AQA GCSE Combined Science & Separate Sciences Comprehensive Revision

Complete vocabulary flashcard deck covering GCSE Physics, Chemistry, and Biology modules across Atomic Structure, Electricity, Energy, Particle Model of Matter, Chemical Changes, Bioenergetics, Cells, Infection and Response, and Organ Systems.

Activity (Radioactive decay)

The rate at which a source of unstable nuclei decays, measured in becquerels ($\text{Bq}$).

Count-rate

The number of radioactive decays recorded each second by a detector (such as a Geiger-Muller tube).

Alpha particle ($\alpha$)

A radiation particle emitted from the nucleus consisting of $2$ protons and $2$ neutrons (identical to a helium nucleus), carrying a $+2$ charge.

Beta particle ($\beta$)

A high-speed electron emitted from the nucleus when a neutron turns into a proton, carrying a $-1$ charge.

Gamma ray ($\gamma$)

Electromagnetic radiation emitted from the nucleus that has no mass and no electrical charge.

Half-life

The time it takes for the number of nuclei of a radioactive isotope in a sample to halve, or the time it takes for the count rate from a sample to fall to half of its initial level.

Radioactive contamination

The unwanted presence of materials containing radioactive atoms on other materials or in contact with an object or person.

Irradiation

The process of exposing an object or person to nuclear radiation without the radioactive material coming into contact with the object.

Nuclear fission

The splitting of a large, unstable atomic nucleus (such as uranium or plutonium) into two smaller nuclei, releasing two or three neutrons along with energy.

Nuclear fusion

The joining of two small (light) nuclei to form a single heavier nucleus, converting a small amount of mass into a large release of energy.

Electric current

The rate of flow of electrical charge (usually electrons) around a closed circuit, measured in amperes ($\text{A}$).

Potential difference

Also called voltage; the difference in electrical potential between two points in a circuit that causes electric current to flow.

Electrical resistance

Anything that opposes or slows the flow of electrical charge in a circuit, usually caused by electrons colliding with ions in the material.

Ohm's Law

The principle stating that the current through an ohmic conductor at a constant temperature is directly proportional to the potential difference across it ($V = I \times R$).

Diode

A circuit component that allows electric current to flow in one direction only, having high resistance in the reverse direction.

Light Dependent Resistor (LDR)

A resistor whose resistance decreases as the light intensity falling on it increases.

Thermistor

A temperature-dependent resistor whose electrical resistance decreases as its temperature increases.

The National Grid

A nationwide system of cables and transformers connecting power stations directly to consumers such as homes, shops, and factories.

Step-up transformer

A device used in the National Grid to increase the potential difference and decrease the current from power stations to transmission cables, reducing heat loss in wires.

Electric field

The region around a charged object or particle within which a force is exerted on another charged object or particle.

Specific Heat Capacity ($c$)

The amount of energy required to raise the temperature of $1\,\text{kg}$ of a substance by $1\,^{\circ}\text{C}$.

Power

The rate at which energy is transferred or the rate at which work is done, calculated as $P = \frac{E}{t}$ and measured in watts ($\text{W}$) or joules per second ($\text{J/s}$).

Closed energy system

A system where energy can be transferred between stores, but no mass enters or leaves and there is no net change to the total energy.

Efficiency

The ratio of useful output energy transfer to total input energy transfer, often expressed as a percentage: $\text{Efficiency} = \frac{\text{Useful output energy}}{\text{Total input energy}}$.

Renewable energy resource

An energy source that can be replenished as it is used and will therefore not run out (e.g., solar, wind, hydro-electric, tidal, geothermal, biomass).

Density ($\rho$)

The mass of a given volume of a substance, calculated using the equation $\rho = \frac{m}{V}$ ($\text{kg/m}^3$).

Internal energy

The total energy stored by the particles within a system, made up of the sum of their individual kinetic and potential energies.

Specific latent heat

The amount of energy required to change the state of $1\,\text{kg}$ of a substance with no change in temperature.

Specific latent heat of fusion ($L_f$)

The energy required to change $1\,\text{kg}$ of a substance from a solid to a liquid (or vice versa) without altering its temperature.

Specific latent heat of vaporisation ($L_v$)

The energy required to change $1\,\text{kg}$ of a substance from a liquid to a gas (or vice versa) without altering its temperature.

