Chemistry IGCSE: Term 2 23/24

molecular formula

molecular formula

number of different atoms in one molecule

emperical formula

simplest whole number ratio of the different atoms or ions in a compound

relative atomic mass

average atomic mass of the isotopes of an element compared to the 1/12th of the mass of an atom

relative molecular mass

sum of the relative atomic mass

relative formula mass

used for ionic compounds

Diatomic

two atoms found in each molecule

Monatomic

one atom found in each molecule

Polyatomic ions

Ions made up of more than one element so if they have a number for compound formula then they need brackets.

Aqueous

dissolved in water

viscosity

ability of a liquid to flowb

brittle

material that breaks instead of bending under water stress

malleable

material that can be hammered into different shapes

ductile

can be stretched into a wire

sonorous

high ringing sound when hit

solubility

ability to dissolve in a solvent

concentration

the amount of substance in a mixture. The more substance the higher the concentration.

density

mass per unit volume of a substance

electrical conductivity

ability to conduct electricity

thermal conductivity

ability to conduct heat

valency

no of electrons that can be lost/shared/gained

forming ions

forming cations/ anions

act as a catalyst

speed up chemical reactions without being used up in the reaction. (eg enzymes)

Acid

proton donor

aqueous solution of an acid

contains H+ ions

Strong acid

completely dissociates in a aqueous solution

Weak acid

partly dissociates in a aqueous solution

Base

proton acceptor

bases

oxides or hydroxides of metals

alkali

a soluble base

aqueous solution of a alkali

contains OH- ions

neutralisation

between an acid and alkali and produces water

strong acid

Completely ionise when dissolved in water

• hydrochloric acid - HC/

• Nitric acid - HNO³

• Sulphuric acid - H²SO⁴

• Phosphoric acid H³PO⁴

weak acid

Partly ionise when dissolved in water

• ethanoic acid - CH³OOH

• Propanic acid - C²H⁵OOH

• Butanoic acid - C³H⁷COOH

• ethandioic acid - HOOCCOOH

Strong alkali

Completely ionise in water

• Sodium hydroxide - NaOH

• Pottasium hydroxide - KOH

Weak Alkali

only partly ionise in water

• Aqueous Amonnia - NH⁴OH

strength of acids

measure of degree of ionisation of acid molecules

pH scale

measure of concentration of H+ ions per dm³.

Amphoteric oxide

oxides that react with acids and bases to produce a salt and a water

hydrated substance

substance chemically combined with water

anhydrous substance

substance containing no water

Water of crystallisation

water molecules present in a hydrated crystal