Definitions - Chemistry

Question 1

Pure substance

Answer 1

Consists of one type of substance only and are made up either of elements or compounds. Have a constant composition

Question 2

Element

Answer 2

A substance which can not be broken down further into simpler substances. Consists of only one type of atom

Question 3

Compounds

Answer 3

Formed when two or more elements combine chemically with each other in a fixed ratio

Question 4

Mixture

Answer 4

Combination of two or more substances in which the substances retain their own properties. Can be present in any ratio

Question 5

Homogenous mixture

Answer 5

A mixture in which the composition of the mixture is the same throughout and consists of two or more substance in the same phase .

Question 6

Heterogenous mixture

Answer 6

A mixture in which the composition of the mixture is not uniform

Question 7

Temperature

Answer 7

An object is proportional to the average kinetic energy of its particles

Question 8

Melting point

Answer 8

The temperature at which a solid changes to a liquid

Question 9

Freezing point

Answer 9

The temperature at which a liquid changes to a solid

Question 10

Boiling point

Answer 10

The temperature at which a solid changes into a gas, or a gas changing into a liquid.

Question 11

Evaporation

Answer 11

Takes place at any temperature, at the surface only

Question 12

Sublimation

Answer 12

When a substance changes straight from a solid to a gas

Question 13

Atomic number

Answer 13

The number of protons in an atom.

Question 14

Mass number

Answer 14

The number of protons plus neutrons in an atom

Question 15

Isotopes

Answer 15

Atoms of the same element which have different mass numbers. They have the same number of protons in the nucleus, but different number of neutrons

Question 16

Ion

Answer 16

A charged atom

Question 17

Cation

Answer 17

A positively charged atom because it has lost an electron

Question 18

Anion

Answer 18

A negatively charged atom because it has gained an electron

Question 19

Orbitals

Answer 19

Region in space where probability of finding an electron is greatest.

Question 20

Valance electrons

Answer 20

Electrons on the outer most energy level

Question 21

Core electron

Answer 21

Electrons on the inner, full energy levels.

Question 22

Atomic radius

Answer 22

The radius of the atom, from the nucleus to the outermost electrons

Question 23

Ionisation energy

Answer 23

Energy required to remove one electron from a single atom in the gaseous phase

Question 24

Electron affinity

Answer 24

Amount of energy liberated when an electron is added to a single atom in the gaseous phase

Question 25

Electronegativity

Answer 25

Indication of the attractive force which an atom exerts on a shared electron

Question 26

Ionic bond

Answer 26

Regarded as a transfer of electrons. Occurs between a metal and a non metal

Question 27

Covalent bond

Answer 27

Regarded as the sharing of electrons between 2 atoms. Occurs between two non metals

Question 28

Molecule

Answer 28

A group of covalently bonded atoms

Question 29

Double bond

Answer 29

There are two bonding pairs between the atoms

Question 30

Triple bond

Answer 30

Each atom shares three electrons with another atom.