OCR GCSE Combined Science A key terms

A biological molecule belonging to a group that includes fats and oils. Lipids act as energy stores and form part of cell membranes.

A state of matter with a fixed volume but no fixed shape; its closely spaced particles move past one another.

The mains conductor at a nominal alternating potential difference of about 230 V relative to earth in the UK.

The variety of species within a particular geographical area, such as a pond or nature reserve.

A chemical used after chromatography to make the positions of colourless substances visible.

A simplified model of enzyme action in which a substrate fits an enzyme’s active site like a key fits a lock.

A scale on which equal numerical steps represent equal multiplication factors rather than equal amounts added. Each one-unit change in pH represents a tenfold change in hydrogen ion concentration.

A pair of outer-shell electrons that is not shared in a covalent bond.

A wave in which vibrations are parallel to the direction of wave travel.

An energy resource that produces relatively little greenhouse gas emission per unit of energy supplied. Nuclear power, wind, solar and hydroelectricity are examples; low-carbon does not mean completely emission-free.

Rock containing a relatively low proportion of the metal or metal compound being extracted.

The use of a substance such as oil or grease between moving surfaces to reduce friction.

The hollow central space inside a tube, such as a xylem vessel.

A hormone released by the pituitary gland that triggers ovulation.

A white blood cell involved in specific immunity; B-lymphocytes produce antibodies.

An enzyme found in tears that breaks down and kills bacteria.

The angle that a magnetic field makes with the horizontal; also called magnetic inclination.

A position on Earth’s surface where the magnetic field is vertical.

A region in which a magnet or current-carrying conductor can experience a magnetic force.

A line drawn to represent a magnetic field. Its arrow shows the field direction, and closer spacing between lines represents a stronger field.

A measure of magnetic field strength, represented by $B$ and measured in tesla (T).

An attractive or repulsive force between magnetic poles.

A material that is attracted to a magnet and can become magnetised, such as iron, cobalt or nickel.

Either end of a magnet, where its magnetic field is strongest. A magnet has a north pole and a south pole.

How many times larger an image is than the object it represents.

The size of a quantity, without its direction or sign.

The electricity supply delivered to buildings through the National Grid, used to power appliances plugged into sockets.