Glossary of Chemical Terms as Encountered in the Laboratory of Chem 121/123 at UBC

All definitions written, compiled, or modified by Dr. Matthew Le Page of UBC.  Source material is: My head. Zumdahl, Steven. Chemical Principles, 3rd ed., New York: Houghton Mifflin Company, 1998.  Mortimer, Charles. Chemistry, 6th ed., Belmont: Wadsworth Publishing Co., 1986.  Curriculumvisions.com at the following URL: http://www.curriculumvisions.com/Elements/ElementsGlossary.html  Dictionary.com at the following URL: http://www.dictionary.com/

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Note that no Organic Chemistry terms are included in this Glossary.

Absorb:(verb) The collection of one substance within another substance. Examples: visible light being absorbed by a dark liquid, garlic odor being absorbed into a glass of milk, radar being absorbed into the special paint on a stealth jet, a chemical spill being absorbed into a sponge.  A pie thrown into the mouth of a clown is absorbed by the clown.  Compare to "adsorb".

Absorbance:(noun) The amount of light absorbed by a liquid sample in colorimetric analysis.  The initial amount of light (I_o) shone at a liquid sample will decrease as it passes through the sample because it is absorbed by the chemicals within. The amount of light that re-emerges (I) will be less than I_o.  Mathematically, absorbance (A) = log (I_o/I); no units.  Using Beerâs Law, absorbance = edc.

Absorption spectrum: (noun) A plot of wavelength (x-axis) versus absorbance (y-axis) obtained from colorimetric analysis when polychromatic light is used.

Acid buffer capacity: (noun) The number of moles of acid (ie, H₃O⁺ or H⁺) that will lower the pH of a buffer solution by one pH unit.

Acid-base indicator: (noun) A substance that marks the endpoint of an acid-base titration by changing colour.  Most commonly encountered indicator is phenolphthalein which is pink under basic conditions and colourless under acidic conditions.

Acidic conditions:  (adjective) When the pH of a chemical system is less than 7.

Acid Dissociation Constant:  see "K_a".

Acidic solution: (adjective) When the pH of a liquid is less than 7; is usually aqueous.

Acidic to litmus: (adjective) This phrase means that a liquid substance, usually aqueous, will turn blue litmus paper red, thus indicating that the pH of the liquid is less than 7 and thus acidic.

Acidosis:(noun) The human condition that occurs when the pH of the blood drops below 7.35.

Accurately: (adverb) Any action relating to quantitative analysis that is performed in such a manner to allow the maximum number of significant figures to be obtained.  In other words, not a single atom of the substance should be lost during the action.  When "accurately transferring a solution" one must first use a pipetand then rinse all of the glassware used with deionized water and pour the rinsings into the flask that is receiving the solution so as to transfer every single atom.  In the phrase "accurately weigh", one would be required to use an analytical balance.

ACS format:(noun) "American Chemical Society" citation format for referencing papers.  Written as: author last name (alphabetized), initial. initial.; author last name (alphabetized), initial. initial.; Journal abbreviated name. year, volume (issue number if applicable), first page number.  Example: James, B.R.; Le Page, M.D. Chem. Commun. 2000, 16, 1647.

Adaptor:(noun) A small device used to attach either a sintered glass crucible or a Buchner funnel to a vacuum filter flask. 

Adsorb:(verb) The collection of one substance on the surface of another, usually by electrostatic or van der Waals forces.  Examples: dust adsorbed on a table; garlic odor being adsorbed onto a jacket.  A pie thrown at the face of a clown is adsorbed by the clown.  Compare to "absorb".

Adsorbent:(noun) A substance that is used to adsorb another substance onto its surface.  The stationary phase in chromatography.  In thin layer chromatography, the paper of the chromatographic plate is the adsorbent.  In column chromatography, a substance such as silica gel is the adsorbent.

Adsorption:see "Adsorb".

Air bleed: (noun) A small clamp that is attached to the rubber hose in a vacuum filtration setup.  Opening the air bleed allows air into the vacuum filtration setup, thus reducing the suction power of the vacuum. 

Aliquot: (noun) A portion or sample of a solid or liquid substance.  For example, if you squeeze an orange and get 300 mL of juice, and then take 25 mL of the juice to analyze for Vitamin C content, the 25 mL portion is known as an aliquot.

Alkali:(noun) Alkali metal; the elements Li, Na, K, Rb, Cs, Fr.  Synonymous with "basic".

Alkaloids:(noun) Any of various organic compounds, normally with bases and usually containing at least one nitrogen atom in a heterocyclic ring, occurring chiefly in many vascular plants and some fungi.  Many alkaloids, such as nicotine, quinine, cocaine, and morphine, are known for their poisonous or medicinal attributes.

Alkalosis: (noun) The human condition that occurs when the pH of the blood rises above 7.45.

Alligator clip: (noun) A spring-loaded clip with serrated jaws, often used to make temporary electrical connections. 

Analysis: (noun) A systematic investigation in which a specific property of a substance is examined.  Example: weighing a diamond (the substance) is a type of analysis that leads to knowledge of the mass (a property) of the diamond.

Analyst:(noun) A person who performs an analysis.

Analytical balance: (noun) An electronic scale that can measure the mass of an object to an accuracy of ± 0.0001 grams. 

Analytical weighing: see "Weighed accurately".

Anhydrous: (adjective) Lacking water; water has been removed.  Also called "dry".

Anion:(noun) A negatively charged ion.

Anode:(noun) The negatively charged terminal of an electrochemical cell that is supplying current.

Aqua Regia:(noun) A corrosive, fuming mixture of hydrochloric and nitric acids capable of dissolving metals such as platinum and gold.

Aqueous: (adjective) A solution in which the solvent is water.  Example: an aqueous solution of sodium hydroxide would be NaOH(aq).

Base buffer capacity: (noun) The number of moles of base (ie, OH^-) that will raise the pH of a buffer solution by one pH unit.

Basic conditions: (adjective) When the pH of a chemical system is greater than 7.

Base Dissociation Constant:  see "K_b".

Basic solution: (adjective) When the pH of a liquid is greater than 7; is usually aqueous.

Basic to litmus: (adjective) This phrase means that a liquid substance, usually aqueous, will turn red litmus paper blue, thus indicating that the pH of the liquid is greater than 7 and thus basic. 

Beaker: (noun) A glass container used for holding liquids; comes in many volume sizes and glass thicknesses. 

Beaker tongs: (noun) An oversized pair of tweezers used for picking up a hot beaker so that one does not burn oneâs hands.

Beerâs Law: (noun) A = edc.  Used in colorimetric analysis.  States that the (A) of a liquid sample will equal the product of the molar absorptivity coefficient (e), the distance that the light must travel through the sample (d), and the concentrationof the solution (c).  This equation is commonly used to calculate the concentration of a liquid sample by measuring the sampleâs absorbance with a colorimeter.  The units of e, d, and c all cancel out such that A is unitless.

Blank: (noun) A sample used to calibrate an instrument.  A buffer solution of pH 7 would be used as a "blank" to calibrate a pH probe; distilled water would be used as a "blank" to calibrate a colorimeter; ice water at 0° C would be used as a "blank" to calibrate a temperature probe; a 100.000 gram mass of pure platinum would be used as a "blank" to calibrate an analytical balance.

Boiling point: (noun) The temperature at which a liquid changes into a gas.  Boiling points change with atmospheric pressure.  Example: the boiling point of pure water at standard atmospheric pressure is 100° C, but in a vacuum it will boil at room temperature.

Boiling water bath: (noun) A large (400 or 600 mL) beaker of water that is boiling on either a hotplate or with a Bunsen burner flame.  A smaller beaker or test tube containing the chemical to be heated is then lowered into the boiling water with either beaker tongs or a test-tube clamp. 

Break the vacuum: (verb) This phrase means that the air bleed on a vacuum filtration setup should be opened to reduce, or completely negate, the suction power of the water pump.  Once the vacuum has been "broken", the water pump can be safely turned off and the filter vessel detached from the vacuum filtration setup. 

Buchner flask: see "Filter flask".

Buchner funnel: (noun)A plastic or ceramic funnel which has a flat perforated disc on which filter paper can be placed. It is attached to a filter flask and used in vacuum filtration. 

Buffer: (noun) A solution that resists a change in pH when small amounts of an acid or base are added.  A buffer consists of an acid component and a base component, each of which will react to the addition of either a base or an acid, respectively.  Addition of acid will convert the base buffer component to its conjugate acid, thus maintaining a constant pH.  Similarly, addition of base will convert the acid buffer component to its conjugate base, again resulting in the pH remaining constant.

Buffer capacity: (noun) A term used to quantify a bufferâs power to resist pH changes.  The acid buffer capacity is defined as the number of moles of acid that can be added to one litre of buffer and resulting in the bufferâs pH dropping by 1 pH unit.  The base buffer capacity is defined as the number of moles of base that can be added to one litre of buffer and resulting in the bufferâs pH rising by 1 pH unit.

Buret: (noun) A long glass tube with volume markings running down the side and a stopcock (tap) at one end.  A buret is used vertically, with the stopcock at the bottom.  Its main use is as a reservoir for a chemical (the titrant) during titration.

Buret clamp: (noun) A metal clamp used to hold a buret in the vertical position. 

Calibration graph: (noun) A graph that is used to determine an unknown value.  Example: In a colorimetry experiment, a chemist would prepare, say, 5 solutions of aqueous Cu(SO₄)₂, each with a different concentration, and then scan each sample with a colorimeter to determine the absorbance of each sample.  The chemist would then plot a graph of concentration vs. absorbance.  This is the calibration graph.  The chemist could then scan the absorbance of a sample of Cu(SO₄)₂ of unknown concentration, and from the reading and the calibration graph, calculate what the actual concentration is.

Calibration marks: (noun) The line painted or etched into the glass on a pipet or a volumetric flask that indicates the exact level to which the implement should be filled with liquid. 

