OCR GCSE Chemistry A key terms

The change in the amount of a reactant used up or product formed per unit time.

A comparison found by dividing one quantity by another quantity measured in the same units.

A natural material obtained for use in making a product.

A substance present at the start of a chemical reaction and changed during the reaction.

A factor deliberately set or changed during a reaction, such as temperature, concentration, gas pressure or the surface area of a solid.

A reaction or sequence of reactions used to make a specified product.

A diagram showing how energy changes as reactants become products.

How readily a substance undergoes a chemical reaction; for a metal, this is linked to how readily its atoms lose electrons and form positive ions.

An arrangement of metals from most reactive to least reactive.

A chemical added to a sample to produce an observable reaction that helps identify a substance.

Changing the form of an equation without changing the relationship it represents.

Changing the form of an equation without changing the relationship it expresses.

Processing waste material so that it can be used to make a new product.

A reaction in which oxidation and reduction happen together as electrons are transferred between species.

A substance that causes another substance to be reduced by removing oxygen from it.

The gain of electrons by a substance.

The distinctive result produced by a known substance and used to help identify it.

A substance or result with known properties that is used for comparison with an unknown sample.

A measure of how much of an ion is detected compared with other ions in the same spectrum.

The weighted mean mass of an atom of an element compared with one-twelfth of the mass of a carbon-12 atom.

The weighted mean mass of an atom of an element compared with one-twelfth of the mass of a carbon-12 atom.

The average mass of an atom of an element compared with one-twelfth of the mass of a carbon-12 atom.

The sum of the relative atomic masses of every atom represented in a chemical formula.

The sum of the relative atomic masses of all the atoms represented by a chemical formula.

The relative mass of a molecule, found by adding the relative atomic masses of all the atoms shown in its molecular formula.

A value calculated as 1 divided by the time taken to reach the same endpoint in each trial; it is proportional to the reaction rate.

A value that compares a particle's charge or mass with an agreed reference value rather than giving its absolute measurement.