Compound

A substance containing two or more different elements chemically combined in fixed proportions that cannot be separated by physical means.

Filtration

A separation technique that separates substances that are insoluble in a solvent from those that are soluble.

Crystallisation

A separation method used to produce solid crystals from a solution by gently heating and evaporating the solvent.

Simple distillation

A technique used to separate a volatile solvent from a mixture by evaporation followed by condensation.

Fractional distillation

A separation process that separates miscible liquids with different boiling points by evaporating and condensing them across a temperature gradient.

Plum pudding model

J.J. Thomson's model of the atom as a sphere of positive charge with negatively charged electrons embedded evenly throughout it.

Isotopes

Atoms of the same element that contain the same number of protons but different numbers of neutrons.

Alkali metals

The Group 1 elements; soft, highly reactive metals that have one electron in their outer shell and increase in reactivity down the group.

Halogens

The Group 7 elements; toxic non-metals that form diatomic molecules, have seven outer electrons, and decrease in reactivity down the group.

Noble gases

The unreactive Group 0 elements that have complete outer electron shells and exist as single atoms.

Catalyst

A chemical substance that increases the rate of a chemical reaction without being used up or altered in the process.

Ionic bonding

The electrostatic attraction between oppositely charged ions formed by the transfer of electrons from a metal atom to a non-metal atom.

Covalent bond

A strong chemical bond formed when non-metal atoms share one or more pairs of electrons.

Metallic bonding

The strong electrostatic attraction between positive metal ions arranged in layers and a shared sea of delocalised electrons.

Delocalised electrons

Electrons that are free to move throughout an entire structure and are not associated with any single atom or covalent bond.

Alloy

A mixture of two or more elements where at least one is a metal; harder than pure metals because different-sized atoms distort regular layers.

Polymer

A substance composed of very large molecules made up of many small repeating reactive units (monomers) joined by strong covalent bonds.

Graphene

A single layer of graphite consisting of interlocking hexagonal rings of carbon atoms that is one atom thick, lightweight, strong, and highly conductive.

Fullerenes

Molecules of carbon atoms arranged into hollow shapes, predominantly consisting of hexagonal rings with some pentagonal or heptagonal rings.

Carbon nanotubes

Cylindrical fullerenes with extremely high length-to-diameter ratios, providing high tensile strength and electrical conductivity.

Nanoparticles

Particles ranging from $1$ to $100\,\text{nm}$ in size, possessing a very high surface area to volume ratio compared to the same bulk materials.

Ore

A rock that contains enough metal compound to make it economically worthwhile to extract the metal.

Oxidation (electronic definition)

The loss of electrons by an atom or ion during a chemical reaction ($\text{OIL}$).

Reduction (electronic definition)

The gain of electrons by an atom or ion during a chemical reaction ($\text{RIG}$).

Electrolysis

The chemical breakdown of an ionic compound into elements by passing an electric direct current through an electrolyte.

Electrolyte

A molten ionic compound or aqueous solution containing free-moving ions that conducts electricity during electrolysis.

Strong acid

An acid that completely ionises in aqueous solution to release hydrogen ions ($H^+$), such as hydrochloric acid ($HCl$).

Weak acid

An acid that only partially ionises in aqueous solution, such as ethanoic acid ($CH_3COOH$).

Titration

A quantitative chemical method used to measure the exact volumes of acid and alkali solutions required to neutralise each other.

Exothermic reaction

A reaction that transfers energy to the surroundings, causing the temperature of the surroundings to increase.

Endothermic reaction

A reaction that takes in energy from the surroundings, causing the temperature of the surroundings to decrease.

Activation energy

The minimum amount of energy that colliding particles must possess in order to react.

Fuel cell

An electrochemical cell supplied continuously by an external fuel source (such as hydrogen) and oxygen, oxidising the fuel to generate a potential difference.

Photosynthesis

An endothermic process in which plants convert carbon dioxide and water into glucose and oxygen using light energy absorbed by chlorophyll.

Limiting factor

An environmental condition or resource that restricts the rate of a physiological reaction when it is in short supply.

Aerobic respiration

An exothermic cellular reaction that uses oxygen to completely break down glucose, yielding carbon dioxide, water, and large amounts of energy.

