Chemistry Definitions - Unit 2

Ore

Rock containing a metal compound from which the metal can be extracted

Phytomining

The use of plants to absorb metal compounds from soil as part of metal extraction

Combustion

When fuel reacts with oxygen to produce oxides and heat

Oxidation
Gain of oxygen
Loss of hydrogen
Loss of electrons

Reduction
Loss of oxygen
Gain of hydrogen
Gain of electron

Redox reaction

When both oxidation and reduction occurs at the same time

Thermal decomposition

Breaking down of a substance using heat

slag

Calcium silicate (CaSiO₃)

Rate

Measure of how fast the reaction takes place

Collision Theory

This states that in order for particles (Atoms, molecules, or ions) to react they must collide and the collision must have sufficient energy, otherwise they will simply bounce off each other without reacting

Activation energy

Minimum amount of energy needed for a reaction to occur

Catalyst

A substance which increases the rate of reaction without being used up

• Transition metals and their compounds are often used as catalysts

• Catalysts lower the activation energy

Reversible reaction

A reaction in which the products, once made, can react to reform the reactants

Exothermic reaction

releases heat (Negative direction)

Endothermic reaction

Takes in heat (Positive direction)

Irreversible reaction

reactions where the reactant convert to products and the products cannot be converted back into the eactants again

Closed system

Where no substances can get in or out

Open system

Allows entery and exit of substancess

Dynamic equilibrium

When rates of the forward and reverse reactions are equal and the amount of reactants and products remain constant

Le chatelier’s principle

States that if a change is made to the conditions of a system at equilibrium moves to oppose that change in conditions

• Concentration - If more of a chemical is added, the equilibrium position moves to remove it. If some of a chemical is removed, the equilibrium position moves to make more of it.

• Pressure - Increased, moves to the side with least molecules. Decreased , moves to to side with most molecules

• Temperature - Increased, moves in the endothermic direction. Decreased, moves in the exothermic reaction

• Catalyst has no effect

Haber Process

N₂ + 3H₂ ⇌ 2HN₃

The condictions used in industry

• temperature 450°C

• pressure 200 atm

• iron catalyst

Hydrocarbon

Molecule consisting of carbon and hydrogen atoms only

Crude Oil (Petroleum)

Mixture containing mainly alkane hydrocarbons

Petrochemicals

Chemicals made of petroleum and natural gas

Finite resource

Once used, cannot be replaced in a human life time.

Fraction

A mixture of molecule with similar boiling points

Fraction uses

Fraction	Use
Refinery gases	Bottled gases
Petrol	Vehicle fuel
Naphtha	Chemical and plastics
Kerosene	Aircraft fuel
Diesel oil	Fuel for cars and trains
Fuel oil	Ship fuel; lubricants
Bitumen	Road Tar

Homologous series

All members have the same general formula, have similar chemical properties and a gradation of physical properties. each member differs from the next by a CH2 unit

Functional group

A reactive group in a molecule that dictates its chemical properties

Unsaturated

The molecule contains one or more carbon-carbon double bond

Addition reaction

Molecule added across a C=C

Polymer

A long chain molecule made from joining small molecules together

Monomer

A small chain molecule that combines with other monomers to form a polymer

Addition Polymerisation

The process of joining monomer molecules together to form a long chain molecule

Non-biodegradable

Cannot be decomposed by natural bacteria in the environment

Cracking

The breakdown of larger saturated hydrocarbons (alkanes) into smaller more useful ones, some of which are unsaturated (alkanes)

Acidified potassium dichromate

Oxidising agent, turns some alcohols to carboxylic acid (Orange to green)

• methanol → methanoic acid

• ethanol → ethanoic acid

• propan-1-ol → propanoic acid

• Propan-2-ol can be oxidised and change colour but acid is not formed

Titrations

The accurate neutralisation of an acid with an alkali

Avogadro’s law

States that equal volumes of gases at the same temperature and pressure contain the same number of particles/molecules

Electrolysis

The decomposition(breaking down) of a substance by passing on electric current through it

Electrolyte

A liquid which conducts electricity and decomposes

Anode

Positive electrode

Cathode

Negative electrode

Bauxite

Aluminum in ore form

purifed this by using sodium hydroxide solution

Aluminium Oxide

High melting point - 2050 degrees

To reduce melting point, Aluminium Oxide is dissolved in molten cryolite, reducing melting point to ~ 1000. Cryolite also increases conductivity of the aluminium oxide

Reaction pathway

The curve from the reactants to the products

Energy change

Difference between energy of reactants and products