Teaching Science Glossary



Pangaea: The name given to the supercontinent that consisted of all Earth’s landmasses.
parallel circuit: An electric circuit that contains more than one conducting path.
parsec: The distance from which one astronomical unit would subtend 1 s of arc. A parsec equals 3.26 light-years.
pascal (Pa): A unit of pressure. 1 Pa is 1 N (newton) of force per square metre.
pegmatite: A coarse-grained igneous rock usually of granite composition.
penumbra: A region of partial shadow.
perigee: The closest point in an elliptical orbit.
perihelion: The point of orbit closest to the Sun of a body orbiting the Sun.
period: A horizontal row of the periodic table.
periodic table: An arrangement of elements in order of increasing atomic number; the start of a new period corresponds to the outer shell electron of that element beginning a new shell.
persistent organic pollutant (POP): A synthetically made chemical that is dangerous to animals and/or the environment.
petrochemical: A chemical extracted from crude oil.
photosphere: The region of the Sun from which most light is emitted.
pH scale: A measure of the concentration of hydronium ions in an aqueous solution. pH less than 7 is a base, pH greater than 7 is an acid and pH = 7 is a neutral solution.
physical change: A reversible change in a material (e.g. a change of state).
physical property: A characteristic of a substance that can be observed or measured that does not change how the substance looks.
pitch: A quantity used by musicians that is related to the frequency of sound.
plasma: A very hot state of matter in which electrons have been stripped from atoms to leave positively charged ions (nuclei), which mingle freely with the electrons.
plastic: A substance that can be moulded into different shapes.
plastic behaviour: This is when a substance gets stretched to the point it is permanently stretched or deformed.
plate: The section of the lithosphere that moves over the asthenosphere.
plate tectonic theory: The theory that suggests the lithosphere is made up of plates that move on the asthenosphere.
plutonic rock: Intrusive igneous rock.
polar molecule: A molecule that has one part with a negative charge and another part with a positive charge.
polar orbit: An orbit that takes in the poles of the planet, moon or sun being orbited.
poly-atomic ion: A molecule that has an overall electric charge.
polymer: A large molecule, usually with a chain-like structure made from smaller, similar chemical units called ‘monomers’.
polymerisation: The process of forming a polymer.
polymerises: This is where a substance forms long molecular chains.
positive charge: The charge on a proton or a charge on a substance that has fewer electrons than it has protons.
potential energy: Stored energy. For example, a stretched rubber band has potential energy as it has the ability to fire a projectile; an object raised to a specific height has gravitational potential energy as it has the ability, if let go, to fall with kinetic energy.
power: The rate of energy that is transformed. For a battery, the power is the amount of energy being transformed from chemical energy to electrical energy each second. For a load, the power is the amount of energy that is transformed to other energies every second. Power is measured in watts.
power rating: Most domestic electric appliances, when operating normally, have a specified power that is indicated on the appliance. The power rating assumes that the input voltage is 240 V (volts).
precession: The wobbling of Earth’s axis.
precipitation: Forms of water that fall from clouds (i.e. rain, hail and snow).
pressure: A quantity that represents the amount of force per unit area that is applied to an object. Pressure is measured in pascals (Pa) where 1 Pa is 1 N (newton) per square metre.
pressure pattern: Usually associated with the representation of sound waves. The pressure pattern shows areas of high and low pressure. This is normally seen on a cathode ray oscilloscope (CRO).
primary colours of light or pigments: With the three primary colours of light or pigments, all the other colours that humans see can be perceived. The primary colours of light are red, green and blue. The primary colours of pigments are magenta, yellow and cyan. The primary colours of light are the secondary colours of pigments and vice versa.
products: The compounds produced by a chemical reaction.
proton: A positively charged particle found in the nucleus of an atom.
pulsar: A celestial object that gives off pulses of electromagnetic radiation.
pure substance: A substance that contains the same type of atom or molecule (i.e. either an element or a compound).
P wave: A primary wave. A seismic longitudinal wave that is the fastest of the seismic waves.
pyroclastic materials: Substances in fragments, such as ash, explosively ejected from a volcano.

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