Half the battle is knowing what to call it.
A working glossary for the terms that show up in the lab. Search a word, jump to a letter and read the version that connects to a model you can actually see.
46terms
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These definitions are deliberately short enough to use mid-session. Expand a term for the longer explanation and the ideas it connects to.
Science glossary
46 terms / four disciplines
46 terms
AcidChemistryA substance that donates hydrogen ions in solution.+
A strong acid releases almost all of its hydrogen ions in water. A weak acid releases only some, which is why two acids at the same concentration can have very different pH values.
Related / Base / pH / Neutralisation
Action potentialMedicineA rapid electrical change that travels along a neuron.+
Sodium ions rush into the cell and reverse the voltage across its membrane. The signal then travels down the axon before the cell restores its resting voltage.
Related / Neuron / Synapse
Activation energyChemistryThe minimum energy a reaction needs before it can proceed.+
Molecules need enough energy to break the bonds that stand in the way. A catalyst lowers this barrier without changing the overall energy released by the reaction.
Related / Catalyst / Reaction rate / Enzyme
AlleleBiologyOne version of a gene.+
A person inherits two alleles for most genes, one from each parent. Which allele is expressed depends on whether it is dominant or recessive.
Related / Gene / DNA
AtomChemistryThe smallest unit of an element that keeps its identity.+
An atom contains protons and neutrons in a dense nucleus, with electrons around it. The number of protons determines which element it is.
Related / Electron / Valence electron / Molecule
BaseChemistryA substance that accepts hydrogen ions or releases hydroxide ions.+
Strong bases such as sodium hydroxide release hydroxide ions in water. Bases neutralise acids and produce a salt and water together with them.
Related / Acid / pH / Neutralisation
Base pairBiologyTwo nucleotides that pair across the DNA ladder.+
Adenine pairs with thymine, and guanine pairs with cytosine. This matching rule allows DNA to be copied accurately.
Related / DNA / Gene
CatalystChemistryA substance that speeds a reaction without being used up.+
A catalyst offers a lower energy route for the reaction. It changes the rate, not the final amount of product at equilibrium.
Related / Activation energy / Reaction rate / Enzyme
Cell membraneBiologyThe selective boundary around a cell.+
A phospholipid bilayer controls what enters and leaves the cell. Embedded proteins act as channels, pumps and receptors.
Related / Diffusion / Osmosis
CircuitPhysicsA closed path through which charge can flow.+
A complete circuit needs a source of potential difference and a conducting path. Break the path and the current stops.
Related / Current / Potential difference / Resistance
ConcentrationChemistryThe amount of a solute in a given volume of solution.+
Concentration is often measured in moles per cubic decimetre. Doubling the concentration puts twice as many reacting particles in the same space.
Related / Mole / Reaction rate / Titration
Covalent bondChemistryA bond formed when atoms share a pair of electrons.+
Shared electrons hold the nuclei together. A covalent bond can be polar or nonpolar depending on how evenly the electrons are shared.
Related / Molecule / Hydrogen bond / Valence electron
CurrentPhysicsThe rate of charge flow through a circuit.+
Current is measured in amperes. One ampere is one coulomb of charge passing a point each second.
Related / Circuit / Potential difference / Resistance
DiffusionBiologyThe movement of particles from high to low concentration.+
Particles spread out because of their random motion. Diffusion needs no energy input from the cell and continues until the concentration is even.
Related / Osmosis / Cell membrane / Concentration
DNABiologyThe molecule that carries genetic instructions.+
DNA is a double helix of nucleotides. The sequence of bases encodes the proteins a cell can build.
Related / Gene / Base pair / Allele
ElectronChemistryA negatively charged particle found around an atom.+
Electrons occupy shells or orbitals around the nucleus. The electrons in the outer shell are the ones most involved in bonding.
Related / Atom / Valence electron / Ionic bond
EndothermicChemistryA reaction that takes in energy from its surroundings.+
The products contain more energy than the reactants. The surroundings cool as the reaction absorbs heat.
Related / Exothermic / Activation energy
EnzymeBiologyA protein that speeds up a biological reaction.+
Enzymes are specific to their substrates. Temperature and pH can change the shape of the active site and slow the reaction.
Related / Catalyst / Activation energy
Equivalence pointChemistryThe point where acid and base have reacted in exact amounts.+
At equivalence, the moles of acid equal the moles of base for the balanced equation. For a strong acid and strong base, the pH is 7.
Related / Titration / Indicator / Neutralisation
ExothermicChemistryA reaction that releases energy to its surroundings.+
The products contain less energy than the reactants. The energy difference is released as heat, light or sound.
Related / Endothermic / Activation energy
ForcePhysicsA push or pull that can change an object's motion.+
Force is measured in newtons. A net force changes velocity, while balanced forces leave motion unchanged.
Related / Newton's second law / Friction
FrictionPhysicsA force that resists motion between surfaces.+
Friction converts kinetic energy into heat. It can be reduced with lubrication or shaped surfaces, but it cannot be removed completely in everyday conditions.
