another titration

Primary standard

Substance from which a solution of exact concentration can be made by titration // substance which is stable, available pure and is soluble in water

Catalyst

substance which alters the rate of a chemical reaction but remains unchanged itself at the end of the reaction

Free chlorine

chlorine present as hypochlorite ion ( OCl- )

Aromatic

contains a benzene ring in its structure

Ionic bond

attraction between oppositely charged ions in a crystal // bonding involves the loss and gain of electrons

Fractionation

: separating // into samples that have different boiling points

Half - life of radioactive element

time for half // of a sample to decay

Polar bond

involving unequal sharing of electrons

Diffusion

spreading out // of particles from a region of high concentration to a low concentration

Gay-Lussac's Law of combining volumes

The volumes of reacting gases and their gaseous products are in small whole number ratios measured at the same temperature and pressure

Octane number

measure of tendency to auto -ignite (knock, pre - ignite, ignite early, ignite before spark) / number representing ability to resist knocking (autoigniting) / number based on a scale where 2-2-4 trimethylpentane is assigned a rating of 100 and heptanes a value of 0 / percentage by volume of 2-2-4 trimethylpentane in a blend with heptanes that matches the behavior of a fuel

Leaving Cert Chemistry Definitions Flashcards ionicons-v5-c

Leaving Cert Chemistry Definitions Flashcards