Edexcel GCSE Chemistry Key Terms

A substance that is dissolved in water to form a solution.

A state of matter where a substance is dissolved in water, allowing soluble ionic compounds to separate into their constituent ions.

The process of using basic mathematics and atom tallying to balance a chemical equation by inspection.

A chemical equation in which the number of atoms of each element is identical on both the reactant and product sides.

A representation of a substance using symbols for its constituent elements and subscripts to show the ratio of atoms.

A process where atoms in reactants are rearranged to form new substances (products).

The large number placed in front of a chemical formula in an equation, representing the molar ratio.

The large numbers placed in front of a chemical formula in an equation to represent the number of moles or molecules of that substance.

A principle stating that no atoms are lost or made during a chemical reaction, so the mass of the products equals the mass of the reactants.

A substance that can destroy living tissue (such as skin and eyes) and attack or chemically eat through metals.

A molecule containing exactly two atoms chemically bonded together.

Elements that exist naturally as pairs of atoms bonded together when not part of a compound (e.g., O₂, H₂, Cl₂).

The process by which an ionic compound separates into its constituent ions when dissolved in water.

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

A substance that is hazardous to the aquatic environment and can cause long-term damage to ecosystems.

An intermediate equation that shows all soluble ionic compounds dissociated into their constituent ions before spectator ions are removed.

A substance that may explode due to shock, friction, fire, or heat.

A substance that ignites and catches fire easily.

A ventilated enclosure in a laboratory that draws harmful vapours and gases away from the user to prevent inhalation.

A gas stored in a container that may explode if it is heated.

Personal protective equipment worn on the hands to create a physical barrier against corrosive or toxic substances.

An inherent property of a substance, process, or piece of equipment that has the potential to cause harm.

Standardised pictograms placed on chemical containers to provide a universal, rapid method of communicating the specific dangers of a substance.

A substance that poses serious long-term health risks, such as carcinogenicity or specific organ damage.

A simplified chemical equation that shows only the reacting particles (ions or molecules) that undergo a chemical change, with spectator ions excluded.

A chemical formula representing the simplest whole-number ratio of ions in an ionic compound, where the total net charge is zero.

A substance that causes slight inflammation or discomfort to the body, often a dilute version of a corrosive chemical.

The scientific principle stating that no atoms are created or destroyed during a chemical reaction, meaning the total mass of reactants must equal the total mass of products.

A substance that causes less severe hazards, such as skin or eye irritation, represented by an exclamation mark.

The mathematical ratio between the amounts in moles of any two compounds in a chemical reaction, directly matching the coefficients of the balanced equation.