Capillary pipet: (noun) A glass tube with a very small diameter (ex, 0.5 mm) used for transferring tiny amounts (microlitres) of liquid.  A capillary pipet has a small enough diameter to allow surface tension effects to retain liquid within the tube. 

Capillary tube: see "Capillary pipet".

Carcinogen: (noun) A cancer-causing substance or agent.

Carrier phase: (noun) The liquid that is used to elute a mixture of chemicals during a chromatography experiment.

Cathode: (noun) The positively charged terminal of an electrochemical cell that is supplying current.

Cation: (noun) A positively charged ion.

Cell potential: (noun) The electric potential (in units of volts) required to move an electron from the anode to the cathode in a galvanic cell.  The symbol for cell potential is "E_cell".

Cell voltage: (noun) The measured voltage or cell potential of an electrochemical cell or galvanic cell.  Example: the cell voltage of a AA battery is 1.5 V.

Centrifuge: (1) (noun) A mechanical device for spinning small mixed samples very rapidly.  The fast spin causes the components of the mixture that have a different density to separate.  This has the same effect as filtration.   (2) (verb) The act of centrifuging.

Centrifugation: (noun) The technique of using a centrifuge to separate different components of a liquid sample.  Example: human blood can be separated into its various components by centrifugation.

Centrifuging: (verb) The act of using a centrifuge.

Characteristic: (adjective) A feature that helps to identify, tell apart, or describe recognizably a specific chemical.   Example: a garlic smell is characteristic of dimethyl sulfoxide; a rotten egg smell is characteristic of H₂S; a brilliant blue colour is characteristic of CuSO₄; a melting point of 191° C is characteristic of Vitamin C; a density of 0.788 g/mL is characteristic of acetone.

Charge neutrality: (noun) When two items have an opposite, but equal, electrical charge, they are said to be in "charge neutrality".  This term is usually applied to electrochemical cells.  Sometimes the addition of a third, charged chemical is required to maintain the charge neutrality.  Example: dissolved NaCl is charge neutral because the "+" of the Na cation is cancelled out by the "-" of the Cl anion.  If, however, the Cl^- anions combine to form Cl₂ gas, then the solution will be left with an overabundance of "+" charge (the Na cations) as the Cl₂ gas will leave the beaker.  To maintain charge neutrality, an additional source of electrons, such as OH^-, must be added to the solution.

Chemical system: (noun) That part of nature that is being investigated.  A collection of chemicals, forces, and laboratory equipment, all interacting with each other, and comprising a unified whole.  Example: if you are heating 300 mL of 1 M HCl(aq) in a beaker on a hotplate, and using a thermometer to measure the temperature and a pH probe to measure the pH, you could say that "the chemical system being investigated at 70° C has a pH of 2."

Chromatogram: (noun) The pattern of separated substances obtained on a chromatographic plate once it has been developed.

Chromatographic chamber: (noun) The beaker within which a chromatogram is developed.  The beaker contains a few mL of the solvent to be used as the carrier phase, and the chromatographic plate is then stood upright in the beaker, leaning against the inner wall.  A watch glass is placed over the beaker to cover it and prevent the solvent from evaporating

Chromatographic plate: (noun) A small sheet of glass or aluminum, coated on one side with the substance that makes up the stationary phase in a chromatography experiment.  The substance used can be, for example, silica gel or Al₂O₃, and is usually white in color and feels like chalk.  In paper chromatography, the paper can serve as both the material of which the plate is constructed and the stationary phase.

Chromatography: (noun) A separation technique using the ability of surfaces to adsorb substances with different strengths.  The mixture to be separated is first dissolved in a suitable solvent, and then a tiny amount (microliters) of this liquid, no bigger than a spot, is placed onto a chromatographic plate using a capillary pipet (this is known as "spotting" the plate).  The plate is then placed into a chromatographic chamber (beaker) which already contains the solvent that will be used as the carrier phase.  The carrier phase then slowly climbs up the plate, and as it does so, it reaches the spot of sample. The carrier phase then picks up the sample and continues to rise up the plate.  As the carrier phase moves along the stationary phase (the plate), the various substances within the sample will adsorb to the stationary phase at different strengths.  The substances with the least adherence to the surface move faster and leave behind those that adhere more strongly.  Once the carrier phase has reached the top of the plate, the plate is removed from the chamber and the solvent is allowed to evaporate off of the plate.  Visual inspection of the plate should reveal several spots at different locations along the plate, with each spot being a different chemical substance from within the original mixture. 

Clay triangle: (noun) A small triangle made of steel rods that are coated in ceramic to withstand heat. A clay triangle can be placed on a ring stand to hold a beaker, and heat can then be applied to the beaker from below using a bunsen burner.  A clay triangle can also be used to holda separatory funnel in an upright position.  Clay triangles are not used that much anymore, as chemists usually heat beakers directly on an electric hotplate instead of with a bunsen burner. 

Cold finger: (noun) A small test tube that is filled with ice/ice-water.  This test-tube is then placed into a vacuum filter flask that has been fitted with a rubber stopper.  During sublimation, the hot chemical vapours condense onto the cold finger, depositing a pure, solid layer of the chemical being sublimed. 

Colorimeter: (noun) A simple instrument used to measure the absorption of coloured light by a liquid sample.  When coupled with a computer, this device generates an absorption spectrum.  The more concentrated the sample, the greater the amount of absorption.

Colorimetric analysis: (noun) A specific type of spectroscopic analysis where the wavelength of the radiation being used is in the visible-light region of the electromagnetic spectrum.  This type of analysis can be used to determine both the identity and the quantity of chemicals within a liquid sample.  For example, performing colorimetric analysis on purple food-dye might reveal that it is actually composed of blue and red food-dyes in a 3:1 ratio.

In colorimetric analysis, a beam of polychromatic light is first shone through a liquid sample.  Various chemicals within the liquid will absorb certain wavelengths of the light and an absorption spectrum is generated by a computer.  Comparison of this spectrum to those of known chemicals allows one to identify the chemicals present within the liquid sample.  A second colorimetric analysis is then performed, this time at just the one specific wavelength of visible light (monochromatic) that is characteristic of the chemicals that are being examined in the liquid sample.  Using a calibration graph and Beerâs Law, the exact concentration of the chemical can then be calculated from the absorbance value.  The greater the concentration of the chemical within the liquid sample, the greater will be the absorbance reading. 

Colorimetric: (adjective) Being related to colorimetric analysis.  Any analysis that involves the colour of a substance.

Completeness of precipitation: (adjective) This phrase means that a chemist should test to see if all of a substance that was dissolved has now precipitated.  Quite often, when a substance is highly soluble, only a fraction of it will precipitate when the precipitating agent is added.  By adding more precipitating agent, one can see if more precipitate forms or not.  If none forms, it can be assumed that all of the substance has precipitated out of solution. 

Complex: see "Complex ion".

Complexes: (1) (noun) The plural form of complex. (2) (verb) The act of forming a complex.  Example: ammonia complexes copper ions to form Cu(NH₃)₄²⁺.

Complex ion: (noun) A charged compound consisting of a metal ion bonded to other chemicals. Example: Cu(NH₃)₄²⁺

Concentration: (noun) The amount of a substance dissolved in a certain quantity of solution and given the S.I. definition of moles per litre.  Abbreviated as "molar" and given the symbol "M".  Also written as [ ].  Example: [HCl(aq)] means "concentration of aqueous HCl".

Confirming reaction: (noun) A chemical reaction where the observed colour change (or lack thereof), or the formation of a precipitate (or lack thereof), either confirms the presence or the absence of a certain chemical.  Used in qualitative analysis to reveal the identity of what elements are present.  Example: the presence of silver in an aqueous mixture of unknown metal ions is confirmed if a white precipitate forms when HCl is added to the mixture.  The white precipitate is AgCl.

Conical funnel: (noun) An implement having a small hole or narrow tube at the bottom, and a much wider mouth at the top.  The shape resembles that of a cone.  A funnel can be made of glass, plastic, or metal and is used to channel the flow of a liquid substance into a small-mouthed container. 

Conjugate acid: (noun) The compound formed when a proton is added to a base.  Example: CH₃COOH (aq) is the conjugate acid of CH₃COO ^-(aq).

Conjugate base: (noun) What remains of an acid molecule after a proton is lost. Example: CH₃COO ^-(aq) is the conjugate base of CH₃COOH (aq).

Conjugate pair: (noun) Also called a "conjugate acid-base pair".  Two chemicals related to each other by the loss or gain of a single proton. Example: NH₄⁺ and NH₃.

Control sample: (noun) A sample used as a standard of comparison in an experiment.  Example: A chemist wishes to examine the effect of X-ray radiation on the Vitamin C content of Minute Maid orange juice.  The chemist would take a sample (say, 50 mL) of the orange juice and determine its Vitamin C content.  The chemist would then take another 50 mL sample of the orange juice and expose it to X-rays of a certain energy for a certain period of time.  The chemist would then determine the Vitamin C content using the same method as was used on the control sample.  The chemist would then compare the results for the two samples and be able to state with absolute certainty the effect of X-rays on the Vitamin C content of the orange juice.

Corrode: (verb) To destroy a substance (usually a metal) gradually by a chemical action (eg, oxidation).  Corrosion is often an unwanted chemical reaction, such as when marble statues are destroyed by pollution / acid rain or when a car rusts as the metal is oxidized by road salt during winter.

Corrosive: (adjective) A chemical that has the ability to corrode another substance.

Creep: (verb) The act of a liquid substance rising up a glass surface due to surface tension forces.  This phenomenon allows capillary pipets to be used to hold liquids, but also unfortunately drives material out of the top of a filter funnel.

Cuvet: (noun) A rectangular test-tube used to hold the liquid sample in colorimetric analysis.  A cuvet is made from special glass or plastic that will not absorb any light itself so as not to hinder the colorimetric analysis.  As silicate glass and certain plastics will not absorb light in the 375 ö 2000 nm wavelength range, these materials are commonly used to make cuvets for use in colorimetric analysis.  Quartz cuvets must be used for analysis done in the ultraviolet wavelength range (300 nm). 

