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Hormone: A chemical substance produced in a living organism which controls the rate of biochemical processes.

Hermann Grid Illusion: This is an optical illusion named by ‘Ludimar Hermann’ in the 1800’s. The illusion is characterised by blobs perceived at the intersections of a light-coloured grid between black squares.

Hering Illusion: This is an optical illusion named by Ewald Hering. The vertical or horizontal lines are all straight, but look as if they were bent. The distortion is produced by a lined pattern on the background that simulates a perspective design and creates a false impression of depth.

Helium: Helium is the chemical element with atomic number 2 and an atomic weight of 4.0026, which is represented by the symbol He. Helium is a colourless, odourless and tasteless gas. It also makes up a small amount of the air we breathe. It originates from the Greek word ‘helios’ meaning the sun. Helium is commonly used as a cooling agent in superconductors, cryogenics, inflating balloons as well as inflating airships.

Heat: A form of energy that is transferred by a difference in temperature.

Gyroscopic effect: Having the effect of a gyroscope – a rotating mechanism mounted so that its axis can turn freely in one or more directions. A spinning gyroscope tends to resist change in the direction of its axis.

Grounding: The process of connecting equipment to a common ground or ‘earth’. This is done as a safety mechanism in order to avoid the unsafe energizing of equipment.

Gravity: The force of attraction between all masses in the universe, especially the attraction of the earth’s mass for bodies near its surface. The farther a body from the earth’s surface, the less the gravitational force acting on it.

Grafting: A method of plant breeding widely used in agriculture and horticulture, where the tissues of one plant are encouraged to fuse with those of another.

Golden section: A mathematical or geometrical proportion where the ratio between a small section and a larger section is equal to the ratio between the larger section and both sections put together.

Germination: The process whereby seeds or spores sprout and begin to grow

Genetically engineered plants: The alteration of the genome of plants grown for food in order to produce crops with specific advantages.

Gear: A toothed wheel that engages another toothed mechanism in order to change the speed or direction of transmitted motion.

Galvanometer: A type of ammeter or instrument for detecting or comparing or measuring small electric currents.

Galileo: Galileo Galilei was an Italian astronomer and mathematician who was the first to use a telescope to study the stars; demonstrated that different weights descend at the same rate; perfected the refracting telescope that enabled him to make many discoveries (1564-1642).

Fuse:  Also called a ‘fusible link’ is a type of over current protection device. It consists of a metal wire or strip that melts when too much current flows, which interrupts the circuit in which it is connected.

Fungus: An organism of the kingdom ‘Fungi’ lacking chlorophyll and feeding on organic matter.

Fulcrum: The pivot about which a lever turns

Friction: The interaction between surfaces: a measure of the resistance felt when sliding one body over another.

Fezing point: The temperature at which a liquid changes state and forms a solid.

Fluid: A fluid is a substance that continually deforms or ‘flows’. All gases and most liquids are considered to be fluids. The main characteristic of a fluid is that they are capable of flowing and easily changing shape.

Float: To be afloat either on or below a liquid surface and not sink to the bottom of the liquid.

Fire extinguisher: Any of various portable steel container devices for spraying and extinguishing a fire with Carbon dioxide or other chemicals.

Fingerprint: An impression of the underside of the end of a finger or thumb. It is used for identification because the arrangement of ridges in any fingerprint is thought to be unique and permanent with each person.

Filament: A thin wire in a light bulb that is heated white hot by the passage of an electric current. Tungsten is often used.

Ferrites: A magnetic material containing powdered iron oxide (Fe2O3) which usually has magnetic properties. Ferrous Of or relating to or containing iron. Metals that contain iron as the major alloying elemen

Fat: A soft greasy substance occurring in organic tissue and consisting of a mixture of lipids.

Exothermic reaction: A chemical reaction in which heat is given off during the formation of new chemical compounds.

Evaporation: The process of a liquid converting to the gaseous state. Evaporation is a type of vaporization of a liquid, which occurs only on the surface of a liquid.

Evaporate: The opposite of ‘condensate’. The transition from a liquid state into a gaseous state.

Eutrophication: A process by which an excess of plant nutrients, for example nitrogen and phosphorous, reduces the oxygen dissolved within a body of water, producing an environment that does not readily support aquatic life.

Ethylene: Ethylene is an organic gas compound with the formula C2H4. This gas is produced by fruits and vegetables that is rotting and accelerates the ripening and aging process of nearby fruits.

Equilateral triangle: In an equilateral triangle all sides have the same length and the same angles each measuring 60 degrees

Enzyme: Complex proteins produced by cells that facilitates or speeds up certain bio-chemical reactions in the body.

Emulsifier: A chemical that can bind two incompatible items, such as oil and water.

Electrons: Tiny particles with a negative charge that are capable of creating an electrical current.

Endothermic reaction: A chemical reaction accompanied by the absorption of heat.

