Fukui Entrance Science key terms

The tendency of an object to resist any change in its state of motion. An object at rest stays at rest, and a moving object keeps moving in a straight line, until a net force acts on it.

A statement that an object continues at rest or in uniform straight-line motion unless a net external force acts on it. It defines force as the cause of changes in motion, not of motion itself.

The single force obtained by combining all forces acting on an object, taking direction into account. Only the net force determines whether the object's velocity changes and in which direction.

The relation stating that an object's acceleration equals the net force on it divided by its mass (a = F/m). Larger force gives larger acceleration; larger mass gives smaller acceleration for the same force.

The quantity of matter in an object, measured in kilograms, which resists changes in motion. Unlike weight, mass stays the same wherever the object is, including on the Moon or in orbit.

The gravitational force on an object, calculated as mass times gravitational acceleration (W = mg). On Earth g is about 9.8 N/kg, so a 1 kg object weighs about 9.8 N.

The rate at which velocity changes with time, including speeding up, slowing down, or changing direction. It is measured in metres per second squared and is caused by a net force.

Speed in a stated direction, a vector quantity measured in metres per second. Two objects with equal speed but opposite directions have different velocities, so their accelerations differ too.

Energy transferred when a force moves an object along the direction of the force, calculated as force times distance moved (W = Fd). The unit is the joule.

The capacity of a system to do work, measured in joules. It exists in forms such as kinetic, gravitational potential, elastic, thermal, chemical, and electrical, and is conserved in any change.

The energy an object possesses because of its motion, calculated as one half of mass times speed squared (KE = ½mv²). Doubling the speed multiplies kinetic energy by four.

The principle that energy is never created or destroyed, only converted between forms or transferred between objects. The total energy of an isolated system therefore stays constant.

The rate at which work is done or energy is transferred, calculated as work divided by time (P = W/t). It is measured in watts, where one watt equals one joule per second.

The relation that the current through a conductor equals the voltage across it divided by its resistance (I = V/R). It holds for metallic conductors kept at constant temperature.

The potential difference between two points in a circuit, measured in volts. It is the energy transferred per unit charge and acts as the driving force pushing current around the circuit.

The rate of flow of electric charge past a point in a circuit, measured in amperes. One ampere equals one coulomb of charge passing per second.

The opposition of a component to the flow of current, measured in ohms. For a fixed voltage, higher resistance means smaller current; it depends on material, length, and cross-sectional area.

A circuit in which components are connected one after another so the same current passes through each. The total voltage splits between components and total resistance is the sum of individual resistances.

A circuit in which components are connected across the same two points, so each receives the full source voltage. The current splits between branches and total resistance is less than any single branch resistance.

The region around a magnet or current-carrying wire where magnetic force acts on other magnets or moving charges. It is shown by field lines running from the north pole to the south pole outside a magnet.

The generation of a voltage in a conductor when the magnetic field passing through it changes. This effect underlies generators and transformers and is stronger when the change is faster or the coil has more turns.

The number of complete waves or vibrations passing a point each second, measured in hertz. It fixes the pitch of a sound and the colour of light, and does not change when a wave enters a new medium.

The distance between two consecutive corresponding points on a wave, such as crest to crest, measured in metres. It changes when a wave crosses into a medium where its speed differs.

The distance a wave crest travels per second, equal to frequency multiplied by wavelength (v = fλ). In a given medium the speed is fixed, so longer wavelength means lower frequency.

The bending of a wave as it passes from one medium into another where its speed differs. Light entering glass at an angle bends towards the normal, which is why a straw looks broken in water.

The complete reflection of light back into a denser medium when it strikes the boundary beyond the critical angle. It carries light along optical fibres and makes a water surface act like a mirror from below.

The spontaneous spreading of particles from a region of higher concentration to lower concentration because of random motion. It explains how a smell fills a room and how gases mix without stirring.

The idea that all matter is made of tiny particles in constant motion, with spacing and motion differing between solids, liquids, and gases. It explains expansion, diffusion, pressure, and changes of state.

The conversion of a substance between solid, liquid, and gas, such as melting, freezing, evaporation, and condensation. During melting or boiling, energy is used to break particle bonds, so temperature stays constant.

