An instrument that measures atmospheric pressure.

A base is a proton acceptor. It is also a substance that can neutralise an acid.

The biosphere is the lithosphere, hydrosphere and atmosphere, including all the living organisms on earth.

Bohr proposed a model of the atom consisting of a small positively charged nucleus in the middle, which is surrounded by negatively charged particles (electrons) moving in specific circular orbits around the nucleus.

The temperature at which a substance changes phases from liquid to gas at standard atmospheric pressure. The physical point of boiling of a liquid is when the vapour pressure = the atmospheric pressure and will be different at different atmospheric pressures.

The angle between two atoms that are bonded to a central atom.

The amount of energy needed to break a bond between two atoms in a molecule.

The different intramolecular forces that keep atoms together in a molecule

The distance between the nuclei of two bound atoms.

The volume (V) of an enclosed mass of gas is inversely proportional to the presssure (p) thereof, at a constant temperature.

A property of certain materials that they are hard, but break easily.

The spontaneous and random movement of microscopic particles in liquids and gases due the their collisions against each other in the medium.

An acid is a proton donor - It will release protons in the presence of a base. A base is a proton acceptor - It will accept protons in the presence of an acid.

Compounds consisting of only carbon and hydrogen.

A functional group in organic chemistry composed of a carbon atom double-bonded to an oxygen atom.

A functional group in organic chemistry consisting of both a carbonyl and a hydroxyl group (-COOH) attached to the same carbon atom.

An organic compound that contains a carboxylgroup (-COOH).

Flat surface with an x-axis and a y-axis as perpendicular reference lines.

A catalyst changes the rate of a reaction without becoming part of the reaction.

The electrode where reduction takes place - electrons enter the electrode.

An atom that has lost one or more electrons to form a positive ion.

A concise way to represent the reactions in an elektrochemical cell. The anode and cathode are separated by two vertical lines which represents the salt bridge. The oxidation reaction (at the anode) is written left of the lines and the reduction reaction (at the cathode) is written right of the lines.

The cell potential (emf) is a measurement of the ability of a cell to provide energy. The emf of a battery is the total energy per coulomb that is transferred to the charges in the external circuit PLUS the energy per coloumb transferred to the charges while they are moving through the battery. (Emf = voltages across the external circuit plus the voltage across the internal resistance of the cell)

Molecules that have the same molecular formulae, but different chain structures.

The volume (V) of a given mass of gas is directly proportional to the absolute temperature (T) of the gas at constant pressure.

The force that keep the atoms together in a molecule.

A permanent change in the chemical nature and composition of a substance to form a new substance.

The point in a chemical reaction where the forward reaction takes place at the same rate as the reverse reaction. Although the raction is still continuing the concentrations of the reagents and products do not change any more.

The properties of a substance that makes it unique and which can only change if the substance undergoes a chemical change.

In chemical reactions substances react with each other to form new substances. The chemical composition and properties of the new products are different to that of the reagents.

A system where the total mass of the system remains constant during a chemical reaction, but energy transfer between the system and the surroundings can still take place.

A circuit is closed when an electric current can flow uninterrupted through the circuit.

Sources of light which emit continous light waves of the same wavelength and frequency and where the light waves are in phase (laser).

A model that explains rate of reaction as the result of particles that collide with a certain minimum energy.

An exothermic reaction between a substance and oxygen.

An exothermic reaction between an alkane and oxygen. Normally this is a non-spontaneous reaction that requires activation energy to start the reaction.

A compass indicates the direction of a magnetic field because the compass needle always points North.

A pure substance that constist of 2 or more different atoms.

Contains a large amount of acid substance per unit volume of the solution.

Contains a large amount of base substance per unit volume of the solution.

A solution containing a relative large amount of solute per unit volume of solvent.

The number of moles of solute per unit volume of the solution.

A physical reaction when a substance changes from gas phase to liquid phase.

A chemical reaction where monomers with different functional groups react with each other to form a long chain with the emission of smaller molecules, usually water.

Shows the most important/functional groups in an organic molecule in detail and the rest in condensed form.

The degree to which a specific material conducts electricity or heat.

A conjugated acid-base pair is where a reagent and a product only differs in the number of H+ they have.

The net charge (Qnet) of an isolated system remains constant during any physical process. In the example - two charges make contact and then separate.

The total energy in a system cannot be created or destroyed, only be transformed from one form into another form.

The total mass of the reagents and the products in a closed system will remain the same, irrespective of the reactions that take place in the system.

The total mechanical energy (EM = sum of gravitational potential energy and kinetic energy) in an isolated system remains constant.

The total linear momentum of an isolated system remains constant (is conserved).

A conservative force is one where the work done to move an object from one point to another point is independent of the route taken. Thus the net work done by a conservative force to move an object around a closed path (starting and ending at the same point) is zero.

When two waves cross each other in such a way that the crest of the one wave meets the crest of the other wave, the result is an increase in the amplitude (superposition).

