Teaching Science Glossary



dangerous goods: A hazardous chemical that needs to be handled with care.
decantation: A technique for separating mixtures that involves pouring the liquid substance(s) off a solid that has settled on the bottom of a container.
decibels: A quantity used to measure the loudness of sound.
declination: The celestial latitude on the celestial sphere, measured in degrees north or south of the celestial equator.
density: The amount of mass of a substance per given volume of space the substance takes up. Its units are kg/m3.
deposition: A change of state from a gas to a solid.
depositional environment: A geographical area where sediment accumulates.
detergent: A chemical used for cleaning. It assists non-polar substances to dissolve in water. Detergents are surfactants.
detrital sedimentary rock: Sedimentary rock that consists of solid particles of pre-existing rocks.
diatomic molecule: A molecule that contains two atoms covalently bonded.
diffuse reflection: The reflection of light off non-mirrored surfaces. A beam of light diffusely reflects off non-mirrored surfaces in all directions.
diffusion: A process whereby two substances mix thoroughly. This usually occurs in solid-liquid, liquid-liquid and gas-gas mixtures.
dilute solution: A solution with a small quantity of solute.
dilution: Adding a solvent to a solution to reduce its concentration.
diode: A device in an electric circuit that allows a current to pass through it in only one direction.
dipole: A bond between two atoms where one atom is slightly negatively charged as it attracts the bonding electrons more than the other atom.
dipole–dipole bonding: Bonding between molecules.
dispersion: A refraction effect where white light is split up into its constituent colours. The colours of the spectrum.
distillation: The separation of a liquid from a solid or other liquid by heating, causing evaporation, followed by cooling, causing condensation.
domain: A region within a material where the particles have an aligned magnetic field.
double bond: A double covalent bond between two atoms in a molecule.
drag: Air-resistance force.
dry cell: An electrochemical cell that does not contain electrolytes in liquid.
ductility: A physical property of a material with the ability to be drawn into a thread.
durability: The ability of a substance to last.

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