Science Notes 3.1–3.3: Heat, Sound & Light

Vocabulary flashcards covering key terms and definitions from the lecture notes on heat, sound, and light.

Law of Conservation of Energy

Principle stating that energy is neither created nor destroyed, only transformed between forms.

Particle Model of Matter

Theory that all matter is made of constantly moving particles whose arrangement and motion determine the state of matter.

Solid (Particle Arrangement)

State in which particles are tightly packed and vibrate in place, giving a fixed shape and volume.

Liquid (Particle Arrangement)

State where closely packed particles slide past one another, allowing a fixed volume but variable shape.

Gas (Particle Arrangement)

State with widely spaced particles moving freely in straight lines until collisions occur, giving no fixed shape or volume.

Heat

Total kinetic energy of all particles in a substance; depends on temperature and mass.

Temperature

Measure of the average kinetic energy of particles in a substance.

Absolute Zero

Theoretical temperature (0 K = −273.15 °C) at which particles have zero kinetic energy and motion stops.

Kelvin Scale

Temperature scale beginning at absolute zero; convert from Celsius by adding 273.15.

Thermometer

Device that measures temperature using expansion and contraction of a liquid such as mercury or alcohol.

Thermal Expansion

Increase in volume and decrease in density of a substance as its temperature rises and particles move faster.

Thermal Contraction

Decrease in volume and increase in density as temperature falls and particle motion slows.

Melting

Change of state from solid to liquid caused by added heat and increased particle vibration.

Boiling / Evaporation

Change of state from liquid to gas when particles gain enough energy to overcome attractive forces.

Conduction

Heat transfer through direct contact where vibrating particles pass energy to neighbours.

Convection

Heat transfer in fluids via movement of warmer, less-dense regions rising and cooler, denser regions sinking.

Convection Current

Circular flow pattern created by rising warm fluid and sinking cool fluid during convection.

Radiation (Heat)

Transfer of thermal energy by infrared electromagnetic waves without requiring a medium.

Conductor (Heat)

Material that transfers heat efficiently, e.g., metals or glass.

Insulator (Heat)

Material that resists heat flow, trapping thermal energy, e.g., air, wool, polystyrene.

Sound

Form of energy produced by vibrating objects that create longitudinal pressure waves in a medium.

Transverse Wave

Wave in which particle motion is perpendicular to wave direction; examples include light and water waves.

Longitudinal Wave

Wave where particle motion is parallel to wave direction; sound waves are this type.

Compression (Sound)

Region in a longitudinal wave where particles are crowded together and pressure is higher.

Rarefaction

Region in a longitudinal wave where particles are spread apart and pressure is lower.

Wavelength

Distance between successive compressions or rarefactions (or crests/troughs) in a wave.

Amplitude

Maximum displacement of particles from rest position; corresponds to loudness or brightness.

Frequency

Number of complete waves passing a point per second, measured in hertz (Hz); determines pitch or colour.

Period (Wave)

Time taken for one complete wavelength to pass a point.

Speed of Sound

Rate at which sound travels; fastest in solids, slower in liquids, slowest in gases, and higher in warm materials.

Light

Electromagnetic radiation that travels in transverse waves at about 300,000 km/s.

Electromagnetic Radiation

Energy that travels as oscillating electric and magnetic fields, including radio waves, light, X-rays, etc.

Transparent Material

Substance that allows all light to pass through with little scattering, e.g., clear glass.

Translucent Material

Substance that lets some light through but scatters it, producing a blurred image, e.g., frosted glass.

Opaque Material

Substance that blocks light entirely, preventing transmission, e.g., wood.

Luminous Object

Object that produces its own light, such as the Sun or a light bulb.

Illuminated Object

Object that is visible because it reflects light from another source, e.g., the Moon.

Dispersion

Separation of white light into its component colours when passing through a prism.

Electromagnetic Spectrum

Continuous range of electromagnetic waves ordered by wavelength/frequency, from radio to gamma rays.

Reflection (Light)

Bouncing of light off a surface.

Law of Reflection

Principle stating that the angle of incidence equals the angle of reflection relative to the normal.

Regular Reflection

Reflection from a smooth surface that produces a clear image.

Diffuse Reflection

Scattered reflection from a rough surface, preventing image formation.

Plane Mirror

Flat mirror producing an upright, laterally inverted, same-size virtual image behind the mirror.

Concave Mirror

Inward-curved mirror that converges light to a focal point; can form real or virtual images depending on object distance.

Convex Mirror

Outward-curved mirror that diverges light and always forms virtual, upright, diminished images.

Refraction

Bending of light as it passes between media of different densities due to a change in speed.

Refractive Index

Measure of how much a medium slows light; higher index means slower light and bending toward the normal.

Convex (Converging) Lens

Outward-curved lens that focuses parallel light rays to a point; used in eyes, cameras, magnifiers.

Concave (Diverging) Lens

Inward-curved lens that spreads light rays outward; used to correct short-sightedness.

Colour Filters

Transparent materials that transmit only selected wavelengths and absorb the rest.

Seeing Colour

Phenomenon where objects appear coloured because they reflect certain wavelengths and absorb others.