IGCSE combined science (mod 8-)

Organic chemistry

Studies on the structure, properties, reactions of organic compounds that contain carbon in covalent bonding

Saturated hydrocarbons

Hydrocarbon molecule in which all carbon-carbon bonds are single and covalent

Alkanes

Series of hydrocarbons with the general formula CnH2n+2. Saturated because only single bonds between carbons in their structure

Unsaturated hydrocarbons

Hydrocarbon which contains at least one carbon-carbon double/triple bond

Alkenes

Series of homologous with general formula CnH2n. Unsaturated because they contain carbon-carbon double bonds

Hydrocarbon

Organic compound containing ONLY carbon and hydrogen. Ex. Alkanes, alkenes

Homologous series

Family of similar compounds and chemical properties due to having the same functional group

Functional group

Atom or group of atoms responsible for characteristic reactions of compound

General formula

Algebraic formula describing all members of a homologous series

Addition reaction

Reaction in which a simple molecule adds across the carbon-carbon double bond of an alkene

Methane formula

CH4

Ethane

C2H6

Propane

C3H8

Butane

C4H10

Pentane

C5H12

Catalytic cracking

Decomposition of long-chain alkanes into alkenes and alkanes of lower relative molecular mass. Involves passing larger alkanes over catalyst heated to 500°C

Fractional distillation

Method of distillation using a fractionating column used to separate liquids with different boiling points

Hydrogenation

Addition reaction in which hydrogen is added across the double bond in an alkane

Hydration

Addition of elements of water across a carbon-carbon double bond: H- adds to one carbon and -OH to the other

Coal

Black, solid fossil fuel former underground over very long periods of time by conditions of high pressure and temperature acting on decayed vegetation

Natural gas

Fossil fuel formed underground over very long periods of time by conditions of high pressure and temperature acting on the remains of sea creatures (90%+ methane)

Petroleum

Fossil fuel formed underground over very long periods of time by conditions of high pressure and temperature acting on remains of sea creatures

Non renewable resources

Sources of energy (often formed in the Earth over millennia) which humans are using up at a rapid rate and cannot replace

Chemical feedstock

Chemical element or compound which can be used as a raw material for an industrial process making useful chemical products

Fractions (from distillation)

Different mixtures that distil over at different temperatures during fractional distillation

Fractionating column

Vertical column used to bring about separation of liquids in fractional distillation

Polymer

Substance consisting of very large molecules made by polymerising a large number of repeating units (monomers)

Proteins

Polymers of amino acids formed by a condensation reaction which have a wide variety of biological functions

Monomer

Small molecule which can be polymerised to make a polymer

Polymerisation

Chemical reaction in which monomer molecules join together forming a long chain polymer

Amino acids

Naturally occurring organic compounds possessing both an amino (-NH2) group and an acid (-COOH) group in the molecule. The 20 naturally occurring aminos are polymerised in cells to make proteins

Endothermic reaction

A reaction in which heat is absorbed/enters the reaction. Feels cold

Exothermic reaction

A reaction in which heat exits/is released. Feels hot.

Energy level diagram/reaction pathway diagram

Diagram that shows the energy levels of the reactants and products in a chemical reaction. Shows whether reaction is exothermic or endothermic

Bond energy

Energy required to break a particular type of covalent bond

Activation energy (Ea)

Minimum energy required to start a chemical reaction; for a reaction to take place the colliding particles must possess at least this amount of energy

Reaction rate

Measure of how fast a reaction takes place

Catalyst

Substance that increases the rate of a chemical reaction but the substance itself remains unchanged at the end of the reaction

What does increasing surface area do to a reaction rate?

Increases because there are more molecules on the surface

What does increasing reactant concentration do to a reaction rate?

Increases because the no. collisions /second increases

What does increasing temperature do to a reaction rate?

Increases because collisions are more frequent and have more kinetic energy behind them

What does the presence of a catalyst do to a reaction rate?

Increases because less activation energy is needed

Collision theory

States that a chemical reaction takes place when particles of the reactants collide with sufficient energy to initiate the reaction

Absorption

Attachment of molecules to a solid surface

Positive charge

Type of electrical charge carried in the nucleus of an atom

Negative charge

Type of electric charge carried by electrons

Current

Rate at which electric charge passes a point in a circuit

Direct current (d.c)

Electric current that flows in the same direction all the time

Cell

Device that provides an electromotive force in a circuit by means of chemical reaction

Battery

Two or more electrical cells connected together in series

Alternating current

Electric current that periodically changes direction

Charge

(Pos) Carried around by the current. (Neg) carried by electrons

Conventional current

Direction positive charges would flow in a complete circuit: from positive to negative terminals of a cell. Opposite to direction electrons flow

Ammeter

Meter for measuring electric currents

Ampere/amp (A)

SI unit of electric currents

Current equation

Current (A) = charge (C) / time (s)

Current equation

I = Q/t

Voltage

_ of a source causes current to flow in a circuit

Voltmeter

Meter for measuring p.d (voltage) between two points

Parallel (in circuit)

In which components are connected in separate loops

Volt (V)

SI unit of voltage (p.d or e.m.f)

Electromotive force (e.m.f)

Voltage across terminals of a source or the electrical work done by a source in moving charge around a circuit

Potential difference (p.d)

Work done by (a unit of) charge passing through an electrical component. Also called voltage between two points

Resistance equation

Resistance = p.d / current

Resistance equation

R = V/I

Resistance

Measure of how difficult it is for an electric current to flow through a device/component in a circuit.

Ohm (Ω)

SI unit of electrical resistance