Base – A base is a compound that produces OH– ions or electrons in water or that accepts protons. An example of a common base is sodium hydroxide, NaOH. A substance that will neutralise an acid is called a base. When an acid reacts with a base, a salt and water is formed. If a base is soluble in water, it is called an alkali.
Balanced chemical equation – If ever you write a chemical equation using symbols it MUST be balanced. That means that there must be the same number of each kind of atom on either side of the equation.
Barometer – a device used to measure the pressure in the atmosphere
Basalt – An igneous rock which cooled quickly from magma. The rapid cooling (perhaps under water) caused it to have small crystals.
Base anhydride – are not Arrhenius bases because they do not accept protons; they are not Brønsted–Lowry bases because they do not increase the hydroxide ion concentration of water. However, they are Lewis bases, because they will share an electron pair with some Lewis acids, most notably acidic oxides.
Beta particle – A beta particle is an electron, although the term is used when the electron is emitted in radioactive decay.
Beat – a slow oscillation in amplitude of a complex wave
Beer-Lambert law – Lambert’s law stated that absorbance of a material sample is directly proportional to its thickness (path length). Much later, August Beer discovered another attenuation relation in 1852. Beer’s law stated that absorbance is proportional to the concentrations of the attenuating species in the material sample in 1852.
Biochemistry – the chemistry of organisms
Biological weathering – Rocks can be broken down in many ways. Biological weathering is the breakdown of rocks by biological action. A good example is where the roots of plants growing in cracks in rocks causes them to split.
Binary compound – A binary compound is one made up of two elements.
Binding energy – Binding energy is the energy that holds protons and neutrons together in the atomic nucleus.
Boiling – the phase transition of liquid vaporizing. When boiling, a liquid is evaporating as fast as it can. If you look at a boiling liquid (careful!) you will see that it is forming bubbles in the body of the liquid.
Boiling point – the temperature in which the substance starts to boil. This is the maximum temperature a liquid can achieve. For water, the boiling point is 100oC (at standard atmospheric pressure). Pure liquids have a single steady boiling point.
Boiling point range – In the fractional distillation of crude oil, the substances are collected in groups (fractions) according to their boiling point range.
Boiling-point elevation – the process where the boiling point is elevated by adding a substance
Bonds – There are three main kinds of bonds at GCSE level. A Bond is the attraction and repulsion between atoms and molecules that is a cornerstone of chemistry.
An ionic bond holds two ions (of opposite charge) together by electrostatic attraction. Ionic bonding occurs between a metal and a non-metal. A good example is sodium chloride.
A covalent bond uses a shared pair of electrons to hold two atoms together. This usually occurs between two non-metal atoms. There are covalent bonds between the atoms in ammonia.
A metallic bond is formed by a delocalised sea of electrons surrounding the very tightly packed metal atoms.
Bond energy – Bond energy is the amount of energy required to break one mole of chemical bonds.
Bond length – Bond length is the average distance between the nuclei of two atoms that share a bond.
Boyle’s law – or the pressure-volume law states that the volume of a given amount of gas held at constant temperature varies inversely with the applied pressure .
Brine – A solution of sodium chloride (common salt) in water is called brine.
Buffer – A liquid that resists change in pH when an acid or base is added. A buffer consists of a weak acid and its conjugate base. An example of a buffer is acetic acid and sodium acetate.
Bubble – A bubble contains a gas. Bubbles in a liquid when it is boiling contain the vapour of that liquid. Bubbles of gas can be formed during a chemical reaction.
Brønsted-Lowrey acid – A chemical species that donates a proton
Brønsted-Lowrey base – A chemical species that accepts a proton
Buffered solution – An aqueous solution consisting of a weak acid and its conjugate base or a weak base and its conjugate acid that resists changes in pH when strong acids or bases are added
Burette – (also buret) – glassware used to dispense specific amounts of liquid when precision is necessary (e.g. titration and resource dependent reactions)
Calorimetry – Calorimetry is the study of heat flow. Calorimetry may be used to find the heat of reaction of two compounds or the heat of combustion of a compound, for example.
Calx – It was believed to be an ash-like substance which is left when the phlogiston leaves a metal. Although we now believe that metals form metal oxides when they burn, we no longer believe the phlogiston theory.
Carbon dioxide – This is a slightly acidic gas that is formed whn carbon burns in air (or oxygen). It does not support combustion and so a burning splint will be extinguished by the gas. However, this is NOT the test for carbon dioxide. To test for the gas, bubble it into limewater. A milky white precipitate shows that the gas is carbon dioxide.