Anaerobic respiration

An exothermic cellular process that transfers energy from glucose without oxygen, producing lactic acid in animals or ethanol and carbon dioxide in yeast.

Fermentation

Anaerobic respiration in yeast cells that converts glucose into ethanol and carbon dioxide, economically vital for bread and alcoholic beverages.

Oxygen debt

The amount of extra oxygen required after vigorous exercise to oxidise accumulated lactic acid in the liver and convert it back to glucose.

Metabolism

The sum of all enzyme-controlled chemical reactions occurring continuously in a cell or the whole body.

Eukaryotic cells

Complex cells that contain a cell membrane, cytoplasm, and genetic material enclosed within a membrane-bound nucleus (e.g., animal and plant cells).

Prokaryotic cells

Small, simple cells lacking a nucleus, in which DNA exists as a single loop and as smaller rings called plasmids (e.g., bacterial cells).

Cell differentiation

The developmental process by which an unspecialised cell acquires sub-cellular structures to become specialised for a specific function.

Resolution

The shortest distance between two points on a specimen that can still be distinguished as separate entities under a microscope.

Mitosis

A stage in the cell cycle where a duplicated set of chromosomes divides to produce two genetically identical daughter cells for growth and repair.

Stem cell

An undifferentiated cell capable of giving rise to more stem cells of the same type or differentiating into specialised cell types.

Meristem

Plant tissue found at the growing tips of roots and shoots containing undifferentiated stem cells that can divide throughout the plant's life.

Diffusion

The spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration down a concentration gradient.

Osmosis

The net diffusion of water molecules from a dilute solution to a concentrated solution across a partially permeable membrane.

Active transport

The movement of substances from a more dilute solution to a more concentrated solution against a concentration gradient, requiring energy from respiration.

Pathogen

A micro-organism (such as a bacterium, virus, fungus, or protist) that causes infectious communicable disease in plants or animals.

Antigen

A specific protein found on the surface of a pathogen that triggers an immune response by white blood cells.

Antibody

A protective protein produced by white blood cells (lymphocytes) that targets and binds specifically to complementary antigens on a pathogen.

Vaccine

A preparation containing dead or inactive forms of a pathogen introduced to stimulate white blood cells to produce specific antibodies safely.

Antibiotic

A medicine (such as penicillin) that cures bacterial disease by killing infectious bacteria inside the body without damaging body cells.

Placebo

An inactive substance designed to look like the drug being tested in a clinical trial to ensure any observed improvement is due solely to the active drug.

Monoclonal antibodies

Antibodies produced from a single clone of hybridoma cells, designed to target and bind to one specific chemical or antigen site.

Chlorosis

The yellowing of plant leaves caused by a deficiency in magnesium ions, which prevents the synthesis of sufficient chlorophyll.

Tissue

A group of similar cells with a similar structure working together to perform a specific function.

Organ

A collection of different tissues working together to perform a specific physiological function.

Organ system

A group of organs working collaboratively to carry out a major body function (such as the digestive or circulatory system).

Enzyme

A biological catalyst made of protein that increases the rate of specific biochemical reactions without being consumed in the process.

Denatured

The state of an enzyme when extreme temperature or pH alters the shape of its active site, preventing the substrate from binding.

Bile

An alkaline substance produced by the liver and stored in the gall bladder that neutralises hydrochloric acid and emulsifies fats into smaller droplets.

Atherosclerosis

A condition causing coronary heart disease in which layers of fatty material build up inside the coronary arteries, narrowing them and reducing blood flow.

Stent

A metal mesh cylinder inserted into a narrowed coronary artery to keep it open, maintaining sufficient blood flow and oxygen to the heart muscle.

Statins

Prescription drugs that reduce harmful cholesterol levels in the blood, slowing down the rate of fatty deposit accumulation in arteries.

Carcinogen

A chemical substance or form of ionising radiation that causes cancer by directly damaging cellular DNA or promoting rapid cell division.

Malignant tumour

A cancerous mass of abnormal cells that invades neighbouring tissues and can spread through the bloodstream to form secondary tumours.

Transpiration

The continuous movement of water and dissolved mineral ions from plant roots, through the xylem, to the leaves where water evaporates through stomata.