Related / Force / Kinetic energy
GeneBiologyA section of DNA that codes for a protein or trait.+
Genes are inherited and can exist in different versions called alleles. Gene expression depends on the cell type and its environment.
Related / DNA / Allele
GlucoseBiologyA simple sugar used as fuel and as a building block.+
Photosynthesis produces glucose from carbon dioxide and water. Cells break it down during respiration to release usable energy.
Related / Photosynthesis / Enzyme
HomeostasisMedicineThe body keeping its internal conditions stable.+
Temperature, blood glucose and water balance are held within narrow ranges. Negative feedback loops detect a change and act to reverse it.
Related / Neuron / Hormone
HormoneMedicineA chemical messenger carried in the blood.+
Hormones act on specific target cells with matching receptors. Small amounts can produce large, slow changes across the body.
Related / Homeostasis / Enzyme
Hydrogen bondChemistryA weak attraction between polar molecules.+
Hydrogen bonds form when hydrogen is attached to a highly electronegative atom. They are individually weak but collectively shape water, proteins and DNA.
Related / Covalent bond / Molecule
IndicatorChemistryA substance that changes colour with pH.+
Phenolphthalein is colourless below pH 8.2 and pink above it. An indicator marks the end point, which is close to equivalence for a strong acid and strong base.
Related / Titration / pH / Equivalence point
Ionic bondChemistryAn attraction between oppositely charged ions.+
Electrons are transferred rather than shared. The resulting ions pack into a lattice held together by electrostatic attraction.
Related / Electron / Atom
Kinetic energyPhysicsThe energy an object has because it is moving.+
Kinetic energy depends on mass and the square of speed. Doubling speed gives four times the kinetic energy.
Related / Force / Friction
MoleChemistryAn amount containing 6.022 times 10 to the 23 particles.+
The mole lets chemists count particles by weighing them. One mole of a substance has a mass in grams equal to its relative formula mass.
Related / Concentration / Titration
MoleculeChemistryA group of atoms held together by covalent bonds.+
A molecule can contain one element or several. Its shape affects properties such as polarity, boiling point and how it interacts with other molecules.
Related / Covalent bond / Atom
NeuronMedicineA cell that carries electrical messages through the body.+
Dendrites receive signals, the cell body integrates them and the axon carries the result toward a synapse. Myelin insulation speeds the signal up.
Related / Action potential / Synapse
NeutralisationChemistryThe reaction between an acid and a base.+
An acid and a base react to form a salt and water. The pH moves toward neutral if the acid and base are strong.
Related / Acid / Base / Titration
Newton's second lawPhysicsForce equals mass times acceleration.+
For a fixed mass, a larger force produces a larger acceleration. Doubling the mass halves the acceleration for the same force.
Related / Force / Kinetic energy
OsmosisBiologyThe movement of water across a partially permeable membrane.+
Water moves from a region of higher water potential to lower water potential. Plant cells stay firm when water enters and can lose shape when it leaves.
Related / Diffusion / Cell membrane
pHChemistryA scale from 0 to 14 that measures hydrogen ion concentration.+
pH is negative log base ten of hydrogen ion concentration. Each whole step is a tenfold change in hydrogen ion concentration.
Related / Acid / Base / Indicator
PhotosynthesisBiologyThe process plants use to turn light into chemical energy.+
Carbon dioxide and water become glucose and oxygen. Chlorophyll captures light, and the products move through the plant for growth and storage.
Related / Glucose / Cell membrane
Potential differencePhysicsThe energy transferred per unit of charge.+
Potential difference is measured in volts. A 12 volt supply transfers 12 joules for every coulomb of charge that passes through it.
Related / Circuit / Current / Resistance
Reaction rateChemistryHow quickly a reaction converts reactants into products.+
Rate changes with concentration, temperature, surface area and catalysts. Faster particles collide more often and with more energy.
Related / Activation energy / Catalyst / Concentration
ResistancePhysicsHow strongly a component opposes current.+
Resistance is measured in ohms. For a fixed potential difference, a higher resistance means a smaller current.
Related / Current / Potential difference / Circuit
SynapseMedicineThe junction where a neuron passes a signal on.+
An electrical signal triggers the release of neurotransmitters into the gap. The next cell responds only if it has the matching receptors.
Related / Neuron / Action potential
TitrationChemistryA method for finding the concentration of a solution.+
A solution of known concentration is added until the reaction is complete. The volume used and the balanced equation reveal the unknown concentration.
Related / Equivalence point / Indicator / Mole
Valence electronChemistryAn electron in the outermost shell of an atom.+
Valence electrons are the ones most likely to be shared, lost or gained in bonding. Their number determines an element's group chemistry.
Related / Electron / Covalent bond / Ionic bond
WavePhysicsA disturbance that transfers energy from place to place.+
A wave has wavelength, frequency and amplitude. The wave carries energy without carrying matter along with it.
Related / Wavelength / Current
WavelengthPhysicsThe distance between two matching points on a wave.+
Wavelength is measured in metres and is inversely related to frequency. Shorter wavelengths carry more energy for electromagnetic waves.
Related / Wave
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