A separation method that boils a liquid mixture and condenses the vapour to recover a more volatile component. It is used to obtain pure water from seawater or separate ethanol from water.

A separation technique that passes a mixture through a porous barrier so that solid particles are trapped while the liquid passes through. It separates an insoluble solid from a liquid, as in muddy water.

A homogeneous mixture in which a solute is dissolved in a solvent, such as salt in water. The dissolved particles are too small to be seen or filtered out and spread evenly throughout.

A reaction in which a substance gains oxygen or loses electrons. Everyday examples include iron rusting and a fuel burning, and the oxidized substance is the one that gives up electrons.

A reaction in which a substance loses oxygen or gains electrons. It always occurs together with oxidation, as when carbon removes oxygen from copper oxide during smelting.

The reaction between an acid and a base that produces a salt and water, leaving a solution closer to neutral. It is used to treat acid spills and to relieve excess stomach acid.

A scale from 0 to 14 expressing how acidic or alkaline a solution is. Values below 7 are acidic, 7 is neutral, and above 7 is alkaline, with each unit meaning a tenfold change in hydrogen ion concentration.

An atom or group of atoms that has gained or lost electrons and so carries an electric charge. Positive ions form when electrons are lost, and negative ions form when electrons are gained, as in table salt.

An arrangement of elements in order of increasing atomic number, grouped so that elements with similar chemical properties line up in columns. Metals sit on the left, non-metals on the right.

The number of protons in the nucleus of an atom, which identifies the element and fixes its position in the periodic table. In a neutral atom it also equals the number of electrons.

The strong attraction between oppositely charged ions that holds a compound together, as between sodium and chloride ions. Such compounds form crystals and conduct electricity when melted or dissolved.

The process by which green plants use light energy to convert carbon dioxide and water into glucose and oxygen inside chloroplasts. It supplies the food and oxygen that almost all ecosystems depend on.

The controlled release of energy from glucose inside cells, using oxygen and producing carbon dioxide and water. It powers all cell activities and occurs in both plants and animals, day and night.

A protein that speeds up a specific chemical reaction in a living organism without being used up. Each enzyme works best at a particular temperature and pH, and is denatured by heat.

The breakdown of large food molecules into small soluble ones that can be absorbed into the blood. It happens mechanically by chewing and chemically by enzymes in the mouth, stomach, and small intestine.

Tiny finger-like projections lining the small intestine that greatly increase its surface area. Each contains blood vessels and a lacteal, so absorbed nutrients pass quickly into the blood or lymph.

The green pigment in chloroplasts that absorbs mainly red and blue light for photosynthesis. Because it reflects green light, leaves appear green, and light of that colour drives little photosynthesis.

Cell division that produces two genetically identical daughter cells, each with the same chromosome number as the parent. It is used for growth, repair, and asexual reproduction in body cells.

A reduction division that produces gametes with half the normal chromosome number, creating genetic variation. When two gametes fuse at fertilization, the full chromosome number is restored in the offspring.

A section of DNA on a chromosome that carries the instructions for making a particular protein, and so controls an inherited characteristic. Genes exist in alternative forms called alleles.

The relationship between two alleles of a gene in which a dominant allele shows its effect even when only one copy is present, while a recessive allele shows only when two copies are present.

Layers of sedimentary rock laid down one on top of another over long periods. In undisturbed sequences the lower layers are older, so strata record the relative order of past events.

The principle that in an undisturbed sequence of sedimentary layers, each layer is older than the one above it and younger than the one below. It allows relative dating of rock and fossils.

A fossil of a species that lived over a short time span but was widely distributed, used to identify and correlate rock layers of the same age in different places.

The boundary where two air masses of different temperature and humidity meet. Warm fronts bring gradual cloud and rain, while cold fronts bring steep clouds, heavy showers, and a sharp temperature drop.

The force per unit area exerted by the weight of air in the atmosphere, measured with a barometer. Air flows from high to low pressure, and rising low-pressure air commonly brings clouds and rain.

The changing appearance of the Moon as seen from Earth, caused by the changing angle between the Sun, Earth, and Moon. A full cycle from new moon to new moon takes about 29.5 days.

An event in which the Moon passes directly between the Sun and Earth, casting its shadow on part of Earth's surface. It can only happen at new moon, when the three bodies are exactly aligned.