Decant: (verb) The act of pouring out a liquid, usually with the intent of leaving some of the liquid behind in the original container.  The act of decanting can also involve pouring the liquid portion off of the top of a precipitate that has settled to the bottom of a beaker.

Dehydrating agent: (noun) Any substance that will remove water from another substance.  Example: powdered anhydrous NaSO₄, when added to an organic liquid that contains water, will form solid clumps of hydrated NaSO₄ as it locks away the water molecules.  Filtration of this mixture will yield a water-free (dried) organic liquid.

Dehydration: (verb). The removal of water from a substance by heating it, placing it in a dry atmosphere (such as a desert) or using a drying / dehydrating agent.  See "Drying".

Deionized: (adjective) A term used to describe water which has had all trace contaminant ions removed from it to yield pure water.  Is sometimes call "distilled water" or "DI water". The water obtained from a Brita filter is deionized. Bottled water, such as Polar Springsä is not deionized as it contains many supposedly nutritionally beneficial ions.

Develop: (verb) The act of eluting a chromatographic plate.  Once the elution is complete, the plate is said to have been "developed".

Dilution: (verb) The process of adding solvent to lower the concentration of solute in a solution.  Example: adding 500 mL of water (solvent) to 100 mL of dissolved NaCl (solute) results in a lowering of the concentration of the NaCl.

Dilution factor: (adjective) In the above example under "Dilution", there is a dilution factor of 5.

Diprotic: (adjective) A chemical that has two hydrogen ions to donate to bases in an acid-base reaction.  Example: sulfuric acid, H₂SO₄, is diprotic, because it can donate two protons to become SO₄^2-.

Discharge: (verb) To release something.  This could be, for example, the discharge of liquid from a buret or of electricity from a battery.

Dissociation: (noun) The process by which a compound body (ie, molecule) breaks up into simpler constituents.  The act of breaking bonds apart, and resulting in the ionization of the compound body.  Example: the dissociation of ammonium chloride (NH₄Cl) into hydrochloric acid (HCl) and ammonia (NH₃).  In the case of acids, dissociation results in the formation of hydrogen ions.  Strong acids dissociate completely. Weak acids are not completely ionized, and a solution of a weak acid has a relatively low concentration of hydrogen ions.

Dissolve: (verb) The act of breaking down a substance in a solution without causing a chemical reaction.  Example: NaCl(s) is broken down into Na⁺ cations and Cl^-anions in water, but does not react with the water.

Distilled water: see "deionized water".

Distillation: (noun) The separation of a mixture of liquid chemicals (ie, solution) into its components by heating the solution in a special flask until one of the components boils.  The hot vapours then rise until they encounter a cold section of the flask, upon which the vapours instantly condense and drip into a collecting flask.  The temperature inside the flask will not rise until all of that component has boiled off.  The temperature then rises until it reaches the boiling point of the second component, at which time a new collecting flask is used to capture this second chemical.  This process can be continually repeated until all the liquid components within the flask have been separated, as long as they all have boiling points that differ from each other by at least 5° C.  Example: a mixture of acetone, methanol, ethanol, and water can be separated by distillation as the boiling points for the four components are 57, 65, 79, and 100° C, respectively.

Dried: (adverb) Having had all water removed from a substance.  See "Drying".

Dropper: (noun) A small glass tube with a rubber suction bulb at one end for drawing liquid into the tube and releasing it out a drop at a time.  Also called an "eye dropper". 

Dropping pipet: (noun) A special kind of dropper the screws into the top of a small bottle.  It is used to transfer out small amounts of whatever chemical is in the bottle. 

Dry: (adjective) see "Anhydrous".

Drying: (verb) Any action that removes water from a substance. This could involve heating a solid in an oven at a temperature above 100° C, or rinsing a solid with ethanol to remove the water, or adding a dehydrating agent, such as NaSO₄, to an organic liquid to remove the water. 

Drying agent: see "Dehydrating agent".

e: see "Molar absorptivity coefficient".

E°: see "Standard electrode potential".

E°_cell: see "Standard cell potential".

E_cell: see "Cell potential".

EDTA: (noun) Acronym for ethylene diaamine tetraacetate (C₁₀H₁₆N₂O₈).  This large organic compound binds to many different metal ions and prevents them from reacting with any other chemical that might be present in solution.  The injection of EDTA(l) into a personâs arteries is an excellent means by which toxic metals within the bloodstream can be rendered harmless.

Electric eye: see "Photogate".

Electric potential: (noun) The energy produced by an electrochemical cell and measured by itâs voltage or electromotive force.

Electric potential difference: (noun) The amount of electric potential between the anode and the cathode of an electrochemical cell.  The greater the potential, the greater the driving force upon the electrons within the cell.  The potential is measured in units of volts with a volt meter and abbreviated with the symbol "E".

Electrical lead: (noun) A conductor by which one circuit element is electrically connected to another.

Electrochemical cell: (noun) A cell consisting of two electrodes and an electrolyte.  It can be set up to generate an electric current (usually known as a galvanic cell, an example of which is a battery), or an electric current can be passed through it to produce a chemical reaction (in which case it is called an electrolytic cell and can be used to refine metals or for electroplating).

Electrochemical series: (noun) A list of the relative values of the electric potential (E) measured for a group of substances that are either oxidizing agents or reducing agents.  Those substance that are oxidizing agents have positive E values, while those that are reducing agents will have negative E values.  Once the E value has been measured for each substance, the list is constructed with the greatest positive E value substance at the top of the list, and the greatest negative E value substance at the bottom of the list.  A standard electrochemical reaction must first be chosen as the reference point for all of these measurements, and this standard is assigned an E value of zero.  In many cases, the reaction chosen is: 2H⁺ + 2e^-® H₂.

Electrochemistry: (noun) The study of the interchange of electrical and chemical energy.

Electrode: (noun) An electrical conductor that forms one terminal of a cell; can be either an anode or a cathode.

Electrolyte: (noun) An ionic solution that conducts electricity.  This is one of the two routes by which the anode and the cathode of an electrochemical cell exchange electrons.

Electrolytic cell: (noun) An electrochemical cell where current is passed through to produce a chemical reaction.  Such a cell can be used to refine metals.

Electromotive force: (noun) The force set up in an electric circuit by the potential difference between the anode and the cathode of an electrochemical cell.  This is abbreviated as "emf", and is often taken as a measure of the tendency for an oxidation-reduction reaction to occur.

Elevated temperature: (adjective) A qualitative phrase that means "high temperature".

Elute: (verb) To extract one material from another by means of chromatography.  The carrier phase is the chemical solvent that elutes the mixture of materials being separated by chromatography. 

emf: see "Electromotive force".

Emulsion: (noun)A mixture of tiny droplets of one liquid in a second liquid with which the first will not mix.  Emulsions often form when two immiscible liquids are vigorously shaken up in a container.  It can take many hours before an emulsion disperses back into the original state of two completely separated liquids.  Examples: an emulsion of oil in vinegar or CH₂Cl₂ in water. 

Endothermic reaction: (noun) A reaction where energy flows into a system, that is, energy (as heat) is consumed.

Endpoint: (noun) The point in a titration when the indicator changes colour.  This does not always happen at the equivalence point, depending on which indicator is used.  In a reaction between an acid and a base, the endpoint is also sometimes called the "neutralization point".

Equilibria: (noun) The plural form of "equilibrium".

Equilibrium: (noun) The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the reactants and products does not change with time.  A double-headed arrow () is used to signify an equilibrium, as opposed to the single-headed arrow (®) used for a reaction that has gone to completion (ie, 100%).

Equilibrium constant: (noun) Abbreviated as "K".  The number obtained from the equilibrium expression of a reaction in equilibrium.  If K > 1, then the concentrations of the products is greater than the reactants and the forward reaction is said to be favoured.  If K < 1, then the concentrations of the reactants is greater than the products and the reverse reaction is said to be favoured.  If K = 1, then neither side of the reaction is favoured over the other side.

Equilibrium expression:(noun) The equation obtained by multiplying the concentrations of the products and dividing by the multiplied reactant concentrations.  Example: for the chemical reaction A + 2B  C + D, the equilibrium expression is ([A][B]²) /([C][D]).  If A=0.5, B=2, C=1, and D=3, then the equilibrium constant (K) = 0.667.

Equivalence point: (noun) The point in a titration when the two reactants are present in stoichiometrically equivalent amounts.  The number of moles of the titrant added equals the number of moles initially present of the chemical being titrated.

Erlenmeyer flask: (noun) A glass container which has a narrow, cylindrical mouth and a cone-shaped main body that ends in a wide, flat bottom.  It is most often used in titrations to hold the liquid that is being titrated. 

Etched line: (noun) The line engraved into the glass on a pipet or volumetric flask that indicates the exact level to which the implement should be filled with liquid. 

Evaporation: (noun) The process by which any substance is converted from a liquid state to a gaseous state, and carried off as a vapour.  Evaporation begins to happen below the boiling point.

Exothermic reaction: (noun) A reaction where energy flows out of the system, that is, energy (as heat) is created.

Experimental errors: (noun) Events that reduce the accuracy to which an experimental result can be reported.  The two types of experimental error are Indeterminate and Determinate Errors.  Indeterminate errors (or random errors) cause data to be scattered symmetrically around an average value that is close to the accepted value, whereas determinate errors cause the average value obtained from a set of readings to differ significantly from the accepted value.  The three main sources of Determinate Error are: (1) Instrument Errors, caused by imperfections in measuring devices and instabilities in the power supplies, (2) Method Errors, which arise from non-ideal chemical or physical behaviour of analytical systems, (3) Human Errors, which result from the carelessness, inattention, or personal limitations of the experimenter.  Most experimental errors encountered in first-year chemistry labs are of this last type.

