Chemistry Definitions

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  • Created by: samstarrz
  • Created on: 11-04-14 13:58
Isotopes
Versions of an element with the same number of protons but different numbers of neutrons
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Nuclear fusion
When two small nuclei combine to make a larger nucleus (high temperature)
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Half life
The time taken for half the radioactive nuclei in a sample to decay
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Atomic absorption spectra
Black lines on a coloured background
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Atomic emission spectra
Coloured lines on a black background
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Entropy
A measure of the degree of disorder
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Enthalpy change
The heat energy transferred in a reaction (per mole) under standard conditions
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Enthalpy change of reaction:
Energy absorbed by breaking bonds - energy released in making bonds
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Endothermic reactions
Absorb energy so delta H is positive
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Exothermic reactions
Release energy so delta H is negative
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Hess' law
The total enthaply change is independent of the route taken
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Catalyst
Speeds up a chemical reaction (by offering an alternative route with a lower activation enthalpy) but can be recovered chemically unchanged at the end of the reaction
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Heterogeneous catalyst
A catalyst in the same state as the reactants
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Homogeneous catalyst
A catalyst in a different state to the reactants
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Arene/aromatic compounds
Compounds with a benzene ring structure
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Aliphatic compounds
All other organic compounds (apart from arenes)
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Structural isomers
Have the same molecular formula but different structures
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Isomerisation
Creates branched-chain isomers
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Reformation
Converts alkanes into cyclic compounds e.g. cycloalkanes and arenes
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Octane number
A measure of a fuel's tendency to self-ignite (high number = less likely)
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Reduction
gain of electrons
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Oxidation
loss of electrons
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Electronegativity
the ability to attract the bonding electrons in a covalent bond
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Polar molecule
Has an overall dipole
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Non-polar molecule
Where the dipoles cancel each other out
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Ionisation enthalpy
The energy needed to remove 1 electron from an atom in 1 mole of gaseous atoms
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Collision theory
Particles must collide with enough energy to react and in the right direction
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Dynamic equilibrium
When the rate of production of reactants and products are the same in a closed system
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Le Chatilier's principle
If reaction conditions are changed, the position of equilibrium will move to try and counteract the change
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Heterolytic fission
Where bond breaking results in two different ions being formed (a cation and an anion)
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Homolytic fission
Where bond breaking results in two radicals are formedq
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Radicals
particles with an unpaired electron
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Alcohols
have an OH group
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Aldehydes
have C=O group at the end of the carbon chain
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Ketones
have C=O group anywhere except the end of the chain
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Carboxylic acids
have carboxyl group -COOH
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Ethers
contain C-O-C
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Addition polymerisation
Where monomers join together to form long chains (polymers)
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Copolymers
Made from more than one type of monomer
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Thermoplastic
Polymers that can be heated and remoulded
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Thermoset
Polymers with covalent cross-links meaning that they can't be heated and remoulded
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Stereoisomers
Have the same structural formula but a different arrangement in space
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E-isomers
where the same groups are on different sides of the double bond
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Z-isomers
where the same groups are on the same side of the double bond
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Card 2

Front

When two small nuclei combine to make a larger nucleus (high temperature)

Back

Nuclear fusion

Card 3

Front

The time taken for half the radioactive nuclei in a sample to decay

Back

Preview of the back of card 3

Card 4

Front

Black lines on a coloured background

Back

Preview of the back of card 4

Card 5

Front

Coloured lines on a black background

Back

Preview of the back of card 5
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