The force that an object exerts on another object when they are in contact with each other.

The industrial process for producing sulfuric acid.

The complete electromagnetic spectrum that contains all the wavelengths (white light).

Opposite to electron current. The direction that positive charges will flow in a conductor.

The electrons that are found in the inner completely filled energy levels.

The unit of electric charge. 1 Coulomb is the charge that moves through a conductor if a current of 1 ampere flows for 1 second.

The force between two charges is directly proportional to the product of the charges and inversely proportional to the distance between them squared.

Atomic structure that only shows the covalent bonds between atoms, with the bonding electrons depicted as lines.

A bond where at least one pair of electrons are shared between two atoms.

Bond where the bonding electrons are shared equally between the atoms.

Bond where the bonding electrons are not equally shared between the atoms and leads to the forming of a dipole.

Covalent network structures consist of giant repeating lattices of covalently bonded atoms. Found in diamond, graphite, SiO₂ and some boron compounds.

A chemical process where long carbon chains are broken down into smaller molecules.

That angle of incidence that produces an angle of refraction of 90° when light passes from an optical more dense medium to an optically less dense medium.

Three dimensional regular repeating pattern of atoms, molecules or ions in a crystaline substance.

Water that forms part of the crystal structure of certain salts.

The rate at which charge flows.

The minimum reverse potential that has to be applied across a photo-cell to just stop the flow of the current.

A bond that forms when an atom with an incomplete complement of electrons in its valence shell can share a lone pair of electrons donated by another atom to form a molecule .

Generator that produces a direct current (DC) because it has only one split ring.

Breaking a vector down into two perpendicular components.

A reaction in which a complex compound is broken down into simpler substances. One method is through electrolysis.

The elimination of a hydroxyl (OH) group and a hydrogen atom (H) from adjacent carbon atoms to form an alkene and water. Heat is needed for the reaction to take place.

The elimination of hydrogen and a halogen from a haloalkane to form an alkene and a hydrogenhalide.

Valence electrons that are not bound to a specific atom, but are shared between the atoms (metalic bonds).

The ratio of the mass of a substance to its voume. Also the number of atoms/molecules per unit volume

The variable that changes as the independent variable changes. On a graph it always comes on the y-axis

When two waves cross each other in such a way that the crest of the one wave meets the trough of the other wave, the result is a decrease in the amplitude.

The ability of a wave to spread out in wave fronts as it passes through a small opening or around a sharp edge.

A physical reaction where a substance spontaneously moves from an area of higher concentration to an area where the substance is in lower concentration.

Contains a small amount of acid substance per unit volume of the solution.

Contains a small amount of base substance per unit volume of the solution.

A solution that contains a relative small amount of solute per unit volume of solvent.

An electronic component with the property that an electric current can only flow in one direction through it.

An acid that can donate two protons per acid molecule.

(DC) - Electric current where the flow of charge is in one direction only.

When a change in one variable leads to an equal change in the other variable.

A vector quantity depicting the net change in position from the initial to the final position.

A chemical reaction where an ion of a more reactive element replaces the ion of a less reactive element to form a new substance.

A reaction between a substance and water where bonds are broken to form hydrated ions.

The process in which solid ionic crystals break up into ions in water.

The actual path that an object follows to move from one point to another, taken along the route of movement.

The phenomonen that the pitch or frequency of sound waves (or light waves ) as detected by a listerner, changes if the source of the waves and the observer move relative to one another. The source and the listener will then have different velocities relative to the medium of sound propagation.

Covalent bond where two atoms share 4 electrons (two electron pairs).

The property of metals that can be bent or pulled into different shapes.

The reflection of sound waves from a surface. The time lapse between the sound and the echo is determined by the distance the sound wave has to travel forward and backward.

Effective collision between molecules will lead to an activated complex forming.

A collision in which both momentum and kinetic energy are conserved.

The electrical field at a point is the electrostatic force experienced per unit positive charge placed at this point.

Imaginary lines that indicate the direction in which a positive test charge will move if it is placed in the field.

The force (F) that a positive unit charge will experience at a point in the field.

An electric motor converts electrical energy into mechanical energy.

Material that can conduct electricity.

A material that does not conduct an electric current.

The energy that an electricaly charged object has because of its position in an electric field.

There are two kinds of electrochemical cells - an electrolytic cell converts electrical energy into chemical energy, while a galvanic cell obtains electricity from the cell by converting chemical energy into electrical energy.

A redox reaction in which chemical energy is converted into electrical energy.

An electrical conductor that carries an electric current into and from an electrolyte.

The chemical process in which electrical energy is converted into chemical energy. Chemical decomposition occurs at the electrodes as the electric current passes through the electrolyte.

A solution / liquid / dissolved substance that conducts electricity through the movement of ions.

In an electrolytic cell the composition of chemicals is changed when electrical energy from an external source is transferred to the chemicals in a process called electrolysis. The reactions at the electrodes are sustained by a supply of electrical energy being converted into chemical energy.