Extraction: (noun) The process of obtaining something from a mixture by chemical, physical, or mechanical means. Examples of extractions include filtrations, distillations, and sublimations.

Filter: (1) (verb) To perform a filtration.  (2) (noun) The membrane used in a filtration.  Examples include filter paper and sintered glass crucibles. 

Filter flask: (noun) A flask made of thick glass designed to withstand the changes in pressure that occur when the arm of the flask is connected via a rubber hose to a suction pump. 

Filter funnel: (noun) Any type of funnel used in a filtration.  Examples include conical funnels, Buchner funnels, and sintered glass crucibles.

Filter paper: (noun) The disk of paper used in a filtration.  Example: a coffee filter.

Filter trap: (noun) A second filter flask that is connected between the water pump and the primary filter flask in a vacuum filtration.  Its purpose is to capture any excess liquid that might overflow out of the primary filter flask. 

Filtered off: (verb) A phrase that refers to the separation of a solid substance from a liquid.  Example: tea leaves can be filtered off of tea by passing the mixture through a strainer.  In chemistry, filtering a mixture is always a technique for separating different substances.

Filtering: (verb) The act of using filtration techniques to separate a solid from a liquid.

Filtervac: (noun) A small black rubber ring that is placed between a vacuum filter flask and a Buchner funnel to create a tight vacuum seal when suction is applied to the vacuum filter flask. 

Filtrate:(noun) The liquid that has passed through a filter. Example: liquid coffee.

Filtration: (noun) The separation of a liquid from a solid by pouring the mixture through a membrane with small holes (pores). The membrane can be, for example: filter paper or a sintered glass crucible.  See "vacuum filtration" for more information. 

Flared: (adjective) To expand or open outward in shape.  Is used in chemistry to describe the base of a graduated cylinder. The flared base helps prevent it from tipping over.

Flowchart: (noun) A schematic representation of a sequence of events.

Fluted filter paper: (noun) Filter paper that has been folded in a special manner to increase the surface area that comes into contact with the solution being filtered.  Fluted filter paper is only used with a conical glass funnel. 

Formula weight: (noun) The sum of the atomic weights of the atoms in a formula; is given units of grams/mol.

Fumehood: (noun) A special laboratory chamber fitted with a protective glass shield and containing a powerful extraction fan to remove toxic fumes.  The explosion-proof glass shield should always be pulled down low so that there is only enough room to slip your hands into the fumehood, thus protecting your face and body should an explosion occur. 

DG: (noun) Change in Gibbs free energy.  The thermodynamic function that takes into account both the enthalpy, H, and entropy, S, of a system; G = H ö TS.  For a reaction at constant temperature and pressure, DG = DH - TDS.  For a voltaic cell, DG is a measure of the maximum work that can be obtained from the cell.

Galvanic cell: (noun) A device in which chemical energy from a spontaneous redox reaction is changed into electrical energy that can be used to perform work.

Gas constant: (noun) The constant of proportionality (R) in the equation PV=nRT (the Ideal Gas Law).  R has the values of 8.31441 J/(mol · K) and 0.082057 (L · atm)/(mol · K).

Glass crucible: see "sintered glass crucible".

Glass funnel: see "Conical funnel".

Graduated cylinder: (noun) A thick-walled glass tube used for measuring out volumes of liquid.  The tube has an internal diameter of 1 to 3 cm, is closed at one end, and has a millilitre volume scale painted on the side.  Graduated cylinders are typically manufactured with maximum volumes of 10, 25, 50, or 100 mL. 

Gravity filtration: (noun) A filtration technique where the weight of the liquid mixture being filtered is the only force that acts on the mixture to make it pass through the filter.  Compare this to vacuum filtration.  Gravity filtrations usually involve the use of filter paper and a conical glass funnel. 

Gravimetric analysis: (noun) A certain type of quantitative analysis that allows one to calculate the exact percentage composition of a particular substance within a mixture of substances.  This method involves determining the exact mass of both the mixture and the particular substance of interest within the mixture.  Example: using gravimetric analysis, 2 grams of uranium are found in 50 grams of crushed rock, hence the sample is 4% uranium by weight.  The steps involved in gravimetric analysis are: dissolving the mixture, precipitating out the desired substance to be analyzed, filtering the mixture to separate out the precipitate, drying the precipitate, and weighing the precipitate.

Gravimetric technique: see "gravimetric analysis".

Half-cell: (noun) Half of a galvanic cell in which either an oxidation or a reduction occurs.

Half-equivalence point: (noun) The point on a titration curve where the volume is exactly one-half of that found at the equivalence point.  The pH at the half-equivalence pointis equal to the pK_a of the acid being titrated.

Half-reaction: (noun) Half of an oxidation-reductionreaction; an oxidation or a reduction.  See "oxidation half-reaction" and "reduction half-reaction".

Head pressure: (noun) The amount of force (pressure) that a droplet of liquid experiences as it comes out of the tip of a buret.  The pressure depends on the height of the liquid column within the buret.  The higher the liquid level, the greater the pressure, and hence the greater the volume of one drop of liquid coming out of the buret.  When a 50 mL buret is full, one droplet is ~ 0.08 mL, whereas one droplet is only ~ 0.05 mL when the same buret is only half-full.

Henderson ö Hasselbalch equation: pH = pKa + log ([conjugate base]/[conjugate acid])  This equation gives the relationship between the pH of an acid-base system and the concentrations (in units of M or moles) of base and acid.

Heterogeneous: (adjective) Consisting of dissimilar elements or parts; not homogeneous.

Homogeneous: (adjective)  Uniform in structure or composition throughout.  Opposite of heterogeneous.

Hotplate: (noun) A portable electric appliance with a flat ceramic top used for heating. 

Hydrated: (adjective) Contains water.  A solid compound in crystalline form that contains water molecules is called a "hydrate".

Hydrolysis: (noun) A reaction of a cation or anion with water that affects the pH of the solution.

Hygroscopic: (adjective) A substance that is readily absorbing moisture from the atmosphere is said to be hygroscopic.  This phenomenon explains why some ultra-dry solids are seen to gain mass when placed on an analytical balance.

Hypothesis: (noun) One or more assumptions put forth to explain the observed behavior of nature.  A large amount of experimental evidence can support a hypothesis, but a hypothesis can never be proven 100%.  It can, however, be disproved.  Example: Newtonian Mechanics was once believed to accurately describe all of the observed behaviour of moving objects.  However, four centuries later, the two theories of Relativity and Quantum Mechanics have shown that Newtonâs hypotheses about nature do not accurately describe it 100% of the time.  Newtonâs hypothesis has thus been disproved when objects are either moving near the speed of light, or the objects are on the atomic scale of size.

Ice bath: (noun) A mixture of crushed ice and cold water used to cool objects. 

Immiscible: (adjective) Something that will not mix with another substance is said to be immiscible.  Examples: oil and water; CH₂Cl₂ and water.

In situ: (adverb/adjective) Latin for "in the original position".  In chemistry, if a chemical is produced in situ, then it usually means that the chemical was formed in a reaction, and then immediately consumed by another chemical within the reaction mixture. Example: A + B + C ® D + B ® E.   In this case, "D" was produced in situ and immediately reacted with "B" to form "E".

Indicator: (noun) A chemical or mixture of chemicals used to test the acidity or basicity of a substance.  An indicator changes colour depending on the acidity of the solution being tested.  Many indicators are complicated organic substances. Some indicators used in the laboratory include litmus, phenolphthalein, methyl orange and bromothymol.  An indicator is required to visually show the endpoint of a titration. 

Insoluble: (adjective) Will not dissolve.  When one substance (X) will not dissolve in another substance (Y), then substance X is said to be insoluble in substance Y.  Example: NaCl is insoluble in acetone.

Iodometric titration: (noun) A special type of redox titration in which iodide (I^-) and soluble starch are used as the indicator.  As the titration approaches the equivalence point, excess iodine (I₂) is generated which immediately reacts with the starch to form an intensely bluish-purple coloured complex.  The appearance of this colour is taken to be the endpoint of an iodometric titration.

Ionic: (adjective) Pertaining to the state of being an ion.  Example: ionic lead is Pb²⁺.

Ionic solution: (noun) Any solution that contains dissolved ions. Can usually conduct electricity.

K_a: (noun) The acid dissociation constant.  For the reaction: HA(aq) + H₂O(l)  H₃O⁺(aq) + A^-(aq) [where HA is an acid and A^- is the conjugate base], the equilibrium expression would be: K_a = ([H₃O⁺][A^-])/[HA].  Note that all pure liquid terms are omitted, hence H₂O does not appear in the denominator.  Strong acids have much larger K_a values than do weak acids.

K_b: (noun) The base dissociation constant.  For the reaction: B(aq) + H₂O(l)  BH⁺(aq) + OH^-(aq) [where B is a base and BH⁺ is the conjugate acid], the equilibrium expression would be: K_b = ([BH⁺][OH^-])/[B].  Note that all pure liquid terms are omitted, hence H₂O does not appear in the denominator. Strong baseshave much larger K_a values than do weak bases.

K_sp: (noun) The "solubility product".  The constant for the equilibrium expression representing the dissolving of an ionic solid in water.  If K_sp > 1, the products on the right-hand-side of the chemical equation are favoured; if K_sp < 1, the reactants on the left-hand-side are favoured; and if K_sp = 1, then neither reactants or products are favoured.  K_sp can never have a value of "0".  The magnitude of K_sp signifies the extent to which either the products or the reactants are favoured.

K_w: (noun) The ion-product constant.  For the reaction: 2H₂O(l)  H₃O⁺(aq) + OH^-(aq), the equilibrium expression would be: K_w = [H₃O⁺][OH^-].  Note that all pure liquid terms are omitted, hence H₂O does not appear in the denominator. At 25° C, K_w = 1.0 x 10 ^ö14 = (K_a)(K_b).

L-ascorbic acid: (noun) The biologically active form of Vitamin C (C₆H₈O₆).  The "R" form is not biologically active.

