LGCSE Physical Science (0181) flashcards
LGCSE Physical Science (0181) · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Independent variable
- The variable the experimenter deliberately changes between trials, plotted on the x-axis of a graph, so its effect on the measured outcome can be investigated.
- Systematic error
- An error that shifts every reading in the same direction, such as a zero error or mis-calibrated instrument; repeating readings and averaging does not remove it.
- Diffusion
- The net random spreading of particles from a region of higher concentration to lower concentration, caused by particle motion; faster at higher temperatures and in gases.
- Chromatography Rf value
- Retardation factor: distance travelled by the spot divided by distance travelled by the solvent front from the same baseline; used to identify dissolved substances.
- Mass number
- The total number of protons and neutrons in the nucleus of an atom, written as a superscript before the symbol; neutrons equal mass number minus atomic number.
- Ionic bond
- The strong electrostatic attraction between oppositely charged ions formed when a metal atom transfers electrons to a non-metal atom, producing a giant lattice.
- Mole
- The amount of substance containing 6.02 × 10²³ particles; its mass in grams equals the molar mass, and one mole of gas occupies about 24 dm³ at room temperature.
- Limiting reactant
- The reactant that is completely used up first in a reaction; its amount determines the maximum mass of product that can be formed.
- Neutralisation
- The reaction between an acid and a base producing a salt and water only; hydrogen ions from the acid combine with hydroxide ions from the alkali.
- Activation energy
- The minimum energy colliding particles need for a reaction to occur; catalysts lower it by providing an alternative reaction pathway.
- Newton's second law
- The resultant force on an object equals its mass multiplied by its acceleration (F = ma); force is measured in newtons when mass is in kilograms.
- Terminal velocity
- The constant velocity reached by a falling object when the upward drag force equals its weight, so the resultant force and acceleration are zero.
- Kinetic energy
- The energy an object has because of its motion, calculated as one half times mass times velocity squared (KE = ½mv²), measured in joules.
- Efficiency
- The ratio of useful energy output to total energy input, usually expressed as a percentage; energy not used is dissipated, often as heat.
- Refractive index
- The ratio of light speed in a vacuum to its speed in a medium; also equal to sine of incidence angle divided by sine of refraction angle.
- Total internal reflection
- Complete reflection of light inside a denser medium when the angle of incidence exceeds the critical angle, used in optical fibres and prisms.
- Ohm's law
- The current through a conductor is directly proportional to the potential difference across it, provided its temperature stays constant (V = IR).
- Parallel circuit rule
- Components connected across the same potential difference; the total current is the sum of branch currents and total resistance is less than the smallest branch resistance.
- Specific heat capacity
- The energy needed to raise the temperature of one kilogram of a substance by one degree Celsius, measured in joules per kilogram per degree.
- Specific latent heat
- The energy needed to change the state of one kilogram of a substance at constant temperature, without any change in its temperature.
- Greenhouse effect
- Atmospheric gases absorb infrared radiation emitted by Earth's surface and re-emit it in all directions, keeping the surface warmer than it would otherwise be.
- Igneous rock
- Rock formed when molten magma or lava cools and solidifies; slow cooling underground gives large crystals, rapid cooling at the surface gives small ones.
- Electrolysis
- The breakdown of an ionic compound, molten or in solution, by passing a direct electric current through it, producing products at the electrodes.
- Exothermic reaction
- A reaction that transfers energy to the surroundings, usually shown by a rise in temperature; the products have less chemical energy than the reactants.
- Fair test
- An investigation in which only the independent variable is changed while all other relevant variables are kept constant, so the effect measured is attributable.
- Filtration
- A separation technique that uses a filter paper to trap an insoluble solid while the liquid passes through as the filtrate.
- Isotopes
- Atoms of the same element with the same number of protons but different numbers of neutrons, so they have different mass numbers but identical chemical properties.
- Percentage yield
- The actual mass of product obtained expressed as a percentage of the theoretical maximum mass calculated from the balanced equation.
- Collision theory
- Reaction rate depends on how often particles collide with at least the activation energy; concentration, temperature, surface area and catalysts affect this.
- Moment of a force
- The turning effect of a force, calculated as force multiplied by the perpendicular distance from the pivot; measured in newton metres.
- Power
- The rate at which energy is transferred or work is done, calculated as energy divided by time and measured in watts, where one watt is one joule per second.
- Converging lens
- A lens thicker in the middle that brings parallel rays of light to a focus; its power in dioptres equals one divided by focal length in metres.
- Electrical resistance
- The opposition to current flow in a component, equal to potential difference divided by current (R = V/I) and measured in ohms.