A temporary magnet that is formed when an electric current runs through a wire that is wound around a magnetic material like iron. When the current stops the magnet dissapears.

The induction of an emf and current in a closed circuit when the magnetic flux surrounding the conductor change.

The interaction between electric fields and magnetic fields in that a change in the one induces a change in the other.

Sub atomic particle with a negative charge found in the space around the nucleus.

The energy that is released when an electron is added to a neutral atom in its gas phase to form an ion.

The flow direction in which the negatively charged electrons will flow in a circuit, which is from negative to positive.

A schematic representation of the arrangement of electrons in the orbitals of an atom.

A measurement indicating how strong an atom in a molecule will attract a shared electron pair towards itself. On the Pauling scale F has the highest value of 4.0, with Cs the lowest at 0.7.

Coating a metal object with another metal by electrolytic deposition . The (positive) coating ions in the electrolyte are attracted by the negatively charged target.

The attraction or repulsion forces that charges in an electric field exert on each other.

The study of charges that are not moving.

A pure substance composed only of one type of atom and which cannot be decomposed into simpler substances by any physical or chemical process.

When two atoms or a group of atoms are removed from adjacent carbon groups in a saturated hydrocarbon and two products are formed.

The total energy supplied per coulomb of charge by the cell.

The simplest ratio in which atoms of different elements bind to form a molecule.

The end point of a titration is reached when the indicator changes colour.

A chemical reaction that requires energy. The products have more potential energy than the reagents had. ∆H is positive.

The net change in chemical potential energy of the system.

An indication of the degree of disorder in a system.

A single force that has the same effect as the resultant of two or more forces, but it is exerted in the opposite direction.

Kw (ionic product or ionisation constant of water) is the equilibrium constant for the ionisation of water. Also known as the dissociation constant.

The ratio of the equilibrium concentrations of the products raised to the power of their stoichiometric coefficents and the equilibrium concentrations of the reactants raised to the power of their stoichiometric coefficents.

Also called stoichiometric point of a chemical reaction. The point in a titration where chemically equivalent quantities (equal molar amounts) of an acid and a base have been mixed.

An organic compound with -C00- as a functional group.

The process by which ecosystems, like rivers or dams, become enriched with inorganic plant nutrients (nitrogen and phosphorus), resulting in excessive plant growth. Can be accelerated by effluent and leaching of fertilizers from the soil.

Physical change from the liquid phase to the gas phase.

A chemical reaction during which energy is released. The products have less potential energy than the reagents had. ∆H is negative.

The forces that are exerted from outside the system on objects within the system.

An emf is induced in a conductor when the magnetic field around the conductor changes. The magnitude of this induced emf (ε) in an electric circuit is directly proportional to the rate of change of the magnetic flux (Ø) through the circuit.

A substance that can be magnetised by a magnetic field and will remain a magnet after the magnetic field has been removed.

The liquid that is recovered during filtration.

A mechanical or physical process to separate a solid precipitation from a liquid by interposing a medium through which only the fluid can pass

The interaction between two objects in the form of either a pulling or a pushing force.

A sketch of the object of interest with all the forces acting on it drawn as arrows.

The extraction of individual components from a mixture by utilising their different boiling points to separate them.

The motion of an object when gravitational force is the only force working in on it.

The object of interest is drawn as a dot and all the forces acting on it are drawn as arrows pointing away from the dot.

The specific temperature at which a substance changes phases from liquid to solid (the solid phase and the liquid phase are in equlibrium).

The number of waves that move past a particular point in one second. Inverse of period (f = 1/T ).

The force acting parallel with the contact surface that opposes the motion of an object.

An atom, group of atoms, or a bond that determines the physical and chemical properties of a group of organic compounds.

Molecules with the same molecular formula, but with different functional groups.

In a galvanic cell (voltaic cell) electrical energy is obtained from the cell when chemical energy is converted into electrical energy by way of redox reactions.

When one of the formed products in an exhange reaction between an anion and a cation is a gas.

The phase of matter in which the particles have the biggest freedom of movement. Gases fill the whole space of the container in which it is kept.

A formula that fits all the members of a homologous series.

A device that converts mechanical energy into electrical energy by using Faraday's principle.

Generator that produces an alternating current (AC) because it has two split rings.

A region in space where a mass will experienece a gravitational force. The force field that exist around any body with mass and causes it to have an attraction force on another body with mass.

The attraction force between any two bodies due to their mass.

The energy an object posesses due to its posistion in the gravitational field relative to a reference point.

The state when the electrons occupy the loweste possible energy levels.

The pressure (p) of an enclosed mass of gas is directly proportional to the absolute temperature (T) at constant volume.

The industrial process to manufacture ammonia from nitrogen and hydrogen in the presence of a catalyst.

A half cell forms one half of a galvanic cell. It consists of an elctrode in a solution of its ions.