Emulsifier: A chemical that can bind two incompatible items, such as oil and water.

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Embryo: A minute rudimentary plant contained within a seed.

Electroscope: A simple device that detects the presence of an electric charge by the mutual repulsion of metal foils.

Electromagnet: An electromagnet is a type of magnet whose magnetic field is produced by the flow of electric current. The magnetic field disappears when the current ceases.

Electrolyte: An electrolyte is any liquid that is able to conduct electricity. Salt water makes an excellent conductor.

Electrolysis: The process by which we generate hydrogen and oxygen from water is called electrolysis.

Electrical current: Electrical current is the flow of charged electrons through a circuit. Electrical current, which is electrons flowing in a wire, can be explained as cars driving along a road, where the road is the wire and the cars are the electrons. The current would be the number of cars passing a given point.

Electric meter: A device that measures the amount of electrical energy consumed by a residence, business, or an electrically powered device.

Electric generator: A device that converts mechanical or kinetic energy to electrical energy. The reverse conversion of electrical energy into mechanical energy is done by a motor; motors and generators have many similarities.

Elastomer: Any polymer having the elastic properties of rubber.

Elastic energy: Potential energy that is stored when a body is deformed as in a coiled spring or elastic band

Eddy-current: Circulating movement of electrical current within an electrical conductor caused by the intersection of the conductor with a moving magnetic field.

Eclipse: An eclipse is an astronomical event that occurs when one celestial object moves into the shadow of another.

Echo-sounding: Determining the location of something by measuring the time it takes for an echo to return from it.

Echo-location: Determining the location of something by measuring the time it takes for an echo to return from it.

Echo: The repetition of a sound resulting from reflection of the sound waves.

Dye: A usually soluble substance for staining or colouring e.g. fabrics or hair.

Downforce: The downward pressure created by the aerodynamic characteristics of a car that allows it to travel faster through a corner by increasing the pressure between the contact area of the tire and the road surface, thus creating more grip.

Dominant eye: Also known as Ocular dominance is the tendency to prefer visual input from one eye to the other. It is somewhat similar to being right or left handed. The side of the dominant eye and the dominant hand do not always match.

DNA: Deoxyribonucleic acid is a long linear polymer found in the nucleus of a cell and formed from nucleotides and shaped like a double helix. DNA is associated with the transmission of genetic information or all living organisms and some viruses.

Dissolving: Solid matter reduced to a liquid form that has been disintegrated in a solvent.

Displacement: Displacement occurs when an object is immersed in a fluid, pushing it out of the way and taking its place.

Diopter: A unit of measurement of the refractive power of a lens, which is equal to the reciprocal of the focal length measured in meters.

Diffusio: The process by which a substance moves from an area of high concentration, through a barrier or membrane, to an area of lower concentration.

Dextrin: Dextrin is obtained by hydrolysis of starch. It is a tasteless, odourless gummy substance that is often used as a thickening agent, in adhesives and in dietary supplements.

Dew point: The temperature at which the water vapour in the air becomes saturated and condensation begins. Dewpoint is expressed as a temperature in degrees Fahrenheit or Celsius.

Detergent: A detergent is a material intended to assist cleaning. The term is sometimes used to differentiate between soap and other surface-active chemical cleaning agents widely used in industry and laundering.

Desiccant: A substance that promotes drying.

Density: The amount of matter contained by a given volume. The symbol of density is ρ (the Greek letter rho)

Dehydration: Dryness resulting from the removal of water.

Creep: Creep is the tendency of a solid material such as soil, to slowly move or deform permanently under the influence of certain forces.

Convex / Concave: Curving or bulging outward or inward.

Convection: The transfer of heat through a fluid (liquid or gas) caused by molecular motion. In the atmosphere, convection usually refers to the vertical movement of air masses. An example of convection is the rising of warm surface air and the sinking of cold air from upper levels of the atmosphere.

Conductor: A material that has enough free electrons to allow an electrical current to flow when a potential difference is applied. Conductors are usually metallic in nature, but not always, such as graphite for example.

Conduction: The movement of heat through a material as kinetic energy is transferred from molecule to molecule. The handle of an iron pan on the stove gets hot due to heat conduction.

Condensation: Condensation is the process by which matter transitions from a gas (or vapour) phase into a liquid phase. Dew forming on grass in the morning is a common example of condensation.

Condensate: The opposite of ‘evaporate’. The transition from a gaseous state into a liquid state.

Colour spectrum: The distribution of colours produced when light is dispersed by a prism. The order is displayed in the following order: Red, Orange, Yellow, Green, Blue and Violet.

Cohesion: Cohesion is a physical property of a substance, caused by the intermolecular attraction between like-molecules within a body or substance that acts to unite them.

Cocoon: The silky protective case spun by the larvae of some insects and moths in which they metamorphose.

Cobalt chloride: A chemical substance often used to predict the presence of water molecules within the air or other substance.