Glossary
Acceleration
How quickly speed or direction changes.
The rate of change of velocity, equal to resultant force divided by mass.
A 60 N resultant force on 20 kg gives 3 m/s squared.
Used in: Newton's Three LawsAdaptation
A feature that helps an organism survive where it lives.
An inherited characteristic that increases fitness in a particular environment.
Thick fur is an adaptation to cold climates.
Used in: Variation and Natural SelectionAnaerobic respiration
Releasing energy from glucose without oxygen.
Respiration in the absence of oxygen, producing lactic acid in animal cells.
Sprinters rely on anaerobic respiration in the final seconds.
Used in: Cellular Respiration and Energy ReleaseAnion
A negative ion - it has gained electrons.
An ion with a net negative charge, formed by the gain of one or more electrons.
Cl-, O2-
Used in: Understanding IonsAtomic number
The number of protons in an atom - it tells you which element it is.
The number of protons in the nucleus of an atom, defining the element.
Carbon has atomic number 6
Used in: Inside the AtomAverage speed
Total distance divided by total time.
The mean rate of change of distance over a whole journey.
A 100 m sprint in 12.5 s gives an average speed of 8 m/s.
Used in: Speed, Distance and TimeCation
A positive ion - it has lost electrons.
An ion with a net positive charge, formed by the loss of one or more electrons.
Mg2+, K+
Used in: Understanding IonsCell
The smallest living building block of an organism.
The basic structural and functional unit of all living organisms.
A single amoeba is one cell that carries out all life processes.
Used in: Cells: The Basic Unit of LifeChloroplast
The green organelle where a plant makes food.
A plastid containing chlorophyll where photosynthesis occurs.
Leaf cells are packed with chloroplasts.
Used in: Inside Plant and Animal CellsChromosome
A tightly coiled thread of DNA in the nucleus.
A DNA molecule packaged with proteins, carrying many genes.
Humans have 46 chromosomes in most body cells.
Used in: DNA, Genes and ChromosomesClosed system
A container where nothing can get in or out.
A system that exchanges energy but not matter with its surroundings.
A sealed flask during a reaction
Used in: Conservation of MassCollision theory
The idea that particles must bump into each other hard enough to react.
A model stating that reaction rate depends on the frequency and energy of collisions relative to the activation energy.
Explaining why heating speeds up reactions
Used in: What Affects Reaction RatesCrumple zone
A part of a car designed to fold in a crash.
A structure that extends collision time, reducing the force for a given momentum change.
Crumple zones lower the force felt by passengers.
Used in: Momentum and CollisionsCurrent
The flow of electric charge around a circuit.
The rate of flow of electric charge, measured in amperes.
An ammeter in series reads a current of 0.3 A.
Used in: Current, Voltage and ResistanceDissipation
Energy spreading out and becoming less useful.
The transfer of energy to the surroundings, usually by heating.
A phone becomes warm as energy is dissipated.
Used in: Energy Stores and TransfersDominant allele
The version of a gene that shows even if only one copy is present.
An allele expressed in the phenotype in both homozygous and heterozygous states.
B for brown eyes is dominant over b for blue.
Used in: Punnett Squares and ProbabilityElectrolyte
A substance that lets a solution carry electricity because it releases ions.
A compound that dissociates into free ions in solution or when molten, allowing electrical conduction.
Sodium chloride solution
Used in: Understanding IonsElectromagnet
A magnet made by passing current through a coil.
A solenoid, usually with a ferromagnetic core, magnetised by an electric current.
A scrapyard crane uses an electromagnet to lift and drop cars.
Used in: Magnetism and ElectromagnetsElectrostatic attraction
The pull between opposite charges.
The force of attraction between oppositely charged particles described by Coulomb's law.
Na+ attracting Cl- in a lattice
Used in: Understanding IonsEnergy store
Where energy is held before it moves.
A description of energy associated with a system, such as kinetic or chemical.
A charged battery holds a chemical energy store.
Used in: Energy Stores and TransfersEnzyme
A protein that speeds up a reaction in your body.
A biological catalyst that lowers the activation energy of a specific reaction.
Amylase breaks starch into sugars in the mouth.
Used in: Digestion and Nutrient TransportForce
A push or a pull on an object.
An interaction that changes an object's motion or shape, measured in newtons.
Friction is a force that slows a sliding book.
Used in: Describing ForcesFossil
Preserved remains or traces of an ancient organism.
Mineralised or otherwise preserved evidence of past life in rock.
Trilobite fossils show life in ancient seas.
Used in: Evidence for EvolutionFrequency
How many waves pass each second.
The number of complete oscillations per second, measured in hertz.
A guitar string vibrating 440 times per second has a frequency of 440 Hz.
Used in: Properties of WavesGene
A section of DNA with instructions for one feature.
A length of DNA that codes for a specific protein.
A gene codes for the pigment in your iris.
Used in: DNA, Genes and ChromosomesGravitational potential energy
The energy stored by lifting something up.