During a redox reaction two half reactions take place simultaneously - a reduction half reaction and an oxidation half reaction.

A carbohydrate in which one or more hydrogens are replaced with a halogen atom (F, Br, Cl or I )

An addition reaction where a halogen attaches to an unsaturated hydrocarbon.

(ΔH) The energy absorped or released during a chemical reaction.

The position and the energy of a subatomic particle cannot be determined simultaneously.

A heterogeneous mixture consist of substances that are in different phases, or out of components that can be identified individualy.

Reaction where the reagents and products are in different phases.

The catalyst and reagents are in different phases.

All the substances are in the same phase and the different components cannot be identified individualy.

Reaction where the reagents and products are in the same phase.

The catalyst and reagents are in the same phases.

A series of similar compounds that have the same functional group and the same general formula, but where each member differs from the previous member by a single -CH2-unit.

Electrons fill equal energy orbitals of a sub-shell with their spin in the same direction, before pairing takes place.

Each point on a wave front is the source of a new spherical wave. The superpositioning of all the small wavelets will form the new wave.

A compound that has a specific number of water molecules per formula unit - For example blue copper sulphate crystals.

The process when ions are surrounded by water molecules in a solution.

An addition reaction between water and an unsaturated hydrocarbon.

A compound where hydrogen is bonded to a metal.

An addition reaction between a hydrohalogen and an unsaturated hydrocarbon. The hydrocarbon becomes more saturated.

Compounds that consist only of carbon and hydrogen atoms.

An addition reaction between hydrogen and an unsaturated hydrocarbon (alkene or alkyne) in the presence of a catalyst (Ni, Pa, Pt) resulting in the organic compound becoming more saturated.

A substitution reaction where a haloalkane reacts with water to form an alcohol.

All the water on the earth.

A substance that attracts water.

An ideal gas is a hypothetical gas in which the gas molecules have a negligible volume and there are no attraction force between the particles of the gas. It conforms to the general gas equation in all respects.

The volume (V), pressure (p) and temperature (T) of a gas is determined by the amount of gas (n).

The product of the net force (Fnet) acting on an object and the contact time (∆t) that the force is acting on the object.

The product of the net force (Fnet) and the time (Δt) that the force acts on the object is equal to the change in momentum (Δp) of the object - (Δp = Fnet x Δt).

A substance consisting of more than one form of matter.

Points on a wave where the amplitude and direction of the disturbance are the same.

The variable that can cause a change in the dependent variable. On graphs it always appears on the x-axis. The values of the independent variableare selected before the experiement starts.

A chemical substance that has different colours in basic and acidic solutions.

A collision in which only momentum is conserved.

The property of an object that causes it to resist a change in its state of rest or uniform motion.

The speed at a specific moment and is equal to the magnitude of the instantaneous velocity at that moment.

A vector quantity of displacement divided by a very small time interval.

Interference occurs when two or more waves move across each other and effect each other.

Forces of attraction between molecules.

Van der Waals intermolecular attraction force between a polar molecule and a non-polar molecule in which a temporary dipole was induced.

Van der Waals intermolecular attraction force between two polar molecules.

A very strong intermolecular dipole-dipole attraction force between molecules consisting of hydrogen and another atom with a high electronegativity value, like oxygen, nitrogen and fluorine.

Intermolecular attraction force between an ion and a polar molecule.

Intermolecular attraction force that forms when an ion induces a dipole in a non-polar molecule.

Weak Van der Waals intermolecular attraction force. Unequal distribution of the electron cloud around big non-polar molecules lead to momentary dipoles forming.

Collective name for weak intermolecular forces arising from the interaction of moleculecular dipoles.

Forces which the objects within a specific system excert on each other.

Bonding forces between atoms within molecules (Interatomic forces).

When an increase in one variable leads to a decrease in the other variable.

An ion is a single atom or a group of atoms with a positive or a negative charge; eg. Na+ ; Br- ; NH4+ ; SO2-2

An electron(s) is transferred from one atom to another to form ions, with subsequent attractive electrostatic forces keeping them together.

A chemical reaction between a substance and water to form hydrated ions.

The minumum energy needed to remove the first electron from an atom in the gas phase.

A chemical reaction that can only take place in one direction. The reagents react to form the products, BUT the products cannot react with each other.

A system where the total mass of the system remains constant during a chemical reaction and NO energy transfer between the system and the surroundings can take place.

A system that does not interact with its surroundings, that is, its total energy and mass stay constant.

Molecules that have the same molecular formulae, but different structure formulae.

Atoms of the same element (same atomic number) but with a different mass number. (Number of protons in the nucleus are the same, but the number of neutrons in the nucleus is different).

The unit for Energy (E) or Work done (W). One Joule is the amount of work done on an object if a force of 1 Newton moves the object over 1 meter.

The SI unit for absolute temperature where the scale starts with 0 Kelvin.

