Unit 1

Question 1

Activated complex

Answer 1

The activated complex is a very unstable arrangement of atoms formed at the maximum of the potential energy barrier, during a chemical reaction

Question 2

Activation energy

Answer 2

The minimum kinetic energy required by colliding particles before the reaction will occur, since a high energy activated complex must be formed

Question 3

Adsorption

Answer 3

Occurs when molecules become bonded to the surface of a catalyst

Question 4

Allotrope

Answer 4

One or two or more existing forms of an element. Example: diamond, fullerene and graphite are allotropes of carbon

Question 5

Bonding electrons

Answer 5

Shared pairs of electrons from both atoms forming the covalent bond

Question 6

Chemical bonding

Answer 6

The term used to describe the mechanism by which atoms are held together

Question 7

Chemical structure

Answer 7

Describes the way in which atoms, ions or molecules are arranged

Question 8

Collision theory

Answer 8

Suggest that for a chemical reaction to occur particles must collide

Question 9

Covalent bond

Answer 9

Former when 2 atoms share electrons in their outer shell to compel the filling of that shell

Question 10

Covalent radius

Answer 10

Half the distance between the nuclei of 2 bonded atoms of an element

Question 11

Delocalised electrons

Answer 11

In metallic bonding, electrons are free from attachment to any one metal ion and are shared amongst the entire structure

Question 12

Desorption

Answer 12

Occurs when the bonds between the molecules and the surface break and the molecule leave the surface of the catalyst

Question 13

Diatomic

Answer 13

Molecules with only 2 atoms - oxygen and carbon monoxide

Question 14

Dipole

Answer 14

An atom or molecule in which a concentration of positive charges is separated from a concentration of negative charge

Question 15

Electronegativity

Answer 15

A measure of the attraction that an atom involved in a bind has for the electrons of the bond

Question 16

Enthalpy change

Answer 16

For a reaction is defined as the change in heat energy when 1 mile of reactant is converted to the product(s) at constant pressure

Question 17

Fullerenes

Answer 17

Molecules of pure carbon constructed from 5- and 6- membered rings combined into hollow structures. The most stable contains 60 carbon atoms in a shape resembling a football

Question 18

Hydrogen bonds

Answer 18

Electrostatic force of attraction between molecules containing a hydrogen atom bonded to an atom of strongly electronegative element such as fluorine, oxygen or nitrogen and a highly electronegative atom on a neighbouring molecule.

Question 19

Intermolecular forces

Answer 19

Those which attract molecules together. They are weaker than chemical bonds

Question 20

Intramolecular forces

Answer 20

Forces of attraction which exist WITHIN a molecule

Question 21

Ionisation energy

Answer 21

Energy required to remove one mole of electrons from one mole of atoms in the gaseous state

Question 22

Isoelectronic

Answer 22

Means having the same arrangement of electrons. For example, the noble gas neon, a sodium ion and a magnesium ion are Isoelectronic.

Question 23

Lattice

Answer 23

Regular 3D arrangement of particles in space. The term is applied to metal ions in a solid, and to positive and negative ions in an ionic solid

Question 24

London dispersion forces

Answer 24

The forces of attraction which result from the electrostatic attraction between temporary dipoles and induced dipoles caused by movement of electrons in atoms and molecules

Question 25

Lone pairs

Answer 25

Pairs of electrons in the outer shell of an atom which take no part in bonding

Question 26

Miscible fluids

Answer 26

Fluids which mix or dissolve in each other in all proportions

Question 27

Periodicity

Answer 27

The regular recurrence of similar properties when the elements are arranged in order of increasing atomic number

Question 28

Polar covalent bond

Answer 28

Covalent bond between atoms of different electronegativity, which results in an uneven distribution of electrons and a partial charge along the bond.

Question 29

Potential energy diagram

Answer 29

Shows the enthalpy of reactants and products, and the enthalpy change during a chemical reaction

Question 30

Properties of a substance

Answer 30

Their physical and chemical characteristics. These are often a reflection of the chemical bonding and structure of the material

Question 31

Thermochemical equation

Answer 31

States the enthalpy change for the reaction defined, with reactants and products in the states shown

Question 32

Viscosity

Answer 32

The resistance to flow that is exhibited by all liquids