# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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earthing: This is when a charged object shares its charge with a much larger object, such as Earth. The charged object loses most, if not all, of its charge to the larger object. In doing so the object discharges.
earthquake: Vibrations caused by the sudden release of energy, usually as a result of the displacement of rocks along faults.
echo: Sound that is reflected off an object.
eclipse: The hiding of one celestial body by another.
ecliptic: The path followed by the Sun across the celestial sphere in the course of a year.
effort: The input force to a machine.
effort distance: Distance traversed by the input force of a machine.
elastic behaviour: The property of a substance to return to its original shape after stretching or compression.
elastic potential energy: The ‘energy of position’, such as when objects are stretched or compressed (e.g. bows and springs). The elastic potential energy is greatest at greatest stretch or greatest compression of the elastic substance.
elasticity: The ability of a substance to be stretched and return to its original state.
elastomer: A material that returns to its original position after contraction or expansion (e.g. rubber). Elastomers undergo elastic behaviour.
electrical conductivity: The ability of a substance to carry an electric current.
electrical energy: The energy that is delivered from a battery and transformed in a load (e.g. in a bulb). Energy supplied by batteries or generators and carried by electric charges in electric circuits.
electrical force: A field force that acts on an object that has an overall charge.
electrical potential energy: The ‘energy of position’ between two charged objects. The electrical potential energy between two oppositely charged objects is greatest at maximum separation.
electric charge: A quantity that is the property of sub-atomic particles. An electron has a negative charge and a proton has a positive charge. Charge is measured in coulombs.
electric circuit: A continuous conducting path for electric charges, from the positive terminal of a battery to the negative terminal of the battery and back to the positive terminal of the battery.
electric current: A flow of electric charges in a conductor.
electric field: A region in space where electric charges will be forced to move. Charged objects create electric fields around them.
electrochemical cell: A redox reaction that produces an electric current.
electrodes: Conductors where reduction and oxidation occur in an electrochemical cell.
electrolyte: A substance which, in the liquid state or in an aqueous solution, will conduct an electric current.
electromagnet: A device that has a large magnetic field when a current passes through it. An electromagnet is made of a coil of wire, usually around an iron core, that is connected to a battery or generator.
electromagnetic energy: Energy that travels through space at the speed of light and is produced by accelerating electric charges. There are various energy types, such as radio waves, infra-red radiation, visible light, X-rays and gamma radiation.
electromagnetic radiation: Radiation that travels at the speed of light and comes in different energies. Low-energy electromagnetic radiation is called ‘radio waves’ and high-energy electromagnetic radiation is called ‘gamma radiation’. Electromagnetic radiation is sometimes simply referred to as light. It is a wave phenomenon caused by changing electric and magnetic fields.
electromagnetic spectrum: The range of energies of electromagnetic radiation. In order from lowest energy to highest energy, the spectrum is made up of radio waves (FM radio and UHF TV), microwaves, infra-red radiation, visible light, UV light, X-rays and gamma radiation.
electron: A negatively charged particle that moves around the nucleus of an atom.
electron-dot diagram: A Lewis diagram that shows the arrangements of valence electrons in an atom.
electronegativity: The ability of an atom that is bonded to another atom to attract the bonding electrons toward itself.
electronic configuration: The arrangement of electrons in energy levels or shells within an atom.
electron shell: Regions of energy levels surrounding the atom, where electrons reside.
electron shell diagram: A diagram that shows the symbol of the element surrounded by increasing circles (that represent shells) with dots to represent the location of electrons in shells.
electrostatic force: A push or a pull on electric charges that interact. Attraction occurs between ‘unlike’ charges and repulsion occurs between ‘like’ charges.
electrostatic separation: A technique for separating mixtures. One constituent of the mixture is electrically charged and attracted to another electrically charged object.
element: A substance composed of atoms with the same atomic number, which means that the atoms have the same number of protons within their nuclei.
ellipse: Oval shape.
empirical formula: A formula of a compound that shows the elements present and their ratio. For example, the empirical formula for water is H2O.
emulsifier: A substance added to stabilise the suspension of one liquid in another, reducing the tendency for the two liquids to separate. Emulsifiers are surfactants.
emulsions: Tiny droplets of one liquid suspended in another liquid.
endothermic reaction: A chemical reaction that takes heat energy from the environment.
energy: An object with energy has the ability to change or move another object. Energy is measured in joules.
energy level: A region that surrounds the nucleus of an atom, in which electrons are located.
enhanced greenhouse effect: The pollution of the atmosphere has led to a greater greenhouse effect, leading to global warming.
enthalpy: The total kinetic and potential energies of the atoms within a substance.
enzyme: A catalyst located within the body that increases the rate of chemical reactions that occur there.
epicentre: The point on Earth’s surface vertically above the focus of an earthquake.
equilibrium: The state of a chemical reaction where the rate of the forward reaction equals the rate of the reverse reaction.
equinox: An intersection of the ecliptic and the celestial equator. When the Sun is at this point, Earth experiences equal length day and night.
evaporation: A change of state from a solid or liquid to a gas.
event horizon: The sphere around a black hole from which nothing can escape.
exothermic reaction: A chemical reaction that releases heat energy to the environment.
extrusive igneous rock: Igneous rock formed at the surface of Earth.