Unit 1-Glossary

Question 1

acid

Answer 1

An aqueous solution of a substance which has a pH less than 7. There is an excess of hydrogen ions, H+ in the solution.

Question 2

alkali

Answer 2

An aqueous solution of a substance with a pH greater than 7 . There is an excess of hydroxide ions, OH- , in the solution.

Question 3

alkali metals

Question 4

Aqueous (aq)

Answer 4

Indicates that the substance has been dissolved in water.

Question 5

atom

Answer 5

The smallest particle that can be obtained by chemical means. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons

Question 6

atomic number

Answer 6

The number of protons in the nucleus of the atom.

Question 7

base

Answer 7

A compound which neutralises an acid to form a salt and water. Bases can be soluble or insoluble. Metal oxides and metal hydroxides are bases. Soluble bases form alkaline solutions

Question 8

covalent bond

Answer 8

Formed when non-metal atoms join together by sharing electrons to achieve a full outer shell of electrons (electron arrangement the same as the nearest noble gas, group 0).

Question 9

covalent compounds

Answer 9

A compound of non-metal atoms held together by covalent bonds.

Question 10

Covalent network

Answer 10

A large structure of covalently bonded atoms.

Question 11

Diatomic molecules

Answer 11

Contain two atoms. They can be elements e.g. Hydrogen, Oxygen, Nitrogen, Fluorine, Chlorine, Bromine and Iodine (H_2,O_2,N_2,F_2,Cl_2,Br_2,I₂) or compounds e.g. hydrogen chloride, HCl

Question 12

electrolysis

Answer 12

The process of breaking down of an ionic compound into its elements by the use of an electric current.

Question 13

electron

Answer 13

A very small negatively-charged particle found in the space surrounding the nucleus of an atom.

Question 14

Electron arrangement

Answer 14

The arrangement of electrons in shells (or energy levels) around the nucleus of an atom.

Question 15

element

Answer 15

A substance containing only one kind of atom. It cannot be broken down further by chemical means.

Question 16

endothermic

Answer 16

In an endothermic reaction, energy is taken in from the surroundings. There is a decrease in temperature.

Question 17

exothermic

Answer 17

A reaction in which heat energy is released. There is a rise in temperature.

Question 18

groups

Answer 18

A vertical column in the periodic table

Question 19

halogens

Answer 19

A group of very reactive non-metal elements in Group 7 of the periodic table.

Question 20

Indicator

Answer 20

A substance which changes colour at a particular pH.

Question 21

ion

Answer 21

A charged particle formed by loss or gain of electrons. When atoms lose an electron they become a positive ion (usually metals). When they gain an electron they become a negative ion (usually a non-metal).

Question 22

ionic compound

Answer 22

An ionic compound occurs when a negative ion (an atom that has gained an electron) joins with a positive ion (an atom that has lost an electron). This is usually a metal/non-metal compound.

Question 23

Isomers

Answer 23

Compounds with the same molecular formula but with a different structural formula.

Question 24

isotopes

Answer 24

Atoms of the same element that have different numbers of neutrons (different mass number).

Question 25

lattice

Answer 25

A lattice is a regular grid-like arrangement of ions in a solid ionic compound.

Question 26

mass number

Answer 26

The number of protons plus the number of neutrons in the nucleus of the atom.

Question 27

Mixture

Answer 27

Two or more substances together, but not chemically joined. They can be separated by physical means, e.g. filtering or distillation.

Question 28

Mole

Answer 28

One mole of an element is its atomic mass expressed in grams.

Question 29

molecule

Answer 29

A group of atoms held together by covalent bonds.

Question 30

neutron

Answer 30

A particle that is found in the nucleus of an atom, has a mass of 1 amu but no charge.

Question 31

noble gases

Answer 31

The elements in Group 0/8 of the periodic table. They have a full outer shell of electrons and so are unreactive.

Question 32

Nucleus

Answer 32

Found at the centre of an atom, the nucleus contains protons and neutrons.

Question 33

periods

Answer 33

The horizontal rows of the periodic table.

Question 34

Periodic table

Answer 34

The table of elements set out in order of their atomic number.

Question 35

pH

Answer 35

The number indicating the acidity or alkalinity of a solution, on a continuous scale. pH less than 7 is acidic, pH 7 is neutral and greater than 7 is alkaline.

Question 36

Precipitate

Answer 36

The insoluble solid formed in a solution during a chemical reaction.

Question 37

relative atomic mass

Answer 37

The average mass of the atoms of an element.

Question 38

solute

Answer 38

The material that dissolves in a solvent to form a solution.

Question 39

solution

Answer 39

Formed when a solute dissolves in a solvent.

Question 40

solvent

Answer 40

The liquid in which the solute dissolves in to form a solution.