Chemistry Core 2 Definitions

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Endothermic
A reaction that takes in heat from its surroundings.
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Exothermic
A reaction that gives out heat.
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Enthalpy Change
A heat change at constant pressure.
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Standard Enthalpy of Formation
The enthalpy change when one mole of substance is formed from its constituent elements under standard conditions, with all reactants and products in their standard states.
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Standard Enthalpy of Combustion
The enthalpy change when one mole of substance is completely burned in oxygen under standard conditions, with all reactants and products in their standard states.
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Hess's Law
This states that the enthalpy change for a chemical reaction is the same, whatever route is taken from reactants to products.
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Bond Enthalpy
The enthalpy change required to break a covalent bond with all species in the gaseous state.
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Kinetics
The study of the factors that affect rates of chemical reactants - how quickly they take place.
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Collision Theory
Most collisions between molecules or other particles do not lead to reaction. They either do not have enough energy, or they are in the wrong orientation.
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Activation Energy
The minimum energy needed to start a reaction.
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Catalyst
A substance that affects the rate of chemical reactions without being chemically changed themselves.
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Heterogeneous Catalyst
A catalyst which is in a different phase to the reactants.
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Homogeneous Catalyst
A catalyst which is in the same phase as it's reactants.
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Catalytic Converter
A honeycomb made of a ceramic material and covered with platinum and rhodium metal - the catalysts.
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Dynamic Equilibrium
A situation in which the composition of a reaction mixture does not change because both forward and backward reactions are proceeding at the same rate.
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Maxwell-Boltzmann Distribution
The distribution of energies (and therefore speeds) of the molecules in a gas or liquid.
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Equilibrium Mixture
In a reversible reaction as soon as the products are formed they react together to form the reactants again, leading to a mixture of both reactants and products. Eventually a mixture is obtained in which all three components remain constant.
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Le Châtelier's Principle
If a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance.
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OILRIG
Oxidation is Loss (of electrons), Reduction is Gain (of electrons).
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Oxidation State
In an ionic compound this tells us how many electrons it has lost or gained, compared with the element in its uncombined state.
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Electronegativity
A measure of the ability of an atom to attract electrons towards itself within a covalent bond.
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Nucleophile
Reagents that attack and form bonds with positively charged carbon atoms.
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Alkene
An unsaturated hydrocarbon.
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Alkane
A saturated hydrocarbon.
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Structural Isomer
Compounds with the same molecular formula but a different structural formula.
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Positional Isomer
Two or more molecules with the same molecular formula but the functional group is in a different place. E.G CH3CH2CH2Cl and CH3CHClCH3
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Functional Group Isomer
Two or more molecules with the same molecular formula but a different functional group. E.G CH3CH2OH and CH3OCH3
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Chain Isomer
Two or more molecules with the same molecular formula but a different hydrocarbon chain.
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Other cards in this set

Card 2

Front

A reaction that gives out heat.

Back

Exothermic

Card 3

Front

A heat change at constant pressure.

Back

Preview of the back of card 3

Card 4

Front

The enthalpy change when one mole of substance is formed from its constituent elements under standard conditions, with all reactants and products in their standard states.

Back

Preview of the back of card 4

Card 5

Front

The enthalpy change when one mole of substance is completely burned in oxygen under standard conditions, with all reactants and products in their standard states.

Back

Preview of the back of card 5
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