Key Terms Unit 2 Flashcards
Exothermic Reaction
Is one that releases energy to the surroundings, there is a temperature rise and ΔH is negative
Endothermic Reaction
Is on that takes in energy from the surroundings, there is a temperature drop and ΔH is positive
Enthalpy, H
Is the heat content of a system at constant pressure
Enthalpy Change
Is the heat content of a system at constant pressure
Principle of Conservation of Energy
States that energy cannot be created or destroyed only changed from one form into another
Hess’s law
States that the total enthalpy change for a reaction is independent of the route taken from the reactants to the products
Bond Enthalpy
Is the enthalpy required to break a covalent X - Y bond into X atoms and Y atoms, all in the gas phase
Average Bond Enthalpy
Is the enthalpy required to break a given type of bond in the molecules of a gaseous species
Rate of Reaction
Is the change in concentration of a reactant or product per unit time
Activation Energy
Is the minimum energy required to start a reaction by breaking bonds
Catalyst
Is a substance that increases the rate of a chemical reaction without being used up in the process. It increases the rate of reaction by providing an alternative route of lower activation energy
Homogenous Catalyst
Is in the same physical state as the reactants
Heterogenous Catalyst
Is in a different physical state from the reactants
Carbon Neutrality
Means that a chemical process such as fuel combustion does not lead to an increase in CO2 levels. Although the combustion does produce CO2 this is offset by the fact that the fuel has absorbed the same amount of CO2 in being made by photosynthesis
Functional Group
Refers to the atom/group of atoms that gives the compound its characteristic properties
Homologous Series
Is a series of compounds with the same functional group
Hydrocarbon
Is a compound of carbon and hydrogen only
Saturated Compound
Is one in which all the C to C bonds are single bonds
Unsaturated Compound
Contains C to C multiple bonds
Molecule Formula
Shows the atoms, and how many of each type there are, in a molecule of a compound
Displayed Formula
Shows all the bonds and atoms in the molecule
Shortened Formula
Shows the groups in sufficient detail that the structure is unambiguous
Skeletal Formula
Shows the carbon/hydrogen backbone of the molecule as a series of bonds with any functional group attached
The Empirical Formula
Is the formula of a compound with the atoms of the elements in their simplest integer ratio
Structural Isomers
Are compounds with the same molecular formula but with different structural formulae
Van Der Waals Forces
Are dipole-dipole or temporary dipole-temporary dipole interactions between atoms and molecules
Fossil Fuel
Is one that is derived from organisms that lived long ago
Non-Renewable Resources
Are those that cannot be reformed in a reasonable timescale
Greenhouse Gas
Is on that causes an increase in the earth’s temperature
σ bond
Is made by end to end overlap of s or p-orbitals
Complete Combustion
Is combustion that occurs with excess oxygen
Incomplete Combustion
Is combustion that occurs with insufficient oxygen
Halogenation
Is a reaction with any halogen
Initiation
Is the reaction that starts the process. A molecule is turned into two radicals
Homolytic Bond Fission
Is when a bond is broken and each of the bonded atoms receives one of the bond electrons
Radical
Is a species with an unpaired electron
Propagation
Is the reaction by which the process continues/grows. A molecule reacts with a radical to make a new molecule and a new radical
Chain Reaction
Is one that involves a series of steps and, once started, continues
Termination
Is the reaction that ends the process. Two radicals react to make a molecule.
Reaction Mechanism
Shows the stages by which a reaction proceeds
Substitution Reaction
Is one in which one atom/group is replaced by another atom/group
π bond
Is one formed by the sideways overlap of p-orbitals
E-Z Isomerism
Is isomerism that occurs in alkenes(and substituted alkenes) due to restricted rotation about the double bond
Electrophile
Is an electron-deficient species that can accept a lone pair of electrons
Heterolytic Bond Fission
Is when a bond is broken and one of the bonded atoms receives both electrons from the covalent bond. Ions are formed
Addition Reaction
Is a reaction in which reagents combine to give only one product
Carbocation
Is an ion with a positively charged carbon atom
Polymerisation
is the joining of a very large number of monomer molecules to make a long chain polymer molecule
Monomer
Is a small molecule that can be made in a polymer
Repeat Unit
Is the section of the polymer that is repeated to make the whole structure
Halogenoalkane
Is an alkane in which one or more hydrogen atoms have been replaced by a halogen
Nucleophile
Is a species with a lone pair of electrons that can be donated to an electron- deficient species
Eleminiation Reaction
Is one that involves the loss of a small molecule to produce a double bond
CFC’s
Are halogenoalkanes containing both chlorine and fluorine
Ozone Layer
Is a layer surrounding earth that contains O3 molecules
HFC’s
Halogenoalkanes containing fluorine as the only halogen
Alcohol
Is a homologous series containing - OH as the functional group
Fermentation
Is an enzyme-catalysed reaction that converts sugars into ethanol
Biofuel
Is a fuel that has been produced using a biological source
Carbon Neutral
Is a process where there is non net transfer of carbon dioxide to or from the atmosphere
Classification of Alcohols
Into primary, secondary or tertiary according to their structures
Aldehyde
Is a homologous series containing -CHO as the functional group
Carboxylic Acid
Is a homologous series containing -COOH as the functional group
Ketone
Is a homologous series containing a C=O group within a carbon chain
Characteristic Absorption
Is the wavenumber range at which a particular bond absorbs radiation
Wavenumber
Is a measure of energy absorbed, is used in IR spectra
Chemical Shift
Indicates the position for a specific environment on the NMR spectrum
Environment
Is the nature of the surrounding atoms/groups in a molecule