Carbon dioxide is produced during respiration (this is true whether the respiration is by animals, plants or even anaerobic respiration of yeast during fermentation).
Carbon monoxide – This has the formula CO and is a possible product if a fuel burns in a poor supply of air. It is a toxic gas. It can be removed from the exhaust gases of cars by the use of a catalytic converter. You should be able to write a word equation for its formation during a combustion reaction.
Carbon steels – Steel can contain up to 1.5% of carbon. This is much less than the 4% found in cast iron.
Carboxylic acid – A carboxylic acid is an organic molecule containing a -COOH group. An example of a carboxylic acid is acetic acid.
Cast iron – This is iron as it comes out of the blast furnace. It contains around 4% carbon and so is brittle. Some of the carbon is removed as the cast iron is converted to steel.
Catalytic converter – This is a device fitted to the exhaust pipe of a car in order to convert the harmful gases into less harmful ones. The particular gases to be removed are carbon monoixde and the nitrogen oxides. After conversion , these become nitrogen (already 4/5 of the atmosphere) and carbon dioxide (although a pollutant since it is a greenhouse gas, the amount of carbon dioxide released in this way is very small compared to the amount emitted by burning the fuel).
Catalyst – A catalyst is a substance that lowers the activation energy of a reaction or speeds it up without being consumed by the reaction. Enzymes are proteins that act as catalysts for biochemical reactions. It can also be defined as a chemical compound used to change the rate (either to speed up or slow down) of a reaction, but is regenerated at the end of the reaction.
Cathode – A cathode is the electrode which gains electrons or is reduced. In other words, it is where reduction occurs in an electrochemical cell.
Cation – positively charged ion
Cement – Limestone is heated to a high temperature with clay and then powdered. It is mixed with sand and water to make mortar.
Cementation – This is one of the processes of sedimentary rock formation. The water is squeezed out from the gaps between the grains of sand etc of the wet sediment. This leaves behind the mineral salts which can act as a kind of glue to hold the grains together.
Read Also: Chemistry Terms and Their Meanings {A}
Centrifuge – equipment used to separate substances based on density by rotating the tubes around a centred axis
Cell potential – the force in a galvanic cell that pulls electron through reducing agent to oxidizing agent
Centrifuge – equipment used to separate substances based on density by rotating the tubes around a centred axis
Cell potential – the force in a galvanic cell that pulls electron through reducing agent to oxidizing agent
Centrifuge – equipment used to separate substances based on density by rotating the tubes around a centred axis
Cell potential – the force in a galvanic cell that pulls electron through reducing agent to oxidizing agent.
Chain reaction – A reaction whose mechanism includes one or more steps that are repeated indefinitely, until the chain is terminated, or reactants are used up.
Charles’s law – (also known as the law of volumes) is an experimental gas law which describes how gases tend to expand when heated. A modern statement of Charles’s law is. When the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be directly related.
Chemical equation – (Don’t confuse this with chemical formula) If you are asked for a symbol equation is must be balanced.
Chemical formula – (Don’t confuse this with chemical equation) This is the chemical code for a substance. If the substance forms molecules the formula tells us how many atoms of each element are in the molecule.
Eg HCl contains one hydrogen and one chlorine
C2H5OH contains two carbons, six hydrogens and one oxygen
If the substance does not form molecules (such as ionic solids), the formula tells us the ratio of each kind of ion.
Eg NaCl has one sodium ion for every chloride ion
CuCl2 has one copper ion for every two chloride ions
Sometimes brackets can be used to make things clearer:
CuNO3 2 might mean one copper, one nitrogen and thirty two oxygens but
Cu(NO3)2 clearly means one copper, two nitrogen and six oxygens
Chemical reaction – A change where one or more new substances are formed. It is difficult to undo a chemical change.
Chemical equation – A chemical equation is a description of a chemical reaction, including what reacts, what is produced, and which direction(s) the reaction proceeds.
Chelation therapy – is a chemical process in which a synthetic solution-EDTA (ethylenediaminetetraacetic acid)-is injected into the bloodstream to remove heavy metals and/or minerals from the body. Chelation means “to grab” or “to bind.”
Chemical formula – is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using a single line of chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs.