Organic compounds with a carbonyl group (-C=O ) as a functional group in the middle of the carbon chain. The name of a ketone ends in -one.

Unit used for the consumption of electrical energy, indicating the electrical power (watt) consumed in 1 hour.

The energy an object posesses as a result of the object's motion(velocity).

The force that opposes the motion of a moving opject relative to the surface.

Describes the motion of atoms and molecules.

The energy required to make a substance change phases.

A chemical compound will always consist of the same elements and in the same mass ratios, irrespective of how it is prepared.

When light is reflected the angle of incidence (i) is always equal to the angle of reflection (r).

When the equilibrium in a closed system is disturbed (change in pressure, temperature or concentration) the system will re-instate a new equilibrium by favouring the reaction that will oppose the disturbance.

The process where certain substances are drained out of a bigger assembly by selectively dissolving them.

Hold the first finger, middle finger and thumb of the left hand perpendicular to each other. If the first finger indicates the direction of the magnetic field and the middle finger points in the direction of the current in the conductor, then the thumb will point in the direction of the force on the conductor.

When a changing magnetic field induces a current in a conductor, the direction of the induced current will be such that it produces a second magnetic field which will counter the original changing magnetic field.

The valence electrons around an atom or ion are shown as dots or crosses.

The speed of light is constant when passing through a given medium, but is different in different mediums.

The spectrum that is obtained when atoms from elements emmit their characteristic wavelengths.

A condensed state of matter where the particles have restricted movement and have the ability to flow. Liquids take on the shape of the container.

The outer layer of the earth, consisting of the crust and upper mantle.

Paired valence electrons which do not form part of the chemical bond.

Consecutive pulses where the disturbance is in the same direction as the wave.

An indication of the amount of work done per unit charge to overcome the internal resistance of the battery.

A molecule that consist of a large number of atoms.

An object with a pair of opposite magnetic poles, called North and South.

The region in space where a magnet or ferromagnetic material will experience a magnetic force (non-contact).

Schematic representation that is used to show the shape and direction of a magnetic field. The convention is that the direction of the magnetic field lines is the direction into which the N pole of a compass will show when it is placed in the field.

The number of magnetic field lines passing through a closed area. It is calculated as the product of the number of turns on the coil and the flux through the coil.

The magnetic flux density (magnetic field strength) is the magnetic force which a conductor will experience in a magnetic field if a current is flowing through the wire. The magnetic flux (F) passing through a loop of area A in the presence of a uniform magnetic field B, is F = BAcosθ, where θ is the angle between the magnetic field B and the normal to the loop A.

The space where the Earth's magnetic field will be experienced.

An apparatus that is used to measure the pressure of gases by measuring the different heights of a liquid in a U-tube.

When an unsymetrical reagent is added to an unsymmetrical alkene, the hydrogen will bond to the carbon with the greater number of attatched hydrogens and the X atom will bond to the more substituted carbon.

Die amount of matter (quantity of atoms or molecules) that a substance is made of.

Mass number (A) is the sum of the protons and neutrons in the nucleus of an atom.

The total mechenical energy is the sum of the potential and kinetic energy at a point.

The temperature at which a substance changes phases from solid to liquid (the solid phase and the liquid phase are in equilibrium).

Positive metallic atom rests are kept together by a sea of delocalised electrons swarming around them.

Substances with both metal and non-metal properties.

A mixture consist of various pure substances that does not react chemicallywith each other and which can be separeted with physical methods.

The mole (n) solute per volume of the solution.

Mass (m) in gram of one mole (n) of a substance.

1 mole of any gas occupies 22,4 cubic decimeters at STP.

The molar concentration of a substance and indicates the number of moles solute per volume of solution in dm3 .

The amount of substance that contains as many entities (6.022 x 1023) as there are atoms in 12g of carbon-12.

Gives the ratio and quantity of the atoms of each element in the molecule.

A neutral compound consisting of two or more atoms that are bound to each other with chemical bonds and which exist as a unit.

The product of the mass (m) and velocity (v) of an object.

Light of a single colour (wavelength).

Small organic molecules that can be bonded covalently to each other in a repeating pattern to form a polymer.

An acid that can donate only one proton (H+) per acid molecule.

The phenomenon that a current-bearing conductor experiences a force when it is placed in a magnetic field.

A catalyst that increases the activation energy of a reaction and therefore decreases the reaction rate.

A chemical reaction between an acid and a base to form a salt and water.

Sub atomic particle with no charge, found inside the nucleus.

An object continues in its state of rest or move a with constant velocity in a straight line, unless it is acted upon by an unbalanced (net or resultant) force.

Every object in the universe attracts every other object with a force (F) that is directly proportional to the product of their masses (m) and inversely proportional to the square of the distance (r) between their centres.

When a nett force (Fnet) is applied to an object of mass (m), the object will accelerate (a) in the direction of the nett force. The acceleration is directly proportional to the nett force and inversely proportional to the mass.

