Cambridge IGCSE Co-ordinated Sciences (Double Award) 0654 Vocabulary

Comprehensive vocabulary flashcards covering the core definitions, scientific quantities, and measurement language from the Cambridge IGCSE Co-ordinated Sciences (Double Award) 0654 syllabus for examinations in 2025, 2026, and 2027.

Movement

An action by an organism or part of an organism causing a change of position or place.

Respiration

The chemical reactions in cells that break down nutrient molecules and release energy for metabolism.

Sensitivity

The ability to detect and respond to changes in the internal or external environment.

Growth

A permanent increase in size and dry mass.

Reproduction

The processes that make more of the same kind of organism.

Excretion

The removal of waste products of metabolism and substances in excess of requirements.

Nutrition

The taking in of materials for energy, growth and development.

Diffusion

The net movement of particles from a region of their higher concentration to a region of their lower concentration (i.e. down a concentration gradient), as a result of their random movement.

Osmosis

The net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane.

Active Transport

The movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (i.e. against a concentration gradient), using energy from respiration.

Enzyme

A protein that is involved in all metabolic reactions, where it functions as a biological catalyst.

Photosynthesis

The process by which plants synthesise carbohydrates from raw materials using energy from light.

Transpiration

The loss of water vapour from leaves.

Translocation

The movement of sucrose and amino acids in phloem from sources to sinks.

Pathogen

A disease-causing organism.

Transmissible Disease

A disease in which the pathogen can be passed from one host to another.

Active Immunity

Defence against a pathogen by antibody production in the body.

Antibody

A protein that binds to antigens leading to direct destruction of pathogens or marking of pathogens for destruction by phagocytes.

Hormone

A chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs.

Homeostasis

The maintenance of a constant internal environment.

Drug

Any substance taken into the body that modifies or affects chemical reactions in the body.

Asexual Reproduction

A process resulting in the production of genetically identical offspring from one parent.

Sexual Reproduction

A process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that are genetically different from each other.

Species

A group of organisms that can reproduce to produce fertile offspring.

Gene

A length of DNA that codes for a protein.

Allele

An alternative form of a gene.

Haploid Nucleus

A nucleus containing a single set of chromosomes.

Diploid Nucleus

A nucleus containing two sets of chromosomes.

Mitosis

Nuclear division giving rise to genetically identical cells.

Meiosis

Reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells.

Genotype

The genetic make-up of an organism in terms of the alleles present.

Phenotype

The observable features of an organism.

Homozygous

Having two identical alleles of a particular gene.

Heterozygous

Having two different alleles of a particular gene.

Dominant Allele

An allele that is expressed if it is present in the genotype.

Recessive Allele

An allele that is only expressed when there is no dominant allele of the gene present in the genotype.

Ecosystem

A unit containing the community of organisms and their environment, interacting together.

Biodiversity

The number of different species that live in an area.

Proton Number (Atomic Number)

The number of protons in the nucleus of an atom.

Mass Number (Nucleon Number)

The total number of protons and neutrons in the nucleus of an atom.

Isotopes

Different atoms of the same element that have the same number of protons but different numbers of neutrons.

Ionic Bond

A strong electrostatic attraction between oppositely charged ions.

Covalent Bond

A chemical bond formed when a pair of electrons is shared between two atoms leading to noble gas electronic configurations.

Metallic Bonding

The electrostatic attraction between the positive ions in a giant metallic lattice and a 'sea' of delocalised electrons.

Relative Atomic Mass ($A_r$)

The average mass of the isotopes of an element compared to $\frac{1}{12}\text{th}$ of the mass of an atom of $^{12}\text{C}$.

Relative Molecular Mass ($M_r$)

The sum of the relative atomic masses of the atoms in a molecule (or relative formula mass for ionic compounds).

Mole ($\text{mol}$)

The unit of amount of substance; one mole contains $6.02 \times 10^{23}$ particles (the Avogadro constant).

Electrolysis

The decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current.

Activation Energy ($E_a$)

The minimum energy that colliding particles must have to react.

Oxidation

The gain of oxygen, loss of electrons, or an increase in oxidation number.

Reduction

The loss of oxygen, gain of electrons, or a decrease in oxidation number.

Amphoteric Oxides

Oxides that react with acids and with bases to produce a salt and water.

Hydrocarbon

A compound that contains hydrogen and carbon only.

Homologous Series

A family of similar compounds with similar chemical properties that have the same general formula and display a trend in physical properties.

Polymers

Large molecules built up from many smaller molecules called monomers.

Nylon

A synthetic polyamide condensation polymer formed with alternating monomer blocks linked by amide bonds.

Scalar Quantity

A quantity that has magnitude (size) only.

Vector Quantity

A quantity that has magnitude and direction.

Speed

Distance travelled per unit time; defined by the equation $v = \frac{s}{t}$.

Velocity

Speed in a given direction.

Acceleration

Change in velocity per unit time; defined by the equation $a = \frac{\Delta v}{\Delta t}$.

Gravitational Field Strength ($g$)

The gravitational force per unit mass; defined by $g = \frac{W}{m}$, which is approximately $9.8\,N/kg$ near the surface of the Earth.

Density ($\rho$)

Mass per unit volume; defined by the equation $\rho = \frac{m}{V}$.

Spring Constant ($k$)

Force per unit extension; defined by the equation $k = \frac{F}{x}$.

Moment of a Force

A measure of the turning effect of a force; defined as $\text{moment} = \text{force} \times \text{perpendicular distance from the pivot}$.

Power

Work done per unit time or energy transferred per unit time; defined by $P = \frac{W}{t}$ or $P = \frac{\Delta E}{t}$.

Pressure ($p$)

Force per unit area; defined by the equation $p = \frac{F}{A}$.

Refraction

The change in direction of a light ray passing from one medium to another.

Refractive Index ($n$)

The ratio of the speeds of a wave in two different regions; calculated as $n = \frac{\sin(i)}{\sin(r)}$.

Critical Angle

The angle of incidence at which the angle of refraction is $90^\circ$ and above which all light is totally internally reflected.

Ultrasound

Sound with a frequency higher than $20\,kHz$.

Electric Current ($I$)

The charge passing a point per unit time; defined by the equation $I = \frac{Q}{t}$.

Electromotive Force (e.m.f.)

The electrical work done by a source in moving a unit charge around a complete circuit, measured in volts ($V$).

Potential Difference (p.d.)

The work done by a unit charge passing between two points in a circuit, measured in volts ($V$).

Half-Life

The time taken for half the nuclei of a particular isotope in any sample to decay.

True Value

The value that would be obtained in an ideal measurement.

Measurement Error

The difference between a measured value and the true value of a quantity.

Accuracy

A measurement result is described as accurate if it is close to the true value.

Precision

How close the measured values of a quantity are to each other.

Repeatability

A measurement is repeatable if the same or similar result is obtained when the measurement is repeated under the same conditions, using the same method, within the same experiment.

Reproducibility

A measurement is reproducible if the same or similar result is obtained when the measurement is made under either different conditions or by a different method or in a different experiment.

Independent Variable

The variables that are changed in a scientific experiment by the scientist.

Dependent Variable

The variables that are observed or measured in a scientific experiment, which may change based on changes made to the independent variables.