Chemical law – certain rules that pertain to the laws of nature and chemistry – examples
Chemical property – A chemical property is a property that can only be observed when a chemical change occurs. Flammability is an example of a chemical property, since you can’t measure how flammable a substance is without igniting it (making/breaking chemical bonds).
Chemical weathering – Rocks can be broken down by many effects. Chemical weathering is where this breakdown is caused by chemical action. This is often due to acidic rainfall and is made worse when the rain is made extra acidic by pollution (acid rain).
Chromatography – Literally means coloured writing, it is a technique used to separate coloured materials. You can use chromatography to separate the colours of ink (maybe black ink contains red, blue and brown dyes) or food colourings (smarties are good for this). Forensic science uses chromatography to investigate substances found at the scene of a crime and can trace DNA etc.
Closed system – is a physical system that doesn’t exchange any matter with its surroundings, and isn’t subject to any force whose source is external to the system
Coke – Coal is heated in the absence of air (so not burned) to drive off volatile components and form coke. It is a raw material in the blast furnace as a source of carbon.
Colligative properties – are properties of solutions that depend on the ratio of the number of solute particles to the number of solvent molecules in a solution, and not on the type of chemical species present.
Colloid – A colloid, in chemistry, is a mixture in which one substance of microscopically dispersed insoluble particles is suspended throughout another substance A mixture of evenly dispersed substances, such as many milks. A homogeneous, noncrystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance. Colloids include gels, sols, and emulsions; the particles do not settle and cannot be separated out by ordinary filtering or centrifuging like those in a suspension.
Combustion – This is a scientific word for the burning of a fuel. It is an exothermic reaction between an oxidant and fuel with heat and often light. Combustion is a chemical process in which a substance reacts rapidly with oxygen and gives off heat. The original substance is called the fuel, and the source of oxygen is called the oxidizer. The fuel can be a solid, liquid, or gas, although for airplane propulsion the fuel is usually a liquid.
Combustion Reaction – is a major class of chemical reactions. Combustion usually occurs when a hydrocarbon reacts with oxygen to produce carbon dioxide and water. In the more general sense, combustion involves a reaction between any combustible material and an oxidizer to form an oxidized product.
Compound – A substance containing two or more different kinds of atoms chemically joined together. A compound is an entity consisting of two or more atoms , at least two from different- elements; which associate via chemical bonds.
Compression – an area in a longitudinal wave where the particles are closer and pushed in
Concrete – This is formed by mixing cement, sand, stones (or crushed rock) and water. It can be poured into a hole to form a block for building foundations or into a mould to produce a variety of shapes (eg girders and railway sleepers). It can be reinforced by being poured around steel cables or mesh.
Covalent bond – A covalent bond is a chemical bond formed when two atoms share two electrons. Covalent bond also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding.
Condensation – is the change of the physical state of matter from gas phase into liquid phase, and is the reverse of evaporation. It is the phase change from gas to liquid. The word most often refers to the water cycle.
Conductor – is a material which contains movable electric charges. In metallic conductors, such as copper or aluminum, the movable charged particles are electrons, though in other cases they can be ions or other positively charged species.
Conjugate Acid and Base –
A Conjugate acid is within the Brønsted–Lowry acid–base theory, is a species formed by the reception of a proton (H+) by a base—in other words, it is a base with a hydrogen ion added to it. On the other hand, a conjugate base is merely what is left after an acid has donated a proton in a chemical reaction.
The conjugate base of an acid is formed when the acid donates a proton. In the equation, OH– is the conjugate base to the acid H2O because H2O donates a hydrogen ion to form OH–, the conjugate base. Note: The stronger the acid or base, the weaker the conjugate.
Cooling curve – A cooling curve is a line graph that represents the change of phase of matter, typically from a gas to a solid or a liquid to a solid. The independent variable (X-axis) is time and the dependent variable (Y-axis) is temperature.
Critical mass – Critical mass is the minimum quantity of radioactive material needed to cause a nuclear chain reaction.
Critical point – The critical point is the endpoint of the liquid-vapor line in a phase diagram, past which a super-critical liquid forms. At the critical point, the liquid and vapor phases become indistinguishable from one another.
Crystal – A crystal is an ordered, repeating three-dimensional pattern of ions, atoms, or molecules. Most crystals are ionic solids, although other forms of crystals exist. It is a solid that is packed with ions, molecules or atoms in an orderly fashion.
Cuvette – glassware used in spectroscopic experiments. It is usually made of plastic, glass or quartz and should be as clean and clear as possible.
