Term 3 Revision

Photosynthesis

The biological process by which green plants absorb carbon dioxide gas from the atmosphere and water using sunlight energy to synthesize glucose and release oxygen gas.

Respiration

The cellular process in plants and animals that breaks down glucose to release energy, returning carbon dioxide gas back into the atmosphere.

Decomposition

The biological breakdown of dead organisms and waste products by decomposers, releasing carbon back into the soil and atmosphere.

Fossil Fuels Energy

dense carbon deposits formed underground from dead organic matter subjected to heat and pressure over millions of years (e.g., coal, crude oil, natural gas).

Combustion

The chemical reaction of burning fossil fuels, wood, or organic matter in the presence of oxygen, releasing carbon dioxide gas into the atmosphere.

Solar Energy
Renewable energy captured from sunlight using photovoltaic cells (converting photons into electrical energy) or solar heat collectors.

Wind Energy
Renewable energy harnessed from moving air currents using wind turbines that convert kinetic energy into mechanical energy and then electrical energy.

Hydroelectricity
Renewable electricity generated by flowing water from a dam/reservoir spinning the turbine blades of a generator (kinetic energy to electrical energy).

Renewable Fuel

A fuel source derived from resources that can be naturally replenished at the same rate or faster than it is consumed.

Biofuel

A renewable fuel derived from recently living organic matter (biomass) containing chemical energy that can be released via combustion.

Transverse Wave

A wave in which the particles of the medium vibrate perpendicular (at right angles) to the direction of wave travel and energy transfer.

Longitudinal Wave

A wave in which the particles of the medium vibrate parallel (push and pull) to the direction of wave travel (e.g., sound waves).

Amplitude

The maximum displacement of a wave particle from its rest (equilibrium) position, corresponding to wave energy (or sound loudness).

Crest

The highest point or peak above the equilibrium position in a transverse wave.

Trough

The lowest point below the equilibrium position in a transverse wave.

Frequency

The number of complete wave cycles that pass a given point per second, measured in Hertz (Hz); corresponds to pitch in sound.

Refraction

The bending of light (change in direction) caused by a change in its speed when passing from one optical medium into another of different density.

Transparent

A property of materials that allows almost all light to pass through clearly without significant scattering.

Opaque

A property of materials that completely absorbs or reflects light, preventing light from passing through.

Compression

A high-density region in a longitudinal wave where medium particles are bunched closely together under higher pressure.

Rarefaction

A low-density region in a longitudinal wave where medium particles are spread far apart under lower pressure.

Luminous

Describing an object or source that generates and emits its own light energy (e.g., the Sun, a light bulb, flame).

Concave Mirror

A spherical mirror curved inward that converges light rays to a focal point, capable of forming upright or inverted images.

Convex Mirror

A spherical mirror curved outward that diverges light rays, producing diminished, upright virtual images with a wide field of view.

Thermal Energy

The total internal kinetic energy of particles within a substance due to their random motion, responsible for its temperature.

Temperature

A quantitative measure of the average kinetic energy of the individual particles in a substance.

Heat

The transfer of thermal energy from a substance or object at a higher temperature to one at a lower temperature.

Conduction

The transfer of thermal energy between substances that are in direct physical contact through particle collisions without net particle movement.

Convection

The transfer of thermal energy in fluids (liquids/gases) through particle bulk movement, where warmer, less dense fluid rises and cooler, denser fluid sinks.

Radiation

The transfer of thermal energy through electromagnetic waves (infrared) that can travel through empty space without needing a material medium.

Fluid

A state of matter (liquid or gas) whose particles can move freely past one another, allowing the substance to flow and take the shape of its container.

Density

A measure of mass packed into a given volume (d = m/V); warmer fluids expand, lower their density, and rise relative to cooler, denser fluids.

Convection Current

A continuous circular flow pattern in a fluid driven by temperature and density differences during convective heat transfer.

Sound

A mechanical longitudinal wave caused by vibrating objects that transfers energy through a medium without net particle transport.

Vibration

A rapid back-and-forth oscillating motion about an equilibrium position, serving as the source of all sound waves.

Pitch

The perceptual quality of a sound determined by the wave frequency (higher frequency produces higher pitch).

Medium

The physical matter (solid, liquid, or gas) through which a mechanical wave (like sound) travels via particle interactions.

Echo

The reflection of a sound wave bouncing off a hard surface back to the listener after a delay.

Atmosphere

The layer of gases retained by Earth's gravity that surrounds the planet, composed of Nitrogen, Oxygen , Argon , and trace gases.

Hydrosphere

The total mass of water found on, under, and above the surface of the Earth in liquid, solid, or gaseous states.

Lithosphere (Geosphere)

The rigid, solid outer layer of the Earth comprising the entire crust and the upper portion of the mantle.

Biosphere

The global ecological system encompassing all living organisms (animals, plants, fungi, protists, bacteria) across land, water, and air.

Troposphere

The lowest layer of Earth's atmosphere closest to the surface containing most of the atmospheric mass, water vapor, and weather systems.

Stratosphere

The second layer of Earth's atmosphere above the troposphere, extending up to ~50 km, housing the protective ozone layer

Mesosphere

The third layer of Earth's atmosphere (~50 to 85 km) above the stratosphere, where most meteors burn up upon entry.

Thermosphere

The high-temperature fourth layer of the atmosphere (~85 to 600 km) where auroras occur and satellites orbit.

Exosphere

The outermost boundary of Earth's atmosphere that gradually fades into the vacuum of outer space.