Summer Exam Definitions Flashcards
Relative atomic mass
Average mass of an element in its ground state relative to 1/12th the mass of a carbon 12 atom
Isotope
Atoms of the same element with the same no of protons and differing numbers of neutrons
Mass number
No of protons and neutrons in an atom
Radioactivity
Spontaneous disintegration of unstable nuclei emitting one or more types of radiation
Half life
Time it takes for half the nuclei in a radioactive sample to decay
Energy level
Shell which electrons of equal energy occupy
Heisenbergs uncertainty principle
it is impossible to measure at the same time both the velocity and the position of an electron
Orbital
Region in space around the nucleus of an atom with a high probability of finding an electron
Atomic radius
Half the distance between the centre of singly bonded covalent atoms
Electronegativity
Measure of attractiveness of an electron for a shared pair of electrons in a covalent bond
First ionisation energy
Energy required to remove the most loosely bound electron from a neutral
gaseous atom in the ground state.
Ionic bonding
Bond resulting from loss or gain of electrons
Covalent bonding
Bond resulting from sharing of electrons
Intramolecular bonding
Forces within molecules, e.g. polar covalent bond
Intermolecular bonding
Forces between molecules, e.g. polar covalent compound like dipole dipole
Boyles law
At constant temperature the volume of a fixed mass of gas is inversely and proportional to its pressure
Charles law
at constant
pressure the volume of a
fixed mass of gas is
directly proportional to its temperature measured on the Kelvin scale
Mole
the amount of that substance that contains 6x1023 particles.
What do each of the following mean %w/v %v/v %w/w
S
Standard solution
Solution of known concentration
Primary standard
is a pure, stable, soluble compound from which solutions of known concentrations can be made.
Isomer
Compounds with the same molecular formula but different structural formula.
Saturated organic compound
Compounds which contain only single bonds between atoms.
Hydrocarbon
compounds consisting of hydrogen and carbon only, bonded together covalently.
They are important as fuels and feedstock for the chemical industry.
Heat of reaction
the heat change that takes place when the number of moles of reactants indicated in the balanced equation for the reaction react completely.
Heat of combustion
the heat change that takes place when 1 mole of a substance is completely burned in excess oxygen.
Heat of formation
the heat change that takes place when one mole of a compound in its standard state is formed from its elements in their standard states.
Oxygenate
Adding Oxygenates (any fuel that contains oxygen in its molecules, eg. methanol, ethanol, MTBE (methyl tertiary butyl ether) increases octane number AND gives rise to very little pollution.
Octane number
a measure of a fuels tendency to resist knocking or auto ignition.
Measured on a scale of 0-100
100 being assigned to 2,2,4 trimethylpentane and 0 being assigned to heptane.
i.e. if a fuel has a high octane number it will resist knocking and is therefore more desirable as a fuel.
Rate of reaction
This is the change of concentration of a reactant or product per unit time.
Activation energy
This is the minimum amount of energy which colliding particles must have in order to react and take place. It is the energy that must be supplied to start the chemical reaction
Catalyst
a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.
Homogenous catalyst
This occurs when both the reactants and the catalysts are in the same phase e.g. Iodine snake experiment OR ethanol and ethanoic acid
Heterogeneous catalyst
This occurs when the reactants and the catalysis are in a different phase (liquid vs. Solid)
Auto ignition
Auto ignition causes early explosion of petrol in the car which can cause the engine to lose power
