OCR GCSE Combined Science A key terms

A separation method in which suspended insoluble particles settle to the bottom of water left standing.

The process in which humans choose organisms with desirable inherited characteristics as parents, then select and breed suitable offspring over many generations. Also called artificial selection.

A valve at the exit of a ventricle that prevents blood flowing back from the aorta or pulmonary artery when the ventricle relaxes.

A nerve cell that carries electrical impulses from receptors towards the central nervous system.

A cell or sense organ that detects a stimulus.

The wall separating the right and left sides of the heart, preventing oxygenated and deoxygenated blood from mixing.

A circuit in which components are connected along one path, so the same current passes through them.

The solid material that settles out of sewage during sedimentation.

A chromosome involved in determining biological sex. In humans, the sex chromosomes are X and Y.

An infection that can pass between people through sexual contact.

Two electrons shared between atoms to form a covalent bond.

Material placed between a radiation source and an object or person to absorb radiation and reduce exposure.

The internationally agreed system of measurement units, including the metre (m), kilogram (kg) and second (s).

One of the seven units from which other SI units can be formed, such as the second or kilogram.

A perforated end wall between sieve-tube elements, allowing dissolved substances to flow from one element to the next.

A living, elongated phloem cell joined end to end with others to form a transport tube; it has little cytoplasm and no nucleus.

A digit counted when expressing how precisely a numerical value is stated. Count from the first non-zero digit, including zeros between significant digits and any final zeros explicitly indicating precision.

Separation and collection of a liquid by vaporising it and then condensing its vapour.

A substance made of separate, small molecules, with covalent bonds within each molecule and intermolecular forces between molecules.

Inheritance of a characteristic controlled by one gene.

A part of a plant that removes sugars from the phloem to use or store them, such as a growing root tip or developing fruit.

A unit belonging to the International System of Units, such as the metre (m), kilogram (kg) or second (s).

A consequence for communities or society, such as changes in access to food or protection from disease.

A wire wound into a long coil of many turns that produces a magnetic field when a current flows through it.

A state of matter with a fixed shape and volume; its particles are close together and vibrate about fixed positions.

The substance that dissolves in a solvent to form a solution.

A mixture formed when a solute dissolves in a solvent.

A liquid in which a solute dissolves.