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OCR AS Level Chemistry > DEFINITIONS > Flashcards

Flashcards in DEFINITIONS Deck (23)
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1
Q

Activation Energy

A

the minimum energy required to start a reaction by the breaking of bonds

2
Q

Addition polymer

A

a very long molecular chain, formed by repeated addition reactions of many unsaturated alkene molecules (monomers)

3
Q

Addition Polymerisation

A

the process in which unsaturated alkene molecule (monomers) add on to a growing polymer chain one at a time to form a very long saturated molecular chain (the addition polymer)

4
Q

Addition reaction

A

a reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule

5
Q

Alicyclic hydrocarbon

A

a hydrocarbon with carbon atoms joined together in a ring structure

6
Q

Aliphatic hydrocarbon

A

a hydrocarbon with carbon atoms joined together in straight or branched chains

7
Q

Alkyl group

A

an alkane with a hydrogen atom removed, e.g. CH3, C2H5; alkyl groups are often shown as R

8
Q

Anhydrous

A

a substance containing no water molecules

9
Q

Atom economy

A

(molecular mass of the desired product/ sum of molecular masses of all products) x100

10
Q

Average bond enthalpy

A

the average enthalpy change that takes place when breaking by homolytic fission 1 mol of a given type of bond in the molecules of a gaseous species

11
Q

Bond enthalpy

A

the enthalpy change that takes place when breaking by homolytic fission 1 mole of a given bond in the molecules of a gaseous species

12
Q

Catalyst

A

A substance that increases the rate of reaction by lowering the activation energy

13
Q

Cis-trans isomerism

A

a special type of E/Z isomerism in which there is a non-hydrogen group and a hydrogen on each C of a C=C double bond: the cis isomer (Z isomer) has the H atoms on each carbon on the same side; the Trans isomer has the H atoms on opposite sides

14
Q

Compound

A

a substance formed from two or more chemically bonded elements in a fixed ratio, usually shown by a chemical formula

15
Q

Covalent bond

A

a bond formed by a shared pair of electrons

16
Q

Cracking

A

the breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes

17
Q

Dative covalent bond

A

a shared pair of electrons which has been provided by one of the bonding atoms only; also called a coordinate bond

18
Q

Dehydration

A

an elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule

19
Q

Delocalised electrons

A

electrons that are shared between more than two atoms

20
Q

Displacement reaction

A

a reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter’s ions

21
Q

Displayed formula

A

a formula showing the relative positioning of all the atoms in a molecule and the bonds between them

22
Q

Disproportionation

A

the oxidation and reduction of the same element in a redox reaction

23
Q

Dynamic equilibrium

A

the equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction