ECZ Grade 11 Chemistry Summarised Notes

These vocabulary flashcards provide definitions for key terms found in the ECZ Grade 11 Chemistry notes, covering periodic table trends, stoichiometry, gas laws, thermodynamics, and electrochemistry.

Group

A vertical column of elements in the periodic table.

Valency electron

The electron in the outermost shell of an atom that controls its chemical reactions.

Halogens

The elements in Group 7 of the periodic table, which are coloured, have seven valency electrons, and act as oxidizing agents.

Noble gases

Group 8 (0) elements that are unreactive because they have full electron shells; they are all colourless gases at RTP.

Period

A horizontal row in the periodic table; elements in a period have the same number of electron shells.

Metalloids

Elements like silicon ($Si$) that lie on the dividing line between metals and non-metals and have properties of both.

Amphoteric oxides

Oxides, such as aluminium oxide ($Al_2O_3$), that react with both acids and bases to give a salt and water.

Neutral oxides

Oxides that have neither acidic nor basic properties and do not react with acids or bases to form salts, such as water ($H_2O$), nitrogen monoxide ($NO$), and carbon monoxide ($CO$).

Law of constant composition

States that all samples of a pure compound contain the same elements in the same atomic ratio and proportions by mass.

Empirical formula

The formula showing the simplest whole number ratio of the atoms present in a compound.

Molecular formula

The formula showing the actual number of each atom present in a molecule.

Mole

A quantity of a chemical substance containing $6.022 \times 10^{23}$ particles.

Avogadro constant ($L$)

The number of particles in one mole of a substance, approximately equal to $6 \times 10^{23}$, or more precisely $6.022 \times 10^{23}$.

Concentration

The mass or number of moles of solute divided by the volume of the solution, usually expressed in $g/dm^3$ or $mol/dm^3$.

Titration

A technique used to find the concentration of a solution by reacting a fixed volume of it with a solution of known concentration.

End-point

The point in a titration where the indicator just changes colour, signalling that the reaction is complete.

Avogadro’s Law

States that equal volumes of gases, at the same temperature and pressure, contain equal numbers of molecules.

Molar volume ($V_m$)

The volume occupied by one mole of any gas under specific conditions of temperature and pressure.

Boyle’s Law

States that if the temperature is constant, the volume ($V$) and pressure ($P$) of a gas are inversely proportional ($P \times V = \text{constant}$).

Charles’ Law

States that if the pressure of a gas is constant, the volume of the gas is directly proportional to the absolute temperature ($V \times T$).

Absolute temperature

Temperature measured in Kelvin ($K$), where $T(K) = T(^\text{o}C) + 273$.

Standard Temperature and Pressure (STP)

Conditions defined as a pressure of $10^5 Pa$ and a temperature of $273 K$, where the molar gas volume is $22.4 dm^3$.

Room Temperature and Pressure (RTP)

Conditions defined as a pressure of $10^5 Pa$ and a temperature of $298 K$, where the molar gas volume is taken as $24.0 dm^3$.

Molar gas constant ($R$)

The constant in the ideal gas equation ($pV_m = RT$) with a value of $8.314 J K^{-1} mol^{-1}$.

Enthalpy ($H$)

The heat content of a system; the change in heat content is represented by \text{\Delta}H.

Exothermic reaction

A reaction in which heat is given out to the surroundings, resulting in a negative \text{\Delta}H.

Endothermic reaction

A reaction in which heat is absorbed from the surroundings, resulting in a positive \text{\Delta}H.

Hess’s Law

States that the overall energy change in converting reactants to products is the same regardless of the route taken.

Activation energy

The additional energy that a reacting system must gain before the final products can be formed.

Rate of reaction

The speed of a reaction stated in terms of grams per second ($g/s$) or moles per second ($mol/s$) of reactant used or product produced.

Catalyst

A substance that changes the speed of a chemical reaction but remains unchanged in mass at the end of the reaction by providing a lower activation energy path.

Reversible reaction

A reaction that can proceed in both the forward and backward directions, represented by the symbol $\rightleftharpoons$.

Dynamic equilibrium

A state in a reversible reaction where the rate of the forward reaction equals the rate of the backward reaction, resulting in no further change in concentration.

Contact Process

The industrial process used to manufacture sulphuric acid from sulphur.

Haber Process

The industrial process used to manufacture ammonia from nitrogen and hydrogen using an iron catalyst, $400^\text{o}C$, and $250$ atmospheres of pressure.

Fuel

A substance that burns in air to provide useful energy.

Heat of combustion

The total amount of heat released when one mole of a fuel is completely burned in air or oxygen.

Fractional distillation

A process used to separate a mixture of volatile liquids based on their different boiling points.

Nuclear fission

A process where a heavy nucleus, such as $^{235}U$, breaks into smaller nuclei when struck by a neutron, releasing enormous amounts of energy.

Oxidation

The gain of oxygen, the removal of hydrogen, or the loss of one or more electrons by a substance.

Reduction

The removal of oxygen, the addition of hydrogen, or the gain of one or more electrons by a substance.

Redox reaction

A chemical reaction involving both reduction and oxidation occurring simultaneously.

Oxidising agent

A reagent that causes oxidation in another substance and is itself reduced during the process.

Reducing agent

A reagent that causes reduction in another substance and is itself oxidised during the process.

Corrosion

The oxidation of a metal, such as the rusting of iron, which requires both moisture and oxygen.

Electrolysis

The process by which an electric current flows through a liquid (electrolyte) to produce a chemical change.

Electrolyte

A liquid or solution that contains ions and can conduct electricity, resulting in chemical decomposition at the electrodes.

Anode

The positive electrode in an electrolytic cell where oxidation occurs.

Cathode

The negative electrode in an electrolytic cell where reduction occurs.

Faraday constant ($F$)

The amount of charge carried by one mole of electrons, equal to approximately $9.65 \times 10^4 C$.

Acid

A proton donor that reacts with a base to form a salt and water.

Base

A proton acceptor that reacts with an acid to form a salt and water.

Salt

A compound formed when the hydrogen ions of an acid are replaced by metal ions or ammonium ions.

Acid salt

A salt that contains replaceable hydrogen atoms.

Hydrolysis

The reaction of an ion or molecule with water, often resulting in an acidic or alkaline solution.