Water (molecule) in the context of "Heavy water"

A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, and biochemistry, the distinction from ions is dropped and molecule is often used when referring to polyatomic ions.

A molecule may be homonuclear, that is, it consists of atoms of one chemical element, e.g. two atoms in the oxygen molecule (O₂); or it may be heteronuclear, a chemical compound composed of more than one element, e.g. water (two hydrogen atoms and one oxygen atom; H₂O). In the kinetic theory of gases, the term molecule is often used for any gaseous particle regardless of its composition. This relaxes the requirement that a molecule contains two or more atoms, since the noble gases are individual atoms. Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are typically not considered single molecules.

Thermohaline circulation (THC) is a part of the large-scale ocean circulation driven by global density gradients formed by surface heat and freshwater fluxes. The name thermohaline is derived from thermo-, referring to temperature, and haline, referring to salt content—factors which together determine the density of sea water.

Wind-driven surface currents (such as the Gulf Stream) travel polewards from the equatorial Atlantic Ocean, cooling and sinking en-route to higher latitudes - eventually becoming part of the North Atlantic Deep Water - before flowing into the ocean basins. While the bulk of thermohaline water upwells in the Southern Ocean, the oldest waters (with a transit time of approximately 1000 years) upwell in the North Pacific; extensive mixing takes place between the ocean basins, reducing the difference in their densities, forming the Earth's oceans a global system. The water in these circuits transport energy - as heat - and mass - as dissolved solids and gases - around the globe. Consequently, the state of the circulation greatly impacts the climate of Earth.

Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that determine the position of each atom.

Molecular geometry influences several properties of a substance including its reactivity, polarity, phase of matter, color, magnetism and biological activity. The angles between bonds that an atom forms depend only weakly on the rest of a molecule, i.e. they can be understood as approximately local and hence transferable properties.

Toluene (/ˈtɒl.juiːn/), also known as toluol (/ˈtɒl.ju.ɒl, -ɔːl, -oʊl/), is a substituted aromatic hydrocarbon with the chemical formula C₆H₅CH₃, often abbreviated as PhCH₃, where Ph stands for the phenyl group. It is a colorless, water-insoluble liquid with the odor associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH₃) attached to a phenyl group by a single bond. As such, its systematic IUPAC name is methylbenzene. Toluene is predominantly used as an industrial feedstock and a solvent.

As the solvent in some types of paint thinner, permanent markers, contact cement and certain types of glue, toluene is sometimes used as a recreational inhalant and has the potential of causing severe neurological harm.

Hydrogen cyanide (also called prussic acid) is a chemical compound with the formula HCN and structural formula H−C≡N. It is a highly toxic and flammable liquid that boils slightly above room temperature, at 25.6 °C (78.1 °F). HCN is produced on an industrial scale and is a highly valued precursor to many chemical compounds ranging from polymers to pharmaceuticals. Large-scale applications are for the production of potassium cyanide and adiponitrile, used in mining and plastics, respectively. It is more toxic than solid cyanide compounds due to its volatile nature. A solution of hydrogen cyanide in water, represented as HCN(aq), is called hydrocyanic acid. The salts of the cyanide anion are known as cyanides.

Whether hydrogen cyanide is an organic compound or not is a topic of debate among chemists. It is traditionally considered inorganic, but can also be considered a nitrile, giving rise to its alternative names of methanenitrile and formonitrile.