All chemistry definitions Grade 11

Made for RBHS

Activated complex

The unstable transition state from reactants to products in a chemical reaction.

Activation energy

The minimum energy needed for a reaction to take place.

Amphiprotic

A substance that can act as either an acid or a base; it can donate or accept a proton.

Ampholyte

A substance that can act as either an acid or a base.

Arrhenius acid

A substance that produces hydrogen ions (H⁺) when dissolved in water.

Arrhenius base

A substance that produces hydroxide ions (OH⁻) when dissolved in water.

Atomic number

The number of protons in each atom of an element; unique to each element.

Auto-ionisation

The reaction of water with itself to form H₃O⁺ and OH⁻ ions.

Avogadro's Law

One mole of any gas occupies the same volume at the same temperature and pressure.

Boiling point

The temperature at which the vapour pressure of a substance equals atmospheric pressure.

Bond energy

The energy needed to break chemical bonds to form neutral atoms.

Bond length

The average distance between the nuclei of two bonded atoms.

Bonding (shared) pair

The pair of electrons shared between two atoms in a covalent bond.

Boyle's Law

The pressure of a fixed amount of gas is inversely proportional to its volume at constant temperature.

Bronsted acid

A proton (H⁺ ion) donor.

Bronsted base

A proton (H⁺ ion) acceptor.

Capillarity

The tendency of a liquid to rise or fall in a narrow tube due to surface tension.

Chemical bonding

The mutual interaction between atoms due to attraction and repulsion between their nuclei and valence electrons.

Concentrated acid

Contains a large amount of acid (in moles) relative to the volume of water.

Concentrated base

Contains a large amount of base (in moles) relative to the volume of water.

Concentration

The number of moles of solute per cubic decimetre of solution.

Covalent bonding

The electrostatic interaction involving the sharing of electrons between atoms to form molecules.

Dative covalent bonding

A covalent bond where both shared electrons come from one atom.

Dilute acid

Contains a small amount of acid (in moles) relative to the volume of water.

Dilute base

Contains a small amount of base (in moles) relative to the volume of water.

Dipole-dipole forces

Forces between polar molecules.

Element

A collection of atoms all with the same atomic number.

Electronegativity

A measure of an atom's tendency to attract a shared pair of electrons.

Empirical formula

The simplest whole-number ratio of atoms in a compound.

Endothermic reactions

Reactions that absorb energy.

Endpoint

The point in a titration where the indicator changes colour.

Equivalence point

The point in a titration where the acid and base have completely reacted.

Exothermic reactions

Reactions that release energy.

Forces of adhesion

Forces of attraction between molecules of different substances.

Forces of cohesion

Forces of attraction between molecules of the same substance.

Heat of reaction (ΔH)

The energy absorbed or released in a chemical reaction.

Hydrogen bonds

Forces between molecules where a hydrogen atom bonded to a small, highly electronegative atom is attracted to a lone pair on a neighbouring molecule.

Hydrolysis

The reaction of a salt with water.

Induced dipole forces (London forces)

Forces between non-polar molecules.

Intermolecular forces

Forces of attraction or repulsion between molecules.

Intramolecular forces

Forces between atoms inside molecules that keep atoms together.

Ionic bonding

Electrostatic interaction between cations and anions involving electron transfer, forming a lattice structure.

Isotopes

Atoms of the same element with the same atomic number but different mass numbers.

Lone pair

A pair of valence electrons on an atom not shared with another atom.

Mass number

The total number of protons and neutrons in the nucleus of an atom.

Melting point

The temperature at which solid and liquid phases of a substance are at equilibrium.

Molar mass

The mass of one mole of a substance measured in g·mol⁻¹.

Molar Mass (M)

The mass of one mole of any substance, expressed in g·mol⁻¹.

Molecule

A neutral group of two or more atoms bonded strongly enough to act as a unit in chemical reactions.

Molecular formula

The formula showing all atoms present in a compound.

Neutralisation (Arrhenius)

The reaction where an acid and a base form a salt and water.

Neutralisation (Bronsted)

Proton transfer from an acid to a base to form the conjugate acid and conjugate base.

Non-polar (pure) covalent bond

A bond formed by equal sharing of electrons between two atoms.

One mole

The amount of substance containing the same number of particles as there are atoms in 12 g of carbon-12.

Oxidation (electron)

Loss of electrons.

Oxidation (number)

Increase in oxidation number.

Oxidising agent

A substance that is reduced (gains electrons).

pH scale

A scale from 0 to 14 measuring acidity or alkalinity of a solution.

Polar covalent bond

A bond formed by unequal sharing of electrons between two atoms.

Positive catalyst

A substance that increases the rate of a reaction without undergoing permanent change.

Pressure of a gas

A measure of the number of collisions of gas particles with each other and the container walls.

Reduction (electron)

Gain of electrons.

Reduction (number)

Decrease in oxidation number.

Reducing agent

A substance that is oxidised (loses electrons).

Relative atomic mass

The average mass of an element’s isotopes relative to ¹²C, expressed in amu.

Reversible reaction

A reaction where products can be converted back into reactants.

Redox reaction

A reaction involving electron transfer between substances.

Standard solution

A solution of known concentration.

Strong acid

An acid that ionises completely in water to form a high concentration of H₃O⁺ ions.

Strong base

A base that dissociates completely in water to form a high concentration of OH⁻ ions.

Temperature of a gas

A measure of the average kinetic energy of gas particles.

Vapour pressure

The pressure exerted by a vapour at equilibrium with its liquid in a closed system.

Weak acid

An acid that ionises partially in water to form a low concentration of H₃O⁺ ions.

Weak base

A base that ionises partially in water to form a low concentration of OH⁻ ions.