Physical sciences paper 2 definitions Flashcards
Organic molecules
Molecules containing carbon atoms
Molecular formula
Chemical formula that indicates the type of atoms and the correct number of each in a molecule.
Structural formula
Shows which atoms are attached to which within the molecule. atoms are represented by their chemical symbols and lines are used to represent all the bonds that hold the atoms together.
Condensed structural formula
A notation that shows the way atoms are bonded together in a molecule but does not show all the bond lines.
Hydrocarbons
Organic compounds that consist of hydrogen and carbon only.
Homologous series
Organic compounds that can be described by the same general formula or in which one member differs from the next with a CH2 group.
Saturated compounds
Compounds in which there are no multiple bonds between C atoms in their hydrocarbon chains. example alkanes
Unsaturated compounds
Compounds with one or more multiple bonds between C atoms in their hydrocarbon chains. example alkanes
Functional group
Is a bond or an atom or a group of atoms that determines the physical and chemical properties of a group of organic compounds
Structural isomers
Organic molecules with the same molecular formula, but different structural formulae
Chain isomers
Organic molecules with the same molecular formula, but different types of chains
Positional isomers
Organic molecules with the same molecular formula, but different positions of the side chain, substituents or functional groups on the parent chain.
Functional isomers
Organic molecules with the same molecular formula, but different functional groups
Catenation
The ability of carbon to make bonds with itself.
What makes carbon special?
Carbon has 4 valence electrons and has a valency of 4
Meaning that it can form 4 covalent bonds
C-atoms can combine directly with one another, forming long chains
Carbon can form single, double and triple covalent bonds with itself.
Boiling point
The temperature at which the vapour pressure of a substance equals atmospheric pressure.
Melting point
The temperature at which the solid and liquid phases of a substance are at equilibrium.
vapour pressure
The pressure exerted by a vapour at equilibrium with its liquid in a closed system.
heat of reaction (ΔH)
The energy absorbed or released in a chemical
reaction.
Define exothermic reactions
As reactions that release energy.
Define endothermic reactions
As reactions that absorb energy.
Activation Energy
The minimum energy needed for a reaction to take place.
Activated Complex
The unstable transition state from reactants to products.
Reaction rate
The change in concentration of reactants or products per unit time.
catalyst
A substance that increases the rate of a chemical reaction without undergoing a permanent change itself.
Hydrohalogenation:
The addition of a hydrogen halide to an alkene
Halogenation:
The reaction of a halogen (Br2, Cℓ2) with a compound
Hydration:
The addition of water to a compound
Hydrogenation:
The addition of hydrogen to an alkene
Dehydrohalogenation of haloalkanes:
The elimination of hydrogen and a halogen from a haloalkane
Dehydration of alcohols:
Elimination of water from an alcohol
Cracking of alkanes:
The chemical process in which longer chain hydrocarbon molecules are broken
down to shorter more useful molecules.
Hydrolysis:
The reaction of a compound with water
Halogenation of alkanes
The reaction of a halogen (Br2, Cℓ2) with a compound
Open and closed systems:
An open system continuously interacts with its
environment, while a closed system is isolated from its surroundings.
A reversible reaction:
A reaction is reversible when products can be converted
back to reactants and vice versa.
Chemical equilibrium:
It is a dynamic equilibrium when the rate of the forward
reaction equals the rate of the reverse reaction.
Le Chatelier’s principle:
When the equilibrium in a closed system is disturbed, the
system will re-instate a new equilibrium by favouring the reaction that will oppose the
disturbance
Arrhenius theory
Acids produce hydrogen ions (H+/H3O+/hydronium ions) in aqueous solution. Bases produce hydroxide ions (OH-) in aqueous solution.
Lowry-Bronsted
An acid is a proton (H+ion) donor.
A base is a proton (H+ion) acceptor.
Strong acids
Strong acids ionise completely in water to form a high concentration of H3O+ions.
Weak acids
Weak acids ionise incompletely in water to form a low concentration of H3O+ions.
Strong Bases
Strong bases dissociate completely in water to form a high concentration of OH ions.
Weak Bases
Weak bases dissociate/ionise incompletely in water to form a low concentration of OH ions.
Concentrated Acids
Concentrated acids contain a large amount (number of moles) of acid in proportion to the volume of water.
Concentrated Bases
Concentrated acids/bases contain a large amount (number of moles) of base in proportion to the volume of water.
Dilute Acids
Dilute acids contain a small amount (number of moles) of acid in proportion to the volume of water.
Dilute Bases
Dilute bases contain a small amount (number of moles) of bases in proportion to the volume of water.
Amphiprotic or Ampholyte
A substance that can act as either acid or base
Hydrolysis
The reaction of a salt with water
Equivalence point of a titration
The point at which the acid/base has completely reacted with the base/acid.
Endpoint of a titration
The point where the indicator changes colour.
PH scale
a scale of numbers from 0 to 14 used to express the acidity or alkalinity of a solution.
Kw
the equilibrium constant for the ionisation of water
Auto-ionisation of Water
the reaction of water with itself to form H3O+ions and OH ions.
galvanic cell
as a cell in which chemical energy is converted to electrical
energy.
Define oxidation and reduction in terms of electron (e-) transfer:
Oxidation is a loss of electrons. Reduction is a gain of electrons.
Define oxidation and reduction in terms of oxidation numbers:
Oxidation: an increase in oxidation number
Reduction: a decrease in oxidation number
Define an oxidising agent and a reducing agent in terms of oxidation and reduction:
Oxidising agent: a substance that is reduced/gains electrons.
Reducing agent: a substance that is oxidised/loses electrons.
Define an anode and a cathode in terms of oxidation and reduction:
Anode: the electrode where oxidation takes place
Cathode: the electrode where reduction takes place
Define an electrolyte
as a substance of which the aqueous solution contains ions OR a
substance that dissolves in water to give a solution that conducts electricity.
Define the electrolytic cell
as a cell in which electrical energy is converted into chemical
energy
Electrolysis:
The chemical process in which electrical energy is converted to
chemical energy