LED: see "Light-emitting diode".

Level of accuracy: This phrase is used to qualitatively indicate the number of significant figures to which a value is known.  Examples: a top-loading balance or a graduated cylinder yields data with only 1 or 2 significant figures, hence only a low level of accuracy can be achieved using these devices.  An analytical balance or a pipet yields data with at least 4 significant figures, hence a high level of accuracy can be achieved using these devices.

Light-emitting diode: (noun) Abbreviated as "LED".  This electronic devices has many uses.  In our chemistry labs, diodes are the source of monochromatic light used in a colorimeter when performing colorimetric analysis.

Litmus paper: (noun) An indicator which turns red in the presence of acids and blue in the presence of bases.  The paper is manufactured by impregnating it with a water-soluble blue powder derived from certain lichens.  To help remember which colour indicates which pH, remember that "red" partially rhymes with "acid", while "blue" partially rhymes with "alkaloooo" (taken from alkali, which as another word for "basic"). 

Magnetic stir-bar: (noun) A small magnet, roughly the shape and size of a large pharmaceutical drug capsule.  The magnetic is coated in Teflon, so that it will not chemically react with whatever liquid that it is placed in.  The stir-bar spins under the influence of a magnetic stirrer.

Magnetic stirrer: (noun) An electrical device (that looks like small hotplate) that is used to stir solutions.  A flask of liquid is seated on top of the stirrer, a magnetic stir bar is placed inside the liquid, and the device is then turned on to whatever stirring speed is desired.  A rotating magnetic field generated by the magnetic stirrer spins the stir-bar inside of the solution. 

Melting point: (noun) The temperature at which a solid changes to a liquid.  The opposite process is the "freezing point".

Melting point analysis: (noun) The act of determining the melting point of a solid substance by slowly heating up a sample in a melting point apparatus and observing both the temperature at which the sample begins to melt, and the temperature at which all of the sample has melted.  The resulting values give the melting point range, and the smaller the range, the higher the purity of the sample. 

Melting point apparatus: (noun) An electrical device equipped with a thermometer, a magnifying glass, and heating block within which a hole has been drilled to allow a melting point capillary tube to be inserted.  Such devices can typically heat a sample to at least 500° C. 

Melting point capillary tube: (noun) A capillary pipet that has been sealed closed at one end, and is used to hold the solid sample that is being analyzed by melting point analysis.

Meniscus: (noun) The curved surface of a liquid that forms in a buret, pipet, or capillary tube.  The meniscus is convex (bulges upwards) for mercury and is concave (sags downwards) for water. 

Metal spatula: (noun) A small metal implement having a broad, flat, flexible blade that is used to mix, spread, or lift material. 

mg: (noun) "milligram".  This is 0.001 grams.

Millimoles: (noun) A unit equal to 0.001 moles.

Miscible: (adjective) Something that will mix homogeneously with another substance is said to be miscible.  Example: methanol and water.

Mol: see "Mole".

Molar: (adjective) Relating to a solution that contains X moles of solute per liter of solution, where X is a number.  Example: "a six molar solution of HCl" simply means 6 M HCl(aq).

Molar absorptivity coefficient: (noun) A characteristic value that is unique for every single known chemical.  It must be determined experimentally in the liquid (or dissolved) phase of a chemical using a colorimeter, and has units of L cm^-1 mol^-1.  It is abbreviated as e and used in Beerâs Law and colorimetric analysis.

Molarity: (noun) Given the symbol "M"; stands for the concentration of a solution.  The units are moles per liter.

Mole: (noun) Abbreviated as "mol".  The amount of substance that contains the same number of elementary entities as there are atoms in exactly 12 grams of C, which is 6.02205 x 10²³; hence Avogadroâs number is 6.02205 x 10²³ / mol.

The mole is the most important concept when it comes to laboratory chemistry concepts as it is used in almost all calculations.  See the Section on "Mole" in the Primer.

Monochromatic light: (adjective) Light composed of just one wavelength (colour).

Monoprotic acid: (noun) An acid that can lose only one proton (H⁺) per molecule (eg, HCl).

Mortar: (noun) A vessel made of stone in which substances are crushed or ground with a pestle. 

Nernst equation: (noun) An equation relating the potential of an electrochemical cell to the concentrations of the electrolytes in the cell.  E_cell = E°_cell ö (0.05991/n)log Q; where n = the number of electrons being exchanged per mole, and Q = the reaction quotient.

Neutralized: (adjective) A term used to describe the situation where either: (a) the number of moles of acid present in a solution equals the number of moles of base, and hence the pH is 7, or (b) when charge neutrality exists between a mixture of anions and cations.

Opalescent: (adjective) A descriptive word.  Something that looks like milk is opalescent.

Overshot: (adverb) The condition that is said to exist in a titration when enough titrant has been added to accidentally go beyond the equivalence point (or the endpoint).  This is one of the most common sources of error in a titration.

Oxidation: (verb) A reaction in which an atom, ion, or molecule loses electrons to an oxidizing agent. (The opposite of oxidation is reduction)  Example: Cu⁰ + Zn²⁺ ® Cu²⁺ + Zn⁰; here Cu⁰ is being oxidized by the oxidizing agent Zn²⁺.

Oxidation half-reaction: (noun) The part of an oxidation-reduction reaction that involves oxidation.  Usually involves a chemical equation.  Example: metallic aluminum foil placed in a beaker of warm, salty, water will clean dirty silver jewelry by reducing the black AgS back to pure Ag(0), as shown in the redox equation below:

AgS + Al(0) ® Ag(0) + AlS (redox reaction)

AgS + 2e^-® Ag(0) + S^2- (reduction half-reaction)

Al(0) ® Al²⁺ + 2e^- (oxidation half-reaction)

Oxidation-reduction: (noun) Any chemical reaction in which the transfer of electrons from one substance to another substance occurs.  The substance losing electrons is oxidized and the substance gaining the electrons is reduced.  Sometimes called "redox".

Oxide coating: (noun) A layer that forms on the surface of a substance when it reacts with atmospheric oxygen.  This oxide layer prevents any more oxygen from reacting with layers that are deeper within the substance.  Example: lithium will form a layer of Li₂O on its surface, but underneath that surface lies pure lithium.

Oxidized: (adjective) A chemical that has experienced oxidation.  Example: rust is oxidized iron.

Oxidizer: see "Oxidizing agent".

Oxidizes: (verb) The act of an oxidizing agent upon the chemical being oxidized.  Example: atmospheric oxygen oxidizes elemental iron, converting it to rust.

Oxidizing agent: (noun) A substance that takes electrons from another substance being oxidized (and therefore itself being reduced) in a redox reaction.Example: Cu⁰ + Zn²⁺® Cu²⁺ + Zn⁰; here Zn²⁺ is the oxidizing agent that becomes reduced to Zn⁰, while Cu⁰ is being oxidized to Cu²⁺.

Parallax error: (noun) The apparent displacement of an object as seen from two different points that are not on a line with the object.  For example, when viewing the meniscus of a liquid within a buret, the eye must be at the exact same level as the meniscus so that the volume scale can be read correctly.  If the eye is below the level of the meniscus, parallax error will cause the volume reading to be to small, whereas the reading will be too large of the eye is above the level of the meniscus. Caution must be taken to eliminate parallax error especially when preparing a standard solution in a volumetric flask. 

Pasteur pipet: (noun) A glass eye-dropper. 

Pestle: (noun) A club-shaped, hand-held tool made of stone used for grinding or mashing substances in a mortar. 

pH: (noun) A measure of the concentration of H⁺ions in a liquid. Neutral is pH 7.0; numbers greater than this are basic; smaller numbers are acidic. pH = -log[H⁺].

pH meter and probe: (noun) A device that accurately measures the pH of a solution.  A pH meter is a voltmeter that measures the electric potential difference between two electrodes when they are submerged in a solution.  The two electrodes are contained within a single slender rod called a "probe".  The readings are shown on a dial or digital display. The probe must never be left outside of either itâs storage solution, or the solution being measured because the special chemicals contained within the probe will dry out, destroying the probe.

Phase: (noun) A particular state of matter.  A substance may exist as a solid, liquid or gas, and may change between these phases with addition or removal of energy.  Examples: ice, liquid, and vapour are the three phases of water.  A fourth state of matter, called "plasma", is composed of an electrically neutral, highly ionized gas composed of ions, electrons, and neutral particles.  Plasma is distinctly different from solids, liquids, and normal gases.

Phase change: (noun) The event that occurs when a sufficient amount of energy is either added or removed from a phase to convert it into another phase. Example: ice undergoes a phase change to water when heat energy is added.

Phase separation: (noun) Any action that arranges a mixture of a liquid and a solid such that the two phases are no longer mixed together. Example: An aqueous solution containing a PbSO₄ precipitate will experience phase separation as the precipitate settles to the bottom of the beaker. 

Phenolphthalein: (noun) An acid-base indicator that is pink when in basic media and colourless in acidic media. 

Photogate: (noun) An electronic device having a detector and a photon transmitter (such as a light bulb).  The detector measures any change in the intensity of the light as an object passes between the transmitter and the detector.  Such devices are commonly used to automatically open doors as a person approaches them.  In the chemistry lab, it is used to count the number of drops that come out of a buret, thus allowing a computer to automatically construct a titration curve during a pH titration experiment.  The device is also called an "electric eye".

Pipet bulb: (noun) A large rubber suction bulb (the size of a small lemon) used to suck liquid up into a pipet. 

Pipet: (1) (noun) A piece of volumetric glassware use to measure out an exact amount of liquid.  Pipets come in many sizes, but the frequently encountered pipets dispense either 10.00 mL or 25.00 mL of liquid. (2) (verb) The act of using a pipet to transfer a solution from one flask to another flask.

Pipette: see "pipet".

pK_a: (noun) The negative logarithm (base 10) of an acid dissociation constant; pK_a = - log K_a. This value is used in the Henderson ö Hasselbalch equation.

