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

Essential definitions and vocabulary covering Biology, Chemistry, Physics, and experimental terms from the Cambridge IGCSE Co-ordinated Sciences (0654) syllabus.

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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.

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 (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 (against a concentration gradient), using energy from respiration.

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.

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.

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.

Ecosystem

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

Biodiversity

The number of different species that live in an area.

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.

Homologous series

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

Polymers

Large molecules built up from many smaller molecules called monomers.

Structure of nylon (polyamide)

A polyamide polymer chain consisting of alternating dicarboxylic acid and diamine monomer blocks connected together by amide links ($-\text{CO}-\text{NH}-$).

Scalar quantity

A physical quantity that has magnitude (size) only.

Vector quantity

A physical quantity that has both magnitude and direction.

Velocity

Speed in a given direction.

Acceleration

Change in velocity per unit time ($a = \frac{\Delta v}{\Delta t}$).

Gravitational field strength ($g$)

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

Density ($\rho$)

Mass per unit volume ($\rho = \frac{m}{V}$).

Spring constant ($k$)

Force per unit extension ($k = \frac{F}{x}$).

Moment of a force

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

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 $20\,\text{kHz}$.

Electric field

A region in which an electric charge experiences a force.

Electric current ($I$)

The charge passing a point per unit time ($I = \frac{Q}{t}$).

Electromotive force (e.m.f.)

The electrical work done by a source in moving a unit charge around a complete circuit.

Potential difference (p.d.)

The work done by a unit charge passing between two points in a circuit.

Half-life

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

Light-year

The distance travelled in the vacuum of space by light in one year.

Accuracy

A description of a measurement result indicating that it is close to the true value.

Precision

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

Repeatability

The condition where 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

The condition where 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.