The net force (Fnet) acting in on an object is equal to the rate (∆t) of change in momentum (∆p) of the object in the direction of the resultant/net force.

When object A exerts a force on object B, object B simultaneously exerts a similar force on A which is of the same magnitude, but in the opposite direction. (Known as action-reaction pairs).

In a noble gas electron structure there are no unpaired or empty orbitals in the valence level of the atom.

Areas where no interference is visible due to destructive interference.

If the work done by a force to move an object between two points is dependent on the path of motion, the force is called non-conservative. The net work done by a non- conservative force to move an object around a closed path (starting and ending at same point) is NOT zero.

Forces that objects can exert on each other over a distance.

A condutor that does not obey Ohm's law. The ratio V/I is not constant (the current does not increase evenly with an increase in voltage).

Two atoms that are covalently bonded to each other. The bonding electron pair is shared equally between the two atoms.

Energy sources that are consumed quicker than they can be formed - Petroleum; Natural gas; Coal; Uranium; etc

A reaction that will not take place on its own. Some energy is needed to start the reaction and then it can continue on its own.

The magnitude of the electric field strength is not constant throughout the field and a charge will not experience the same force at every point in the field.

A magnetic field where the field strength and direction is different at different points in the field.

A perpendicular reaction force excerted by the surface on an object when that object is in contact with the surface.

Octahedral molecular form is obtained when four atoms form a central flat quadrant and the other atoms form two pyramids, one above and one below the central quadrant. The bonding angles are all 90°.

An atom (except hydrogen) will strive to form bonds with other atoms or ions until the nucleus is surrounded by 8 valence electrons.

Unit of electrical resistance. One ohm is the electrical resistance between two points in an electrical circuit if the potential difference between the points is one volt and the current flowing is one ampere.

A conductor that obeys Ohm's law. The ratio V/I is constant (the current increases evenly with an increase in voltage) at a constant temperature.

The current through a conductor is directly proportional to the potential difference across the conductor at constant temperature.

A system where energy and matter can be given to or be taken from the surroundings.

A circuit is open if an electric current cannot flow through the circuit.

The property of a medium that indicates to what extent the medium will restrain the speed of light.

Any medium through which light can propogate (move).

The region in an atom where the probability to find an electron is the highest.

Molecules that contain carbon atoms.

The chemical process for making nitric acid (HNO3)

Points on a wave where the amplitude and/or direction of the disturbance are not the same.

The loss of electron(s) by a molecule, atom or ion during a reaction.

The reagent that oxidizes the other reagents. In this process the oxidation agent itself undergoes reduction - gains electrons.

A number indicating the number of electrons that an atom in a compound has lost or gained during a reaction.

The half reaction in which the reagent loses electrons (is oxidised). The oxidation number of that reagent will increase.

A parallel circuit allows the current to go through different branches at the same time.

The unit for pressure. A pressure of 1 Pa is exerted on a surface if a force of 1N acts on an area of 1 square meter.

There can be maximum two electrons per orbital on the condition that their spin is opposite. No two electrons of an atom can have the same quantum numbers.

A numerical scale representing an atom's tendency to pull the bonding electron pair closer to itself (electronegativity scale).

The time it takes to complete one full cycle of a wave. The inverse of frequency ( T = 1/f).

The pH scale is an indication of the relative acidity of the solution. It is calculated by using the concentration of the hydronium ions in the solution.

When the forward and reverse phase changes take place at the same rate (are in balance).

An electron which is released from the surface of a metal when the metal is irradiated by electromagnetic radiation of a frequency larger than the treshold frequency.

The ejection of electrons from certain metals when they are exposed to light with a specific frequency.

The energy parcel (quantum) of electromagnetic radiation that moves with the speed of light, but has no mass.

A physical change is a temporary change which does not alter the chemical nature of the substance - no new chemical substances are formed.

No new substances are formed. The substance only changes phase.

A molecule where the bonding electrons are not shared equally between the atoms. The shift of the electron pair towards one of the atoms leads to the formation of a dipole.

A large molecule composed of smaller monomer units bonded covalently in a repeated pattern.

A chemical process where monomers bond covalently to each other to form a polymer.

An acid that can donate two or more protons per acid molecule.

Position is always taken relative to a reference point. Can be positive or negative.

Molecules with the same molecular formula, but the functional group or side chain is in a different position.

A catalyst that decreases the activation energy of a reaction and therefore increases the reaction rate.

The difference in electrical potential energy between two points. It is determined by the work done to move a charge from the one point to the other point.

The rate at which work is done, or the rate at which energy is transfered..

When two solutions are added together and one of the formed products is insoluble it forms a solid precipitate.

The force exerted per unit area (1 Pa = 1 N/m²)

The new substances that form when the reagents react with each other during a chemical reaction.

An object onto which the only force that acts in on it is gravitational force.

A chemical reaction in which proton (H+) transfer takes place.