Plate out: (verb) This phrase is used to describe the physical accumulation of solid metal on the cathode of an electrochemical cell.  Example: An anode made of gold (Au) releases Au⁺ into the electrolytic solution as current flows across to the cathode, resulting in deposition of solid gold onto the cathode.  This process is used to electroplate metallic objects, such as a spoon, with a surface layer of silver or gold and is called either "silver-plating" or "gold-plating".

Point of inflection: (noun) The point on a curved line where the shape changes from concave to convex.  The letter "S" contains a point of inflection at the very centre of the shape of the letter.  On a titration curve, the equivalence point is located at the point of inflection of the curve. 

Pole: (noun) Either of two oppositely charged terminals (electrodes) in an electrochemical cell.  Example: the + and - ends of a AA battery.

Polychromatic light: (adjective) Light composed of many wavelengths (colours).

Polypropylene: (noun) A polymer (plastic) made of C and H atoms and used in the manufacturing of thousands of different items.  Most weigh boats and wash bottles found in a chemistry laboratory are made of this material.

Porosity: (noun) A measure of the size of the holes (pores) present in a membrane, such as filter paper or a sintered glass crucible.  A membrane with high porosity has larger holes than one with low porosity, and as such will allow a liquid to be filtered through it much quicker, but might not be able to trap smaller particles.  Example: using a paper filter (low porosity) when making coffee takes longer than using a metal filter (medium porosity), but will result in liquid coffee free of coffee grounds, unlike the coffee obtained with a metal filter. Sintered glass crucibles are ranked as course (C), medium (M), fine (F), and very fine (VF) with the pore diameters being 40-60 mm, 10-15 mm, 4-5.5 mm, and 2-2.5 mm, respectively.

Potential: see "Voltage".

Potentiometric titration: (noun) A titration method that involves measuring changes in the voltage of an electrode immersed in the solution that is being titrated.  The most common example of this is an acid-base titration where the pH of a solution is measured using a pH meter and a pH probe, so as to generate a titration curve.

Precipitate: (noun) Abbreviated as "ppt".  A solid substance that forms as a result of a chemical reaction that is taking place in a liquid medium (usually water).  Filtration of the mixture allows the precipitate to be separated from the liquid.

Precipitated: (adverb) A substance that has already formed a precipitate in a solution is said to have been precipitated.  Sometimes the phrase "precipitate out of solution" is also used.

Precipitating agent: (noun) A chemical substance that will cause another substance to form a precipitate.  Example: when HCl is added to AgNO₃ that is dissolved in water, a white precipitate of AgCl forms; HCl is the precipitating agent.

Precipitating reagent: see "Precipitating agent".

Precipitating: (verb) A substance that is currently becoming insoluble during a chemical reaction that is taking place in a liquid.

Precipitation:(verb) The formation of an insoluble substance (called a precipitate) during a chemical reaction that is taking place in a liquid. For example: a solid white powder of AgCl will form when HCl is added to it.

Primary filter flask: (noun) The filter flask used in a vacuum filtrationto capture the filtered liquid.  Any excess liquid that overflows out of this flask is caught by the filter trap. 

Primary standard: see "standard".

Product: (noun) A substance formed in a chemical reaction.  It appears to the right of the arrow in a chemical equation.

Purification: (noun) The process of removing all impurities from a mixture, perhaps by precipitation or filtration.

Q: see "reaction quotient".

Qualitative analysis: (noun) Any analysis that involves determination of the identity of substances present in a sample with no regard to the quantity of the substances.  Such analyses could be as simple as determining with your taste buds whether you are drinking Coke, Diet Coke, or Caffeine-Free Diet Coke, as in each sample you are identifying different flavour-releasing substances.  Hospitals and police crime labs are constantly using qualitative analysis to determine which drugs are present in a blood sample.  From a chemistry standpoint, qualitative analysis usually involves the separation and identification of individual ions in a mixture.  Once the identity of the substances is known, quantitative analysis can then be performed to determine the amounts of the substances present.

Qualitatively: (adverb) Determining a relative property of a substance, without assigning numerical values.  Example: the word "hot" merely indicates that the temperature is likely to be greater than room temperature.

Quantitative accuracy: (noun) The careful measurement of a property that allows for a considerable number of significant figures to be reported with a high degree of certainty.  Example: the use of a pipet to transfer 25.00 mL of liquid ensures that the volume quantity will be know to 4 significant figures of accuracy.

Quantitative analysis: (noun) Any analysis that involves determining exact amounts.  Taking a look at your bank account is an exercise in quantitative analysis.  From a chemistry standpoint, quantitative analysis involves determining how much of an element or molecule is in a sample.  Applications are far reaching, and include measuring levels of toxic contaminants in the environment, to the purity of the gallium arsenide used in semiconductor chips.  A vast number of techniques and instruments have been invented for the sole purpose of conducting quantitative analyses.

Quantitatively transfer: (adverb) The act of transferring a solid or liquid substance from one container to another without losing any of the material.  This allows one to maintain a high level of accuracy in oneâs data.  Example: pouring 10 mL of 2 M NaOH(aq) from a 50 mL beaker into a 250 mL beaker, and then thoroughly rinsing out the 50 mL beaker with distilled water and pouring the rinsings into the 250 mL beaker will guarantee that every single molecule of NaOH (all 0.02 moles worth) is transferred into the 250 mL beaker.  The entire quantity has thus been transferred. 

Rate: (noun) A quantity measured with respect to another measured quantity.  Example: the methane was converted to methanol at a rate of 0.01 moles per second.

Reaction: (noun) The recombination of two substances using parts of each substance to produce new substances. Example: HCl(aq) + NaOH(aq) ® NaCl(aq) + H₂O(l).

Reaction quotient: (noun) Abbreviated as "Q".  The ratio of the initial concentrations of products to reactants present in a reaction before equilibrium is established.  This differs from "K" which is the ratio of the concentrations of products to reactants in a reaction once equilibrium has been established.  If Q = K, then the reaction is at equilibrium, if Q < K, the reaction will favour the products and proceed to the right, and if  Q > K, the reaction will favour the reactants and proceed to the left.

Reactant: (noun) A substance consumed in a chemical reaction.  It appears to the left of the arrow in a chemical equation.

Reagent: (noun) A commonly available substance (reactant) used to create a reaction.  Reagents are the chemicals normally kept on chemistry laboratory benches.  Many substances called reagents are most commonly used for chemical testing purposes.

Redox titration: (noun) A titration where one of the components is an oxidizing agent and the other is a reducing agent.

Redox: (noun) A reaction that involves oxidation and reduction; a reaction in which electrons are transferred from one substance to another.

Reduce the volume: (verb) To make the liquid quantity of a particular substance smaller.  This usually involves boiling off a portion of the liquid, so as not to lose whatever chemical might be dissolved within the liquid.

Reduced: (1) (adjective) A chemical that has experienced reduction.  (2) (adjective) A substance that has had one of its properties made smaller.  Example: The liquid volume of the Cola was reduced in half by boiling off 50 mL of Cola.

Reducing agent: (noun) A substance that gives electrons to another substance being reduced (and therefore itself being oxidized) in a redox reaction. Example: Cu⁰ + Zn²⁺® Cu²⁺ + Zn⁰; here Cu⁰ is the reducing agent that becomes oxidized to Cu²⁺, while Zn²⁺ is being reduced to Zn⁰.

Reduction half-reaction: (noun) The part of an oxidation-reduction reaction that involves reduction.  See "oxidation half-reaction" for an example.

Reduction: (verb) A reaction in which an atom, ion, or molecule gains electrons from a reducing agent.  (The opposite of reduction is oxidation.)  Example: Cu⁰ + Zn²⁺ ® Cu²⁺ + Zn⁰; here Zn²⁺ is being reduced by the reducing agent Cu⁰.

Remain in solution: (adverb) This phrase means that a dissolved ion does not precipitate when another chemical is added to the solution.

Reproducibility: (noun) The quality of being able to repeat an experiment that involves making a measurement, and get practically the same answer each time.  Any scientific study that is conducted with a high degree of reproducibility is considered to have produced reliable data.

Residue: (noun) Matter remaining after completion of an extraction procedure.  Example: the stains on the bottom of a coffee mug are a residue of the various chemical components of coffee left behind after the water component has evaporated.  In this example, the water is the component that has been extracted via evaporation.

Ring Stand: (noun) A cast-iron block of metal, (about the size of a CD jewel-case) with a stainless-steel rod (about 1 cm thick and 2 feet long) rising vertically from it at a perpendicular angle.  Various clamps can be attached to the rod to hold such items as thermometers, Erlenmeyer flasks, separatory funnels, etc. 

R_f: (noun) Abbreviation for "rate of flow".  A measure of the distance that a compound moved on a chromatographic plate under the influence of the carrier phase, divided by the distance that the carrier phase itself moved.  This number can be used to compare the results obtained to other chromatographyexperiments, even if the carrier phase is allowed to rise to different heights in each experiment.

For example, a mixture of substances X and Y is placed as a small spot at the bottom of a chromatographic plate.  The mixture is then eluted with ethanol for 5 minutes, after which time the plate is removed from the chromatographic chamber. Using a ruler, one finds that the ethanol climbed 4.5 cm up the plate, while a spot is seen at 4.1 cm, and another is seen at 2.6 cm.  The R_f values for the two spots are 0.91 (from 4.1/4.5) and 0.58 (from 2.6/4.5).  Which spot corresponds to which compound?

If one places a spot of pure X on a plate and elutes it, one might find that the ethanol climbed 3.4 cm, while the spot of pure X climbed 2.0 cm.  The R_f value for pure X is thus 0.59. Similarly, an experiment conducted with pure Y might show that the ethanol moved 6.6 cm while the spot of pure Y climbed 6.0 cm.  The R_f value for pure Y is thus 0.91.

