BTEC Applied Science Applications of Chemistry Revision Guide

Proton

A subatomic particle located in the nucleus carrying a relative mass of $1$ and an electrical charge of $+1$.

Neutron

An uncharged subatomic particle situated in the nucleus with a relative mass of $1$ and a relative charge of $0$.

Electron

A subatomic particle orbiting the nucleus in energy levels, possessing a relative mass of $\frac{1}{1840}$ and a relative charge of $-1$.

Atomic number ($Z$)

The total number of protons present in the nucleus of an atom, uniquely identifying the chemical element.

Mass number ($A$)

The total combined number of protons and neutrons located within an atomic nucleus.

Isotopes

Atoms of the same element containing identical numbers of protons but different numbers of neutrons.

Cation

A positively charged ion produced when a neutral atom loses one or more valence electrons.

Anion

A negatively charged ion produced when a neutral atom gains one or more valence electrons.

Ionic bond

The strong, non-directional electrostatic attraction acting between oppositely charged ions in a giant crystal lattice.

Covalent bond

The electrostatic attraction between positive atomic nuclei and a shared pair of valence electrons.

Metallic bond

The strong electrostatic attraction between a lattice of positive metal ions and a sea of delocalised electrons.

Electrical conductivity of ionic compounds

Non-conductive in solid form because ions are fixed in a lattice, but conductive when molten or aqueous because ions are free to move and carry charge.

Melting point of simple molecular substances

Relatively low because only weak intermolecular forces exist between separate molecules, requiring little energy to overcome.

Reactivity trend in Group 1 elements

Increases down the group because additional occupied electron shells increase atomic radius and electron shielding, weakening nuclear attraction on the valence electron.

Reactivity trend in Group 7 elements

Decreases down the group because greater atomic radius and electron shielding weaken the nuclear attraction needed to capture an incoming electron.

Exothermic reaction

A chemical process that releases thermal energy into the surrounding environment, increasing temperature and having $\Delta H < 0$.

Endothermic reaction

A chemical process that absorbs thermal energy from the surrounding environment, decreasing temperature and having $\Delta H > 0$.

Heat transfer equation in calorimetry

$q = mc\Delta T$, where $m$ represents mass of solution, $c$ is specific heat capacity, and $\Delta T$ is temperature change.

Collision theory

The principle stating that particles must collide with correct spatial orientation and kinetic energy at or exceeding the activation energy ($E_a$) to react.

Catalyst

A substance that speeds up a chemical reaction without undergoing permanent change, by providing an alternative route with lower activation energy ($E_a$).

Dynamic equilibrium

A state in a closed system where forward and reverse reaction rates are equal and the concentrations of reactants and products remain constant.

Le Chatelier's principle

The principle stating that when an external change in conditions is applied to a closed system at dynamic equilibrium, the position shifts to counteract that change.

Alkane

A saturated hydrocarbon consisting exclusively of single carbon-carbon bonds, conforming to the general formula $C_n H_{2n+2}$.

Alkene

An unsaturated hydrocarbon containing at least one carbon-carbon double bond, conforming to the general formula $C_n H_{2n}$.

Addition polymerisation

A process where unsaturated alkene monomers link together by breaking double bonds into single bonds without producing by-products.

Condensation polymerisation

A process where bifunctional monomers join covalently to form a polymer chain while releasing a small by-product molecule such as water ($H_2O$).

Fractional distillation

A thermal separation technique that separates crude oil hydrocarbons into fractions according to their differing boiling points along a column temperature gradient.