Teaching Science Glossary



latent heat: The amount of energy that is absorbed or released during a change of state. During melting or boiling a substance requires energy from neighbouring objects to change state. During condensation or freezing an object transfers energy to the surrounding objects. A change of state occurs at the same temperature.
lattice: The scaffolding arrangement of atoms within a crystal.
lava: Magma at Earth’s surface.
lever: A rigid bar that rotates about a fixed point called a ‘fulcrum’.
Lewis diagram: A diagram that shows the arrangement of valence electrons in an atom.
lift: The upward force on an object in flight.
light: Electromagnetic radiation. Light can be produced in many ways and at different energies.
light-dependent resistor (LDR): A device used in electric circuits that varies in its resistance depending on the amount of light that falls on it. In the dark an LDR has high resistance and in light conditions it has low resistance.
light-emitting diode (LED): A diode that lights up when a current passes through it.
light energy: Sometimes called ‘electromagnetic radiation’ and considered to be pure energy that can be absorbed by atoms to move them.
lightning: An atmospheric spark effect where there is movement of electrons between clouds or between a cloud and the ground.
light-year: The distance light travels in 1 year.
liquid: A state of matter where atoms or molecules are held loosely. A liquid needs a vessel in order to be contained.
lithification: This is where sediment is converted into sedimentary rock.
lithosphere: The outer, rigid part of Earth, consisting of the upper mantle and crust. It lies above the asthenosphere.
litmus: A natural dye that changes colour in an acid (red) and a base (blue).
load: A component of an electric circuit that transforms electrical energy into other forms of energy.
load distance: The distance traversed by the output force of a machine.
load force: The output force of a machine.
local group: The two dozen or so galaxies, including the Milky Way, that form a subcluster.
lone-pair electrons: Pairs of valence electrons that do not bond.
longitudinal wave: A disturbance through a material where the particles in the material vibrate forward and backward as the disturbance moves forward.
loudness: A measure in sound pressure waves of how large a vibration is. Loudness is measured in decibels.
luminosity: The amount of energy given off by an object per unit time.
lunar eclipse: The passage of the Moon into Earth’s shadow.
lustre: The appearance of a rock surface after reflection by light. Lustre can be metallic or non-metallic.

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