Based on these two experiments, it can now be determined that the spot seen at 4.1 cm in the first chromatography plate (containing the mix of X and Y) must correspond to substance Y, while the spot seen at 2.6 cm must correspond to substance X. 

Room Temperature: (noun) Abbreviated as "room temp".  This is chemistry lab jargon that stands for 20° C, unless otherwise stated.

Rubber policeman: (noun) A glass stirring rod with a small rubber scraper attached to one end.  Used to scrape solid materials out of a beaker. 

Salt: (noun) A compound derived from the reaction of an acid and a base; it contains a cation from the base and an anion from the acid.  Example: NaCl contains Na⁺ from the base NaOH and Cl^- from the acid HCl.

Salt bridge: (noun) Either a tube filled with a concentrated solution of an electrolyte, or a permeable material (eg, paper towel, candle wick) soaked in a concentrated solution of an electrolyte. The salt bridge is used to connect two half-cells of an electrochemical cell and conduct electricity between them while preventing their contents from mixing.

Saturated: (adjective) A state in which a liquid can hold no more of a substance.  If any more of the substance is added, it will not dissolve.  See "Saturated solution".

Saturated Solution: (noun) A solution that holds the maximum possible amount of dissolved material.  When saturated, the rates of solid dissolving and solid recrystallizing are the same, and a condition of equilibrium is reached.  The amount of material in solution varies with the temperature; cold solutions can hold less dissolved solid material than hot solutions.  Gases are more soluble in cold liquids than in hot liquids.

Semimicro: (adjective) Any laboratory technique that is carried out on a fairly small scale.  Example: performing a chemical reaction using 2 mL of chemicals in a test tube would be considered a semimicro reaction, whereas using 50 mL in a beaker would not.

Separatory funnel: (noun) A pear-shaped, glassware funnel designed to permit the separation of immiscible liquids by simply pouring off the more dense liquid while leaving the less dense liquid in the funnel. 

Significant figures: (noun) Digits in a measurement that indicate the precision of the measurement.  These figures include all those that are known with certainty plus one more, which is an uncertain estimate.  Example: "0.4346" has four "sig figs"; with the 434 known and the 6 an estimate.  The number 4.346 x 10^-1 also has four sig figs.  The number "0.0078" has only two sig figs, whereas "0.007800" has four sig figs; these would be written as 7.8 x 10^-3 and 7.800 x 10^-3, respectively. "1.0078" has five sig figs, while "10.0078" has six sig figs.

Sintered: (verb) To cause a powder to form a coherent mass by heating it without melting it.

Sintered glass crucible: (noun) A special funnel that is used for filtering solid matter out of a solution.  Half-way down the funnel is a flat disk of glass with millions of microscopic holes (pores) in it.  The liquid passes through the disk, but any solid matter is trapped on the glass disk.  This disk is made of glass that has been sintered.  It is called a crucible because it can be heated in an oven to high temperatures so that the solid matter trapped on the filter can be dried.  A chemist uses a sintered glass crucible, and not filter paper, whenever the solid matter must be dried in an oven, as filter paper will burn in an oven. 

Sintered glass filter: see "sintered glass crucible".

Soluble: (adjective) When one substance (X) will dissolve in another substance (Y), then substance X is said to be soluble in substance Y.  Example: NaCl is soluble in water.

Solubility behaviour: (adjective) The manner in which a substance reacts in the presence of other chemicals determines its solubility behaviour.  The substance might be soluble in a particular liquid and be insoluble in another liquid.  Similarly, the addition of a chemical to a dissolved substance may, or may not, cause the substance to form a precipitate.  All these various responses to different chemicals make up a substanceâs solubility behaviour.

Solute:(noun) The minor substance or substances present in a solution.  Example: ethanol is a solute of wine because it only constitutes 11 to 14% of the total volume; water is the solvent.

Solution: (noun) A liquid mixture of two or more pure substances that is uniform throughout (homogeneous).  The substance present in the greatest quantity is the solvent while the other less abundant substances are all solutes.

Solvate: (verb) To cause the solvationof a substance.

Solvation: (noun) Any of a class of chemical reactions in which solute and solvent molecules combine with relatively weak covalent bonds.  Example: CuCl becomes CuCl · 2H₂O when it is exposed to water.

Solvent: (noun) The major substance present in a solution.  Any liquid can potentially become a solvent once it is mixed with another substance.  Example: water is the solvent in wine, because the ethanol portion is only 11 to 14% of the total volume.

Spatula: see "Metal spatula".

Spectator ion: (noun) An ion that is present during the course of an aqueousreaction but one that does not take part in the reaction.  Example: in the reaction of KI with KIO₃ in acidic water (shown below) the K⁺ ions are spectator ions:

KIO₃(aq) + 5KI(aq) + 6H⁺(aq) ® 3I₂(l) + 6K⁺(aq) + H₂O(l).

Spectrum: (noun) The distribution of energy emitted by a radiant source.  The pattern of electromagnetic radiation can be plotted as wavelength vs. intensity (as is seen in an absorption spectrum in colorimetric analysis).  There are many different types of spectrums that scientists measure, each depending on what the radiation is (radiowave, microwave, gamma-ray, X-ray, ultraviolet light, visible light etc).

Spotted: (adjective) This term applies to thin-layer-chromatography.  When the mixture to be separated is first dissolved in a suitable solvent, and then a tiny amount (microliters) of this liquid is placed onto a chromatographic plate using a capillary pipet, the sample is said to have been "spotted" onto the plate. 

Standard: (noun) A substance whose concentration is already known to a high degree of accuracy.  It can be used as a benchmark reference by which other substances can be compared. If the standard substance is a solid compound, it is 100% pure.

Standard cell potential: (noun) Given the symbol "E°_cell".  A half-cell potential for a chemical reduction that is used as a reference for other reductions.  Note that all standard cell potentials are ultimately referenced to the reduction of hydrogen (2H⁺ + 2e^- ® H₂), which is assigned a value of 0.0 V.  For example: an electrode gives a reading of ö0.6 V for the reduction of hydrogen, and a reading of ö3.4 V for the reduction of zinc. The values are corrected so that the reduction of hydrogen is 0.0 V and that of zinc is ö2.8 V.  Also called a "standard electrode potential".

Standard conditions: (noun) An experiment conducted at room temperature and regular atmospheric pressure.

Standard electrode potential: (noun) Given the symbol "E°".  See "Standard cell potential".

Standard emf: (noun) The emf of an electrochemical cell in which all reactants and products are present in their standard states.

Standard hydrogen electrode: (noun) A special electrode that measures the reduction of hydrogen and whose readings are taken as the reference with which readings obtained from all other types of electrodes should be compared.  This electrode consists of a platinum metal electrode immersed in an acidic solution where the [H⁺] = 1.0 M, and with 1 atm of H₂ gas bubbling over the surface of the electrode. The reaction 2H⁺ + 2e^-® H₂ is given the value of 0.0 V.

Standard reduction potential: (noun) The potential of a half-reaction under standard state conditions, as measured against the potential of a standard hydrogen electrode.

Standard solution: (noun) A liquid solution whose concentration is already known to a high degree of accuracy; it is sometimes also called a "primary standard solution".  A standard solution can be used to accurately determine the concentration of another solution via titration.  This process is called standardization. 

Standardization: (verb) The act of using a standard solution and titration techniques to accurately determine the concentration of another solution.

Standardize: (verb) The act of determining the concentration of a liquid substance to a high degree of accuracy by titrating it with a standard solution.

Standardized: (adjective) A liquid substance whose concentration has been determined to a high degree of accuracy by titrating it with a primary standard solution.

Standard state: (noun) A reference state for a specific substance defined according to a set of conventional parameters.  For a gas, the standard state is 1 atm pressure; for a dissolved ion, the standard state is 1 M, and for a liquid or a solid, the standard state is the pure liquid or solid form of the substance.

Stationary phase: (noun) The substance in a chromatography experiment on which the chemical mixture is being separated (eluted).  Examples: In paper chromatography, the paper is the stationary phase.  It is dipped into a solvent (the carrier phase).  In column chromatography, the stationary phase is usually silica gel.  The solvent is poured on top of the column of silica gel.

Stirring rod: (noun) A rod, usually made of glass, but sometimes plastic, used to stir liquids.  The rod is typically as thick as a pencil and between 6 and 12 inches long. 

Stoichiometry: (noun) The quantitative relationships between the elements that make up a compound and between the elements and compounds that are involved in a chemical reaction.

Stopcock: (noun) A valve that regulates the flow of liquid through a pipet or a separatory funnel. 

Stopper: (noun) An object designed to fill a hole tightly.  Examples: a rubber bath plug, a cork stopper for a test tube, a glass plug for a volumetric flask. 

Strainer: (noun) A wire or plastic mesh/screen through which a liquid is passed to separate it from solid matter; the simplest type of filtration.  It can also be used to separate small solid particles from larger solid particles, such as sifting gravel to yield sand and pebbles. 

Strong acid: (noun) An acid that completely dissociates in an aqueous solution to produce an H⁺ ion and the conjugate base.  Example: HCl(aq) ® H⁺(aq) + Cl^-(aq).  Note that this is not an equilibrium.  Strong acids typically are capable of dissolving many substances.

Strong base: (noun) A base that completely dissociates in an aqueous solution to produce an OH^- ion and the conjugate acid.  Example: NaOH(s) + H₂O(l) ® Na⁺(aq) + OH^-(aq) + H₂O(l).  Note that this is not an equilibrium.  Strong bases typically are capable of dissolving many substances.

Sublimate: (1) (verb) To transform directly from the solid to the gaseous state without becoming a liquid.  Example: dry ice (solid CO₂) sublimates directly to CO₂ gas. (2) (noun) The purified solid substance collected during a sublimation is called the "sublimate".