Energy stored due to an object's position in a gravitational field, m x g x h.
Lifting a 1.2 kg book 1.5 m stores about 17.6 J.
Used in: Kinetic and Gravitational Potential EnergyHeterozygous
Having two different versions of a gene.
Possessing two different alleles of a given gene.
A Bb individual is heterozygous and carries the recessive allele.
Used in: Punnett Squares and ProbabilityHomologous structures
Body parts with the same basic plan but different uses.
Structures shared by different species due to common ancestry.
A whale flipper and a human arm share the same bone pattern.
Used in: Evidence for EvolutionInertia
The tendency of an object to keep doing what it is doing.
The resistance of an object to a change in its state of motion, related to its mass.
Passengers lurch forwards when a bus brakes suddenly.
Used in: Newton's Three LawsIon
An atom that has gained or lost electrons, so it now has an electrical charge.
A charged species formed when the number of electrons no longer equals the number of protons.
Na+ in table salt solution
Used in: Understanding IonsIonic lattice
A regular 3D arrangement of alternating positive and negative ions.
A giant ionic structure in which each ion is surrounded by ions of opposite charge in a repeating pattern.
Sodium chloride crystal
Used in: Ionic BondingKinetic energy
The energy an object has because it is moving.
Energy of motion, equal to half the mass times the velocity squared.
A 0.45 kg ball at 20 m/s has 90 J of kinetic energy.
Used in: Kinetic and Gravitational Potential EnergyMagnetic field
The region where a magnet can exert a force.
A region in which a magnetic material or moving charge experiences a force.
Iron filings reveal the field around a bar magnet.
Used in: Magnetism and ElectromagnetsMomentum
Mass in motion: how hard something is to stop.
The product of an object's mass and velocity, measured in kg m/s.
A 1200 kg car at 15 m/s has 18000 kg m/s of momentum.
Used in: Momentum and CollisionsNatural selection
Better suited individuals survive and pass on their traits.
The process by which heritable traits that improve survival and reproduction become more common in a population.
Dark moths survived better on soot-covered bark.
Used in: Variation and Natural SelectionNormal
An imaginary line at right angles to a surface.
A construction line perpendicular to the surface at the point of incidence.
Angles of incidence and reflection are measured from the normal.
Used in: Light: Reflection and RefractionOrgan system
A group of organs that work together on one big job.
A set of organs functioning together to perform a major physiological role.
The circulatory system includes the heart, blood and vessels.
Used in: Body Systems Working TogetherOrganelle
A tiny structure inside a cell with a specific job.
A specialised subunit within a cell that performs a particular function.
Mitochondria are organelles that release energy.
Used in: Inside Plant and Animal CellsParticle model
The idea that all matter is made of tiny moving particles.
A model describing matter as particles whose arrangement and motion explain macroscopic properties.
Explaining why gases fill a room
Used in: Particles and States of MatterPhotosynthesis
How plants use light to make their own food.
The process converting light energy into chemical energy stored in glucose using carbon dioxide and water.
A leaf in sunlight releases oxygen as it photosynthesises.
Used in: Photosynthesis and Food ProductionProducer
A living thing that makes its own food.
An autotrophic organism that synthesises organic compounds from inorganic sources.
Grass is the producer at the start of many food chains.
Used in: Photosynthesis and Food ProductionRefraction
Light bending as it enters a new material.
The change in direction of a wave caused by a change in its speed at a boundary.
A straw appears bent where it enters water.
Used in: Light: Reflection and RefractionResistance
How much a component slows the flow of charge.
The ratio of potential difference to current, measured in ohms.
A 4 ohm resistor needs 12 V for a 3 A current.
Used in: Current, Voltage and ResistanceRespiration
How cells release energy from food.
The controlled breakdown of glucose in cells to release energy for cellular work.
Muscle cells respire faster during exercise.
Used in: Cellular Respiration and Energy ReleaseResultant force
The single force left over after adding all forces.
The vector sum of all forces acting on an object.
A 10 N push against 4 N of friction gives a 6 N resultant.
Used in: Describing ForcesSpeed
How far something travels each second.
The rate of change of distance with time.
A cyclist covering 6 m each second travels at 6 m/s.
Used in: Speed, Distance and TimeTissue
A group of similar cells doing the same job.
A group of similar cells with a common origin and function.
Muscle tissue contracts to produce movement.
Used in: Body Systems Working TogetherUnicellular
Made of only one cell.
An organism consisting of a single cell that performs all life functions.
Yeast used in bread making is unicellular.
Used in: Cells: The Basic Unit of LifeVilli
Tiny finger-like folds that soak up nutrients.
Projections of the small intestine wall that increase surface area for absorption.
Villi give the small intestine a huge absorbing surface.
Used in: Digestion and Nutrient TransportWavelength
The distance between one wave peak and the next.
The distance between two successive corresponding points on a wave.
A 340 m/s sound at 250 Hz has a wavelength of 1.36 m.
Used in: Properties of Waves