IGCSE combined science (mod 5-)

Chemical symbol

A letter/group of letters representing an element in a chemical formula

Compound ion

Ion made up of multiple different atoms covalently bonded together and with an overall (often negative) charge

Molecular formula

A formula that shows the actual number of atoms of each element present in a molecule of the compound

Word equation

A summary of a chemical reaction using the chemical names of the reactants and products

Reactants (chemical reaction)

The chemical substances that react together in a chemical reaction

Products (chemical reaction)

The substance/s produced by a chemical reaction

Balanced chemical equation

A summary of a chemical reaction using chemical formulae. The total number of any atoms involved are the same on both sides of the equation

State symbol: S

Solid

State symbol: L

Liquid

State symbol: G

Gas

State symbol: AQ

Aqueous solution

Aqueous solution

Dissolved in water

Essential ionic equation for neutralisation reactions

H^+ (aq) + OH^- (aq) → H2O (l)

State symbols

Symbols used to show the physical state of the reactants and products in a chemical reaction

Ionic equation

The simplified equation for a reaction involving ionic substances. Only ions which change during the reaction are shown

Valency of Group I-IV elements

Group number

Valency of Group V-VII elements

8 - group number

Valency of Group VIII elements

0

Ionic charge for metals and hydrogen

Positive

Ionic charge for non-metals

Negative

Ionic charge for Group I-IV

Group number

Ionic charge for Group V-VII

8 - group number

Ionic charge for transition elements

Number given in brackets, eg Cu (I) = 1+

Acid

A solution that turns litmus red and has a pH of below 7

Corrosive

A substance that can dissolve or ‘eat away’ at other materials

Indicator

A substance the changes colour when added to acidic or alkaline solutions

Litmus

Most common indicator. Red in acid. Blue in alkali

colour of litmus in acid

Red

Colour of litmus in alkali

Blue

Methyl orange

Indicator which is red in acid and yellow in alkali

Colour of methyl orange in acid

Red

Colour of methyl orange in alkali

Yellow

Universal indicator

Mixture of indicator dyes that has different colours in solutions of different pH

Colour of universal indicator in acids

Warm (red/orange/yellow)

Colour of universal indicator in alkali

Cool (blue/purple)

Colour of universal indicator in neutral

Green

Base

Substance that neutralises an acid, producing only a salt and water

Alkali

A soluble base that turns litmus blue and has a pH above 7

Soluble

A solute that dissolves in a particular solvent

Neutralisation general equation

Acid + base → salt + water

pH scale

Scale running from 0-14, used for expressing the acidity/alkalinity of a solution. A neutral solution has a pH of 7

Salt

Ionic compound made by the neutralisation of an acid with a base/alkali. Eg, copper (II) sulfate and potassium nitrate

Neutralisation

A chemical reaction between an acid and a base to produce a salt and water only

Insoluble

Substance that does not dissolve in a particular solvent

Salt

A compound made when a metal takes the place of hydrogen in an acid

Acid + metal →

→ salt + hydrogen

Acid + base →

→ salt + water

Acid + metal carbonate →

→ salt + water + carbon dioxide

Acidic oxide

Oxide of a non-metal. Reacts with bases. Dissolves in water to form an acidic solution

Basic oxide

Oxide of a metal. Reacts with an acid to neutralise it.

Sodium salts solubility

All are soluble

Potassium salts solubility

All are soluble

Ammonium salts solubility

All are soluble

Nitrate (salt) solubility

All are soluble

Chloride (salt) solubility

Most are soluble apart from silver chloride and lead (II) chloride

Sulfate (salt) solubility

Most are soluble, apart from barium sulfate, lead (II) sulfate and calcium sulfate

Carbonate (salt) solubility

Most are insoluble. Only sodium, potassium and ammonium carbonates are soluble

Precipitation

The sudden formation of a solid when either two solutions are mixed or a gas is bubbled into a solution

Titration reaction

In which an indicator is used to show when a reaction has taken place. One drops the acid solution into the alkali until a colour change. It is then repeated without the indicator, then the salt is evaporated as usual. Usually when both reactants are clear.

Malleability

Ability of a substance to be bent or beaten into shape

Thermal conductivity

The ability to conduct heat

Alloys

Mixtures of elements designed to have the properties useful for a particular purpose

Brass

Alloy of copper and zinc (it is hard)

Ductile

Word used to describe the property that metals cab be drawn out and stretched into wires

Reactive metals with water/steam reaction

Metal + water → metal hydroxide + hydrogen

Moderately reactive metal with dilute acid reaction

Metal + hydrochloric acid → metal chloride + hydrogen

Group I metals physical properties

Low melting point/low density/highly reactive with air and water/density increases as you go down/metals get softer as you go down

Alkali metals

Elements in group I of the periodic table which form an alkaline solution when reacted with water. Generally the most reactive group of metals

Transition metals physical properties

Not very reactive/hard and strong/high density/high melting and boiling points/often act as catalysts/many compounds are colourful

A² - B² = (A+B)(A-B)

The difference between two squares

A² = B² + C²

Pythagoras’s theorem

Stainless steel

Alloy of iron that resists corrosion, contains a significant proportion of chromium which results in the alloy being resistant to rusting

Composition of brass

70% copper / 30% zinc

Bronze composition

90% copper/ 10% tin

Mild steel composition

99.7% iron /0.3% carbon

Stainless steel composition

74% iron / 18% chromium / 8% nickel / <1% carbon

Solder composition

50% tin / 50% lead

Reactivity series (definition)

An order of reactivity, giving the most reactive metal first based on a results from a range of experiments involving metals reacting with oxygen, water, dilute hydrochloride acid and metal salt solutions

Reactivity series

Very reactive. K, Na, Ca, Mg, (Al), C, Zn, Fe, H, Cu, Ag, Au .Not reactive

Rusting

The corrosion of iron/steel to form hydrated iron (III) oxide

Ore

A naturally occurring mineral from which a metal can be extracted

Reduction reaction

The removal of oxygen from a metal/metal more

Hematite

The major ore of iron. Iron (III) oxide

Blast furnace

Furnace for extracting metals (mostly iron) by reduction with carbon that uses hot air blasted in at the base of the furnace to raise the temperature

Limestone

A form of calcium carbonate

Mineral

A naturally occurring rocks containing a particular compound