Sub atomic positively charged particle found inside the nucleus of an atom.

A single energy disturbance.

A pure substance consist of only one form of matter with spesific physical and chemical properties and fixed composition.

In any right angled triangle the square of the hypotenuse is equal to the sum of the squares of the other two sides.

Any charge in the universe are multiples of the elementary charge (charge of an electron).

Emmision of energy and/or particles from an unstable atomic nucleus to create a more stable atomic nucleus.

The change in the concentration of reagents or products per unit time.

A sketch showing the path of a light ray through different media.

The chemicals that react with each other when the reaction starts.

The area of a reagent that can come into contact with the other reagents for a reaction to occur between them.

In a real gas the molecules have volume which contribute to the volume of the gas and there are force interactions between the molecules. At extreme conditions a real gas deviates from the universal gas equation.

Doppler effect. A shift in the longer wavelengths (red end of spectrum) when a light source moves away from the observer.

A reaction in which electron (e-) transfer takes place from one chemical substance to another chemical substance and therefore the oxidation numbers of the participating atoms will change.

The reagent that reduces the other reagents. In this process the reduction agent itself undergoes oxidation - loses electrons.

The gaining of electrons by a molecule,atom or ion during a reaction.

The half reaction in which the reagent gains electrons (is reduced). The oxidation number of that reagent will decrease.

Refraction index of a transparent medium is the ration of the speed of light in a vacuum (v₁) to the speed of light in that medium (v₂).

The changing of the direction of light as it passes from one optical medium to another medium with a different optical density.

The mass of an atom relative to the mass of a carbon-12 atom.

The sum of the atomic masses of all the atoms in a molecule of the substance and is measured in atomic mass unit (u).

Energy derived from natural resources that are not used up - Hydropower; Geothermal; Wind; Solar; Biomass; etc

The solid precipitate that remains after filtration.

The characteristic of matter to resist the flow of an electric current if a potential difference is applied across it.

An electrical component that is designed to resist the flow of an electric current.

A single vector quantity that has the same effect as the other vectors combined

A chemical reaction in which the reagents react to form products and then the products react to form the original reagents.

Hold the first finger, middle finger and thumb of the right hand perpendicular to each other. If the first finger indicates the direction of the magnetic field and the thumb the direction of movement, then the middle finger will give the direction of the induced conventional current.

If you bend the fingers of your right hand in the direction of the conventional current, then your stretched thumb will indicate the direction of the induced magnetic field.

If you hold the solenoid in your right hand with your bent fingers in the direction of the conventional current, then your stretched thumb will point in the direction of the N-pole of the solenoid.

Hold the conductor in your right hand with the thumb pointing in the direction of the conventional current. The direction in which the fingers curl, indicates the direction of the magnetic field (field lines).

The RMS current, Irms for an alternating current (AC) is equal to the direct current (DC) current that uses the same amount of energy as the alternating current.

The RMS potential difference, Vrms for an alternating current (AC) is equal to the direct current (DC) potential difference that uses the same amount of energy as the alternating current.

A method to calculate the effective values of an alternating voltage or alternating current, taking into account that they continually change from a positive maximum through zero to a negative maximum. (The average will be zero).

A sustance in which the hydrogen of an acid is replaced by a cation

A hydrocarbon chain in which all the bonds between C-atoms are single bonds.

A solution in which an excess solute has been dissolved in the solvent.

A physical quantity that has magnitude only - time, mass, length, volume, energy, charge, temperature, etc.

A substance that can only conduct electicity under certain specific conditions. Used for the control of electric currents in electronics.

In a series circuit the current has to flow through all the components one after the other.

When light passes from a medium with refraction index n₁ to another medium with refraction index n₂ the relationship between the angle of incidence (θ₁) and the angle of refraction (θ₁) is : n₁sin θ₁ = n₂sinθ₂

A solenoid consist of a large number of coils of conducting wire that are wound into a unit. When a current flows through it, it creates a magnetic field.

The most dense phase of matter where particles are bonded to each other. Solids retain their shape irrespective of the container.

The amount of solute that can dissolve in the solvent at a specific temperature.

The substance that is dissolved in the solvent to form a solution.

The final mix of solute in the solvent.

The liquid substance into which another substance is dissolved to form a solution.

The amount of energy required to increase the temperature of 1 gram of a substance by 1 °C.

A scalar quantity for the rate of change in distance.

A component in the electric motor that reverses the current in the coil every half cycle to ensure that the torque continue acting in the same direction.

A reaction that will take place on its own (spontaneously).

The potential difference between a specific half cell and the standard hydrogen half cell.

The electrode used as standard to determine the redox potentials of other elements.

A solution of which the concentration is known.

To standardise a solution means you use a solution with known consentration to determine the consentration of the unknown solution.

An equilibrium where no further changes occur, not on micro or macro level.

The force relative to the surface that opposes the attempts to bring a stationary object into motion.