Sublimation: (1) (noun) To sublimate.  (2) (noun) A separation technique used to purify a solid chemical substance.  The substance to be purified is placed into a vacuum filter flask that has been fitted with a cold finger, and then the flask is placed on an electric hotplate.  Next, the water pump is turned on to lower the pressure within the vacuum filter flask, and then the heat is turned on to sublime the substance within the flask.  The hot chemical vapours rise until they hit the cold finger, at which point the vapours condense onto the cold finger.  The condensed substance is called the sublimate and is a pure form of the substance that was sublimed.  Various other impurities initially present will either not sublime, and hence remain at the bottom of the filter flask, or they will not condense onto the cold finger and will be sucked out of the filter flask by the water pump.  This general method is called distillation when applied to a mixture of liquids. 

Subliming: (verb) The act of sublimation.

Supernatant: (adjective) The fluid above a sediment or precipitate.

Terminal: (noun) Either of the ends of the conducting circuit of an electrical apparatus.  In an electrochemical cell, the two electrodes are both terminals.  The + and ö ends of a battery.

Test tube: (noun) A clear, cylindrical glass tube open at one end and rounded at the other; used in laboratory experimentation. 

Test tube block: (noun) A piece of wood with 6 to 20 large holes drilled in it to hold test tubes. 

Test tube clamp: (noun) Similar to beaker tongs, but much smaller and designed to hold a test tube.

Theophylline: (noun) A colourless, crystalline, alkaloid found in tea leaves which can be used medicinally as a bronchial dilator. Formula is C₇H₈N₄O₂.

Thermal hydrolysis: (noun) A hydrolysisreaction that requires heat as a driving force.  In the case of the thermal hydrolysis of thioacetamide, the cation would be CH₃CS^(-)NH₂, and the pH rises due to the formation of NH₄⁺.  See "hydrolysis".

Thermistor: (noun) An electrical probe used for measuring temperature.  It is made of various semiconductor materials whose electrical resistance varies as a function of temperature. 

Thermometer: (noun) An instrument for measuring temperature.  It usually consists of a glass tube marked with a temperature scale, and a bulb containing a liquid (typically mercury or coloured alcohol) that expands and rises in the tube as the temperature increases. 

Thin-layer chromatography: (noun) A type of "chromatography".  Similar to paper chromatography, where paper is the stationary phase.

Titrant: (noun) The solution in a titration that is being added to another chemical.  The titrant is the solution that is in the buret, while the titrate is the solution that is in the Erlenmeyer flask.

Titrate: (1) (verb) The act of performing a titration.  (2) (noun) The solution in a titration that is having another chemical added to it.  The titrate is the solution in the Erlenmeyer flask, while the titrant is the solution that is in the buret.

Titrated against: (verb) A descriptive phrase.  Example: "solutionX is titrated against Y" means that X is titrated with Y (the standard solution)to determine the concentration of solution X.

Titration curve: (noun) A graph that shows how the pH of a solution changes during the course of a titration; the pH is plotted against the volume of the titrant; that is, the acid or base added. 

Titration: (noun) The analytical process where a standard solution is reacted with a solution of unknown concentration in order to determine the concentration of the unknown. 

Top-loading balance: (noun) An electronic scale that can measure the mass of an object to an accuracy of ± 0.1 grams. 

Transition metals: (noun) The forty elements in Groups 3-12 of the periodic table.  The four rows span Sc-Zn, Y-Cd, La-Hg, and Ac-Uub.

Tweezers: (noun) A holding tool consisting of a compound metal lever. 

Vacuum filtration: (noun) A filtration technique where suction is applied to the mixture of solid and liquid being filtered so as to pull the liquid through the filter.  This technique is much faster than gravity filtration.  Vacuum filtration usually involves the use of a vacuum filter flask, a filter trap, a water pump, and either a Buchner funnel or sintered glass crucible.  The liquid mixture is poured into the filter (Buchner or sintered glass), the liquid is sucked down into the filter flask by the action of the water pump, and any excess liquid that overflows out of the filter flask is caught in the filter trap.  The solid matter is left on the surface of the filter. 

Vacuum flask: see "Filter flask".

Vacuum sublimation: see "sublimation".

Vacuum sublimation apparatus: (noun) This consists of a vacuum filter flask, a cold finger, a hotplate, and a water pump. See "sublimation" for more information. 

Volatile: (adjective) The property of evaporating readily at or near room temperature (25° C).  Many organic liquids are said to be volatile because of their low boiling points and are highly combustible because of this property.  Example: diethyl ether (CH₃-O-CH₃) is considered to be very volatile as it boils at 35° C.

Voltaic cell: (noun) An electrochemical cell that uses a chemical reaction to produce electricity; also called a galvanic cell.

Voltage: (noun) electromotive force or potential difference, expressed in units of volts (V).

Voltmeter: (noun) An instrument for measuring potential differences in volts.

Volumetric analysis: (noun) A chemical analysis that is based on the measurement of the volume of a solution.  The prime example of this is a titration.  The term volumetric analysis is practically synonymous with titrations. 

Volumetric flask: (noun) A special glass vessel used for holding or measuring out a precise volume of liquid to a high level of accuracy.  The vessel has a pear-shaped body with a long, tall neck coming out of the top.  At a certain point on the neck is etched a calibration mark.  When the flask is filled with liquid such that the meniscus of the liquid is at the calibration mark, the volume of the liquid will be known to a high level of accuracy.  Volumetric flasks are manufactured in many volumes, including 10.00 mL, 25.00 mL, 100.00 mL, 250.00 mL, and 500.00 mL. A 250 mL beaker can only measure out liquid to ± 5 mL, but a 250.00 mL volumetric flask can measure out liquid to ± 0.12 mL. These flasks are always used in the preparation of standard solutions. 

Volumetric glassware: (noun) Glassware designed for use in volumetric analysis and as such can be used to obtain data with a high level of accuracy.  Examples include the pipet and volumetric flask. 

Volumetric pipette: see "pipet".

Volumetric techniques: (noun) This term includes all techniques required to perform a good titration, such as an understanding of significant figures, quantitative transfer, volumetric flasks, pipets, standard solutions, level of accuracy, and weighing by differences.  Not included would be any knowledge of the actual chemical reactions happening during a titration, or the use of an indicator.

Wash bottle: (noun) A plastic bottle with a spout coming out of the screw-cap top.  Squeezing the bottle will send a stream of liquid out of the spout.  These bottles are usually used for dispensing small amounts of distilled water. 

Wash: (verb) A separation technique.  The act of using a liquid chemical to remove a specific chemical out from a mixture of chemicals.  The mixture can contain either solid or liquid chemicals or both.  Example #1: pouring water over a mixture of PtCl₂ and NaCl crystals that are sitting on filter paper in a Buchner funnel will result in the NaCl crystals being dissolved and washed through the filter paper, while the PtCl₂ crystals (which are insoluble in water) will remain on the filter paper.  Example #2: pouring CH₂Cl₂ into Coca-Cola will result in the caffeine being "washed" into the immiscible CH₂Cl₂ layer as: (a) caffeine is more soluble in CH₂Cl₂ than in water, and (b) water and CH₂Cl₂ do not mix. 

Waste bottle: (noun) A container set up in the lab into which all waste material must be placed if the material is not allowed to be either poured down the sink or thrown into the regular trash can.  Any material which is environmentally unfriendly must go into a waste bottle.

Watch glass: (noun) A disk of thick curved glass, roughly 4 inches in diameter.  Used mostly for covering beakers when boiling water or to prevent dust from falling into the beaker. 

Water pump: (noun) A water tap with a small hose attached to the side of the pipe in such a manner that as water exits from the regular end of the tap, a suction force is created at the hose.  A water pump is used to provide the vacuum required for vacuum filtrations and vacuum sublimations. 

Water soluble: (adjective) Any substance that will partially or completely dissolve in water.

Weak acid: (noun) An acid that only partially dissociates in an aqueous solution to produce H⁺ ion and the conjugate base.  Example: CH₃COOH(aq) H⁺(aq) + CH₃COO^-(aq).  Note that this is an equilibrium.  Weak acids are not typically capable of dissolving as many substances as are strong acids.

Weak base: (noun) A base that reacts only partially in an aqueoussolution to produce an OH^- ion and the conjugate acid.  Example: NH₃(g) + H₂O(l)  NH₄⁺(aq) + OH^-(aq).  Note that this is an equilibrium.  Weak bases are not typically capable of dissolving as many substances as are strong bases.

Weigh boat: (noun) A small plastic dish (made of polypropylene), usually octagonal in shape, that is used for holding small amounts of solid substances while they are being weighed on a balance.

Weighed accurately: (adverb) This phrase means that a substance has been weighed on an analytical balance and thus its mass is known to a high level of accuracy.

Weighing by differences: (noun) This phrase describes the technique that is used to accurately weigh a sample of solid matter, in conjunction with a top-loading balance and then an analytical balance.  A weigh boat is placed on a top-loading balance which is then "zeroed" so that the mass of the weigh boat reads as 0.0 grams.  The sample is then weighed out into the weigh boat to the approximate desired mass (say, 1.2 grams).  The weigh boat and sample is then placed on the balance pan of an analytical balance and the combined mass of the weigh boat and the sample is recorded (say 1.5633 grams).  The solid matter is then dumped into a beaker, and the now empty weigh boat is weighed (say 0.3216 grams).  This latter number is subtracted from the first to yield the exact mass (say 1.2417 grams) of the material that was dumped into the beaker to a high level of accuracy.  This technique must be used as quite often a few grains of the solid material being weighed out sticks to the weigh boat. 

Weight percentage: (noun) The percent of a substance, by mass, that is present in a mixture.  Example: If 0.3 grams of iron are found in 10 grams of sand, the weight percentage of iron is 3%.

Wet: (adjective) Containing water.  A solid can be "wet" if it has been hydrated.  Example: the solid of NiCl₂ · 6H₂O is "wet" because it has six hydrated water molecules.  A liquid can be "wet" if it contains water.  Example: acetone with traces of water in it is "wet" while pure acetone is "dry".

Wire brush: (noun) A brush used to clean out test tubes.