washing soda – Washing soda is a common name for the compound sodium carbonate (Na₂CO₃).
Also known as: sodium carbonate, alkali soda, soda ash

water – Water is a chemical compound consisting of two hydrogen atoms and one oxygen. The name water typically refers to the liquid state of the compound. The solid phase is known as ice and gas phase is called steam.
Also known as: dihydrogen monoxide, hydrogen hydroxide, H₂O

water gas – Water gas is a combustion fuel containing carbon monoxide (CO) and hydrogen gas (H₂). Water gas is made by passing steam across heated hydrocarbons. The reaction between steam and hydrocarbons produce the water gas mixture. Water gas used in the synthesis of some industrial processes.

water of crystallization Water of crystallization is water that is stoichiometrically bound into a crystal. Crystal salts containing water of crystallization are called hydrates.
Also known as: water of hydration, crystallization water
Examples: Commercial root killers often contain copper sulfate pentahydrate (CuSO₄·5H₂O) crystals. The five water molecules are called water of crystallization.

water of hydration – another name for water of crystallization.

water softener – A water softener is a compound that lowers the hardness of water by ion exchange to precipitate out hard mineral ions from the water. Examples: Sodium carbonate is a water softener. Sodium carbonate dissociates in water into sodium and carbonate ions. The ‘hard’ water’s calcium and magnesium ions attach themselves to the carbonate ions and precipitate out.

watt – Watt is the SI unit for power.
1 Watt (W) = 1 Joule/second (J/s)

wavefunction – A wavefunction is a function describing the probability of a particle’s quantum state. This function is expressed as a probability of a particle’s position, momentum, time, and/or spin. Wavefunctions are commonly denoted by the variable Ψ.
Also known as: wave function

wavelength – Wavelength is a property of a wave that is the distance between identical points between two successive waves. The distance between one crest (or trough) of one wave and the next is the wavelength of the wave. The symbol for wavelength is the lower case Greek letter lambda ( λ ).
Example: The wavelength of light determines its color and the wavelength of sound determines the pitch.

wavenumber – Wavenumber is the number of waves per unit length. Wavenumber is the reciprocal of a wave’s wavelength. Wavenumbers are used extensively in spectroscopy.

wave-particle duality – Wave-particle duality describes the properties of photons and subatomic particles to exhibit properties of both waves and particles.

wax – Wax is a lipid made up of a chain molecule comprised of alkanes or esters derived from alcohols and fatty acids.
Examples: beeswax, paraffin

weak acid – A weak acid is an acid that only partially dissociates into ions in an aqueous solution.
Examples: acetic acid (CH₃COOH), formic acid (HCOOH), citric acid (C₆H₈O₇)

weak base – A weak acid is a base that only partially dissociates into ions in an aqueous solution.
Examples: ammonia (NH₃), ammonium hydroxide (NH₄OH), ethylamine (CH₃CH₂NH₂)

weak electrolyte – A weak electrolyte is an electrolyte that does not completely dissociate in solution. The solution will contain both ions and molecules of the electrolyte.
Examples: acetic acid (HC₂H₃O₂), carbonic acid (H₂CO₃), ammonia (NH₃) are all weak electrolytes.

wedge-and-dash projection – Wedge and dash projection is a drawing of a molecule showing the bonds between atoms in a molecule. The lines representing the bonds come in three forms:

1. solid lines to represent bonds which are in the plane of the paper
2. dashed lines to represent bonds that extend into the plane of the paper, and
3. wedge-shaped lines to represent bonds oriented towards the viewer.

weight – Weight is the name of the force exerted on an object due to the acceleration of gravity.

wet – In chemistry, wet is when a surface is coated with a layer of liquid. Wet also applies to a process where water or a liquid is present.

wetting – Wetting is the ability of a liquid to maintain contact or ‘stick’ to a solid surface. Wetting is also the process of applying a thin layer of liquid to a solid surface.

white body – A white body is an idealized material that reflects all incident electromagnetic radiation. White body is the opposite of a black body.

white vitriol – White vitriol is an old name for the compound zinc sulfate (ZnSO₄).

wismuth – Wismuth is an old name for the element bismuth.

witherite – Witherite is the compound barium carbonate (BaCO₃) in mineral form. Witherite is sometimes used as a rodenticide.

wolfram – Wolfram is an alternate name for the element tungsten. Wolfram is the origin of tungsten’s symbol, W.

wood alcohol – Wood alcohol is an alternate name for the organic alcohol methanol.
Also known as: methanol, methyl alcohol, wood spirits, hydroxymethane, methyl hydrate, carbinol

wood ether – Wood ether is an alternate name for the compound dimethyl ether (CH₃OCH₃). Wood ether or dimethyl ether is the simplest ether molecule.
Also known as: dimethyl ether, DME, methoxymethane

Wood’s metal – Wood’s metal is an alloy consisting of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by weight. This alloy is used when a low-temperature melting point is needed such as the metal in fire suppression sprinklers. The sprinkler contains Wood’s metal that will melt when exposed to fire and releases the water.

wood spirits – Wood spirits is an old name for the organic alcohol methanol.

word equation – A word reaction is a chemical reaction expressed in words rather than chemical formulas.
For example, the chemical reaction 2 H₂(g) + O₂(g) → 2 H₂O(g) would be expressed as hydrogen gas + oxygen gas → steam or “hydrogen and oxygen react to form water”.

work – Work is the energy required to move an object against a force. Work is equal to the force times the distance the object moves in the direction of the force. The SI unit for work is the joule.

working solution – Working solution is a name given to a chemical solution made for actual use in a lab. Working solutions are usually made by diluting or combining stock or standard solutions.

woulfe bottle – A Woulfe bottle is a piece of glassware used to pass gases through a liquid. Woulfe bottles have two or three necks to attach tubing for the gases.

Wurtz reaction – The Wurtz reaction is the coupling of two alkyl halide molecules to form an alkane.