Year 9 science sem 2 key terms

Biosphere

Part of Earth’s surface, waters, and atmosphere where living things are found

Atmosphere

The layer of gases surrounding the Earth

Hydrosphere

All waters on or over Earth

Lithosphere

Earth's rigid, rocky outer layer

Carbon cycle

The movement of carbon between Earth's spheres

Photosynthesis

Plants use carbon dioxide and sunlight to make glucose

Respiration

Living organisms release carbon dioxide into the atmosphere

Decomposition

The breakdown of dead organisms, returning carbon and other materials to the environment

Combustion

Burning fuels releases carbon dioxide into the atmosphere

Carbon sink

A natural environment that absorbs and holds more carbon than it releases over time

Fossil fuels

Coal, oil, and natural gases formed from ancient organic matter over long periods

Greenhouse gas

A gas in the atmosphere that traps heat

Natural greenhouse effect

The natural process that keeps Earth warm enough to support life

Enhanced greenhouse effect

Additional warming caused by increased greenhouse gases especially from human activities

Climate change

Long term changes in average temperatures and weather patterns

Mitigation

Action taken to reduces greenhouse gas emissions

Renewable energy

Energy from sources replenished naturally

Tectonic plate

A large, moving section of Earth’s rigid outer layer

Mantle convection

The slow movement of hot mantle material rising and cooler material sinking

Plate tectonics

The theory that Earth’s outer shell is divided into moving plates

Continental drift

The idea that continents have moved over geological time

Divergent boundary

A boundary where plates move apart and new crust can form

Convergent boundary

A boundary where plates move towards each other and can produce trenches, volcanoes or mountains

Transform boundary

A boundary where plates slide past each other and earthquakes can occur

Mid ocean ridge

An underwater mountain chain where new oceanic crust forms as plates move apart

Ring of Fire

A zone around the Pacific Ocean with many volcanoes and earthquakes

Electric current (I)

The movement of electrons throughout a period of time, measured in amps (A)

Electron

A negatively charged subatomic particle that moves through metal wires in a circuit

Conductor

A material that allows electric charge to flow easily

Insulator

A material that resists the flow of electric charge

Voltage (V)

Pushes electrons in one direction around a circuit, measured in volts (V).

Resistance (R)

How much a component opposes current, measured in ohms (Ω)

Series circuit

A circuit with one path for current

Parallel circuit

A circuit with separate branches

Ammeter

An instrument used to measure current

Voltmeter

An instrument used to measure voltage across a component

Ohm’s law for voltage

V = I x R

Ohm’s law for current

I = V ÷ R

Ohm’s law for resistance

R = V ÷ I

Independent variable

The part of an experiment that you change

Dependent variable

The part of an experiment that you measure

Controlled variable

The part of an experiment that stays the same

Crest

The highest point of a transverse wave

Trough

The lowest point of a transverse wave

Amplitude

The maximum displacement from the rest position

Wavelength

The distance between matching points on consecutive waves

Frequency

The number of complete waves passing a point each second, measured in hertz (Hz)

Electromagnetic wave

A wave that can travel through a vacuum, such as a visible light wave

Transverse wave

Particles vibrate up and down about their rest position, creating a series of crests and troughs

Wave

A carrier of energy that travels through space without the movement of matter

Longitudinal waves

Particles of the medium move back and forth parallel to the path of the energy

Compressions

Regions where particles are pushed closer together

Rarefractions

Regions where particles are spread further apart

Conduction

The transfer of thermal energy through direct contact between particles

Convection

The flow of thermal energy through a liquid or gas, caused by the movement of the liquid itself

Radiation

The transfer of energy without the need for a medium or particles

Particle model

A model that describes matter as being made of tiny particles that are always moving