Standard reference conditions - Standard temperature = 0 °C (273 K); Standard pressure = 1 atmosphere (101,3 kPa)

An acid that ionises completely in water to form a high concentration of hydronium ions.

A base that dissosiates/ionises completely in water to form a high concentration of OH- ions.

Shows how the atoms in a molecule are linked to each other. All bonds are shown as lines between the atoms.

Very small particles that make up an atom.

A phase change where a substance changes directly from a solid into a gas without going through a liquid phase.

A reaction in which an atom or group of atoms in a saturated hydrocarbon is substituted by another atom or group of atoms to form a different saturated hydrocarbon and a byproduct.

The addition of the amplitudes of two pulses that occupy the same space at the same time.

A heterogenuous mixture where solid particles float in a liquid.

The production of more complex chemical compounds when simpler substances react.

A line that touches a curve tangentialy at one point

The temperature of a substance is an indication of the average kinetic energy of the particles in the substance.

The force that is exerted through an object that can stretch (rope, wire, spring).

The constant final velocity that a falling object attains when the downward gravitational force is equal to the upward air resistance.

Tetrahedral molecular form is obtained when four atoms are bonded to a central atom with bonding angles of 109,5° each.

A material that does not allow heat energy to be transferred easily through it.

The minimum frequency (energy) of light required to release an electron from the surface of a material (E = hf).

An experimental procedure where a liquid with known concentration is used to detrmine the unknown concentration of another liquid.

Total internal reflection occurs when light moves from an opticaly more dense to an opticaly less dense medium and the angle of incidence is greater that the critical angle.

Consecutive pulses where the particles of the medium (energy disturbances) move perpendicular to the propagation direction of of the wave.

If three forces in the same plane acting in on the same point are in equilibrium, then their magnitudes and directions can be represented as the sides of a closed triangle when they are placed in sequence.

Trigonal bipyramidal molecular form is obtained when three atoms form an even side triangle (angles 120°) in a flat plane, with a fourth atom above the plane to form a pyramid. The bond angle between the fourth atom and the plane is 90°.

Trigonal planar molecular form is obtained if three atoms in a flat plane bond to a central atom. The bond angle between these atoms and the central atom is 120°.

Covalent bond where two atoms share 6 electrons (three electron pairs).

An acid that can donate three protons per acid molecule.

Sound with frequencies between 20 kHz and 100 kHz.

The magnitude of the electric field strength is constant throughout the field and a charge will experience the same force at every point in the field.

A magnetic field where the field strength and direction is constant at all the points in the field.

Motion in a straight line where the speed of the object remains constant (no acceleration).

A valence electron that is available to be shared to form a chemical bond.

Compounds with one or more multiple bonds between C atoms in the hydrocarbon chain.

A closed space with no matter in it.

The number of electrons that can take part in a reaction.

The electrons in the outer main energy level of an atom.

The pressure exerted by a vapour at equalibrium with its liquid in a closed system.

A physical quantity with both magnitude and direction - displacement, weight, force, magnetic field strength, etc.

A vector quantity for the rate of change of displacement.

A measure of a liquids ability to flow.

A potential difference of 1 V means that 1 joule of work is done per coulomb of charge. ( 1 V = 1 J/ C) 

A voltmeter measures the potential difference between two points in a circuit. It is always connected in parallel.

The unit for power. One watt (W) is the amount of power used to do work(energy transfer) of 1 joule in 1 second.

A wave is consecutive pulses where the particles of the medium move in the direction of the energy disturbance, but does not move along with the wave.

The maximum positive disturbance of a particle from the rest/equilibrium position.

The product of frequency (f) and wavelength (ג) of a wave (v = f x λ ).

The maximum negative disturbance of a particle from the rest/equilibrium position.

Light exhibits properties of both particles and waves. The particle nature explains the photo-electric effect, while the wave nature explains diffraction and interference.

The wavelength (ג) of a soundwave is the distance between two consecutive compressions or rarefactions (expansions).

The wavelength (ג) of a lightwave is the distance between two consecutive points that are in phase (eg. crest to next crest)

An acid that ionises incompletely in water to form a low concentration of hydronium ions)

A base that dissociates incompletely in water to form a low concentration of OH- ions.

The gravitational force that the earth excerts on any object on or near its surface.

The work (w) done on a object by a constant force F, is F∆xcosθ, where F is the magnitude of the force, ∆x the magnitude of the displacement and θ the angle between the force and the displacement.

The minimum amount of energy (Wₒ) needed to emit an electron from the surface of a metal.

The net work done by a resultant/net force on an object is equal to the change in the kinetic energy of the object .

A measure of the extent of the reaction, by comparing the amount of the reagents consumed against the amount of product that formed.

At dehidrogenation or dehalogenation, if more than one product is formed, the main product will be the alkene with the highest subsitituted chain. (The H will be removed from the C-atom with the fewest H-atoms.)