BCS Written General Science & Tech key terms

The net force on an object equals its mass multiplied by the acceleration produced, so a heavier body needs a larger force to gain the same acceleration.

The tendency of a body to resist any change in its state of rest or uniform motion unless an external force acts on it; it depends on mass.

Work is done when a force moves an object through a distance; energy is the capacity to do that work, measured in joules and conserved in closed systems.

The time taken for half the atoms of a radioactive sample to decay, or half the amount of a substance to be removed or broken down in a process.

Spontaneous emission of alpha particles, beta particles or gamma rays from unstable atomic nuclei as they change towards a more stable arrangement, releasing energy.

One of two or more forms of the same chemical element whose atoms have equal numbers of protons but different numbers of neutrons, giving different atomic masses.

The amount of a substance containing exactly the same number of elementary particles as there are atoms in twelve grams of carbon-12, about 6.02 times ten to the twenty-third.

An acid donates hydrogen ions in solution while a base accepts them; their relative strength is shown by the pH scale and they neutralise each other to form salt and water.

A logarithmic scale from zero to fourteen expressing the acidity or alkalinity of a solution, where seven is neutral, below seven is acidic and above seven is basic.

A tabular arrangement of the elements in order of increasing atomic number, grouped by recurring chemical properties so that elements in the same column behave similarly.

The process by which green plants and algae use sunlight, water and carbon dioxide to make glucose and release oxygen, with chlorophyll absorbing the light energy in chloroplasts.

The set of reactions in cells that break down glucose, with or without oxygen, to release energy stored as ATP, producing carbon dioxide and water as waste.

A protein that speeds up a specific biochemical reaction by binding its substrate at an active site; activity is sensitive to temperature and pH.

The double-stranded molecule that stores genetic instructions in the sequence of its bases, which is copied before cell division and read to build proteins.

A length of DNA that carries the instructions for making a particular protein or functional molecule, and which is passed from parents to offspring.

A permanent change in the base sequence of DNA, which may arise spontaneously or from exposure to radiation or chemicals and may alter the resulting protein.

The process by which individuals with inherited traits that improve survival and reproduction leave more offspring, so those traits become more common over generations.

The body's network of cells, tissues and organs that recognises foreign or abnormal material and defends against infection, and which can remember past pathogens.

Deliberate exposure to a harmless form or component of a pathogen so the immune system builds memory cells, giving protection against later infection by that pathogen.

Indirect protection of unvaccinated people that arises when a large enough share of a population is immune, so a pathogen cannot spread easily through the group.

A rise in cases of a disease above what is normally expected in a defined community or region; when it spreads across continents it is called a pandemic.

An illness spread by an organism such as a mosquito, tick or fly that carries a pathogen from one host to another, for example malaria or dengue.

A positional number system using only the digits zero and one, in which each place value is a power of two; it is the basis of digital data representation.

A bit is a single binary digit, either zero or one; a byte is a group of eight bits, the usual unit for storing one character or a small value.

A finite, unambiguous sequence of steps that takes an input and produces a required output, forming the logical basis of any computer program.

Converting readable data into an unreadable form using a key, so that only someone holding the correct key can reverse the process and recover the original message.

An organised collection of stored data structured so that it can be searched, updated and retrieved efficiently, usually managed by dedicated software.

Energy drawn from sources that are naturally replenished on a human timescale, such as sunlight, wind, flowing water and biomass, unlike finite fossil fuels.

The ratio of useful output to total input for a machine or process, usually expressed as a percentage; the remainder is lost, often as waste heat.

A material whose electrical conductivity lies between that of a conductor and an insulator and can be controlled by doping or applied voltage, enabling transistors and chips.

Computer systems that perform tasks normally needing human intelligence, such as pattern recognition, language understanding and decision-making, by learning from data.

A testable, falsifiable statement predicting a relationship between variables, proposed as a provisional explanation and checked against evidence gathered by observation or experiment.

A study in which all variables except the one being tested are kept constant, and a comparison group receives no treatment, so that effects can be attributed to the tested factor.

Independent scrutiny of a research report by experts in the same field before publication, intended to check methods, evidence and interpretation for quality and honesty.

Warming of a planet's surface caused by gases such as carbon dioxide and methane trapping outgoing heat radiation, which keeps Earth habitable but intensifies with added emissions.

The variety of living species, their genetic differences and the ecosystems they form; it supports ecosystem services and makes natural systems more resilient to change.

Meeting present needs without compromising the ability of future generations to meet theirs, balancing economic growth with environmental protection and social equity.

The policy that where an activity may cause serious or irreversible harm, lack of full scientific certainty should not delay cost-effective measures to prevent it.