OCR GCSE Combined Science B key terms

The transfer of energy from an electromagnetic wave to matter.

The number of organisms of a particular species in a habitat or defined area.

The rate of change of velocity, measured in metres per second squared (m/s²).

The acceleration of an object in free fall, represented by $g$. Near Earth's surface it is approximately $9.8\text{ m/s}^2$ downwards.

How close a measurement is to the true value of the quantity being measured.

A substance that produces hydrogen ions, $\mathrm{H^+}$, in aqueous solution.

Rain made more acidic by atmospheric pollutants, particularly sulfur dioxide and oxides of nitrogen.

The minimum energy that reacting particles need for a successful collision and a reaction to occur.

The region of an enzyme where a substrate binds and the reaction takes place.

The movement of a substance across a cell membrane from a lower concentration to a higher concentration, against its concentration gradient, using energy supplied by respiration.

The number of nuclear decays in a radioactive sample per second, measured in becquerels (Bq).

An adjustment that reduces the harm caused by actual or expected climate change.

A hormone secreted by the adrenal glands that prepares the body for rapid action in a threatening or stressful situation, producing the fight-or-flight response.

A stem cell found in a body tissue that can differentiate into a limited range of related specialised cells.

Introducing air into water, for example to provide oxygen for bacteria that break down organic waste.

Respiration that uses oxygen to break down glucose completely, producing carbon dioxide and water and a relatively large yield of ATP.

A soluble base that produces hydroxide ions, $\mathrm{OH^-}$, in aqueous solution.

A Group 1 metal, such as lithium, sodium or potassium, that reacts with water to form an alkaline metal hydroxide solution and hydrogen.

A hydrocarbon with only single bonds between its carbon atoms.

A hydrocarbon containing a carbon–carbon double bond, $\mathrm{C=C}$.

An alternative version of a gene.

One of two or more different structural forms of the same element in the same physical state.

A particle containing two protons and two neutrons: a helium nucleus with charge $+2e$.

An electric current that repeatedly reverses direction.

A voltage whose polarity repeatedly reverses, alternating between positive and negative values.

A small biological molecule that can be joined to others to form a protein. Amino acids contain nitrogen as well as carbon, hydrogen and oxygen.

An instrument that measures current and is connected in series with the component being investigated.