Year 9 Comprehensive Science Study Guide: Earth Systems, Heat and Energy, Waves, Optics, and Electricity

Thermal energy

The total kinetic energy of all moving particles within an object or substance.

Temperature

The measure of the average kinetic energy of the individual particles in a substance, typically measured in degrees Celsius (C∘).

Heat

The transfer or flow of thermal energy from an object at a higher temperature to an object at a lower temperature.

Conduction

The transfer of thermal energy through a substance by direct contact and collision between particles, occurring most effectively in solids.

Convection

The transfer of thermal energy through liquids or gases caused by bulk movement of particles, where warmer, less dense fluid rises and cooler, denser fluid sinks.

Radiation

The transfer of thermal energy via electromagnetic waves, such as infrared radiation, which can travel through a vacuum without needing particles.

Law of Conservation of Energy

Energy cannot be created nor destroyed, only transferred from one object to another or transformed into different forms.

Energy efficiency

Efficiency (%)=(total input energy/useful output energy​)×100.

Atmosphere

The layer of gases surrounding Earth, composed primarily of nitrogen (78.084%78.084%) and oxygen (20.947%20.947%).

Biosphere

The global ecological system encompassing all living organisms on Earth and the environments in which they live.

Hydrosphere

All the water found on Earth's surface, underground, and in the air, including oceans, lakes, rivers, glaciers, and water vapour.

Geosphere

The solid, non-living parts of the Earth, including the crust, mantle, core, rocks, minerals, and landforms.

Stage 1: Photosynthesis

The process by which plants use sunlight, carbon dioxide (CO2​), and water to produce glucose and release oxygen (O2​).

Stage 2: Organic carbon

Animals consume plants with stored carbon.

Stage 3: Cellular respiration

The process by which living organisms break down glucose using oxygen (O2​) to release energy, producing carbon dioxide (CO2​) and water as byproducts.

Stage 4: Excretion, egestion, death & decomposition

Carbon enters the soil through waste (i.e. urine & faeces). When plants & animals die, bacteria & fungi break down their bodies, releasing CO2 back into the air.

Stage 5: Fossils and Fossil Fuels

Coal, oil & gas store carbon from dead animals & plants for millions of years. Compressed into fossils underground.

Stage 6: Combustion

Fossils are burned in factories, releasing carbon back into the atmosphere (also includes bushfires).

Stage 7: Limestone Formation

CO2 in atmosphere can dissolve in oceans, forming carbonic acid (forms calcium carbonate, which is component of shells)

CO2 can be released from limestone through weathering & erosion.

Natural greenhouse effect

The natural process where greenhouse gases such as carbon dioxide, water vapour, and methane trap outgoing infrared radiation, keeping Earth warm enough to support life.

Enhanced greenhouse effect

The intensification of heat trapping in Earth's atmosphere caused by excess greenhouse gases released through human activities like burning fossil fuels and deforestation.

Carbon sequestration

The natural or technological process of capturing carbon dioxide from the atmosphere and storing it in long-term sinks such as oceans, forests, soil, or underground rock formations.

Mechanical wave

A type of wave that requires a physical medium (matter) to propagate its vibrational energy, such as sound or water waves. Can be longitudinal or transverse.

Electromagnetic wave

A transverse wave consisting of oscillating electric and magnetic fields that can travel through matter or through a vacuum at the speed of light. Transverse only.

Transverse wave

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

Longitudinal wave

A wave in which the particles of the medium vibrate parallel to the direction of energy, creating compressions and rarefactions.

Wave equation

v=fλ (where vv represents wave speed in m/s, f represents frequency in Hz, and λ represents wavelength in mm.)

Law of reflection

The optical rule stating that the angle of incidence (i) is equal to the angle of reflection (r), both measured from the normal line.

Refraction

The bending of a light wave as it passes from one medium into another due to a change in its speed.

Total internal reflection

A light ray is completely reflected back into an optically denser medium when its angle of incidence exceeds the critical angle

Convex lens

A lens that is thicker in the middle than at the edges, causing parallel light rays to converge to a single focal point.

Concave lens

A lens that is thinner in the middle than at the edges, causing parallel light rays to diverge outwards.

Static electricity

An electric charge that builds up on the surface of an insulating object through friction and remains stationary until discharged.

Current electricity

The continuous movement or flow of electric charge (electrons) through a closed loop of conductive material.

Ohm's Law

V=I×R, stating that voltage (V) across a conductor is directly proportional to the current (I) flowing through it and its resistance (R).

Series circuit

An electrical circuit where components are connected one after another in a single loop, so the current remains the same throughout. The voltage is shared evenly between bulbs, changing their brightness. If one bulb breaks, the current is blocked.

Parallel circuit

An electrical circuit where components are placed on separate branches, providing the same voltage across each branch. The current is divided by the number of branches, and brightness is not affected. If one bulb breaks, the current can still flow through.

Layers of Earth’s atmosphere

Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere

Troposphere

The lowest layer of Earth's atmosphere, extending from the surface up to about 10-15 km, which contains 75% of atmospheric mass, drives weather systems, and holds the majority of greenhouse gases.

Stratosphere

The atmospheric layer located directly above the troposphere that contains the ozone layer, which absorbs harmful ultraviolet (UV) radiation from the Sun.

Lithosphere

The rigid outer shell of Earth consisting of the crust and upper mantle, broken into tectonic plates that move and interact.

Carbon sink

Any natural or technological reservoir, such as oceans, forests, or soil, that absorbs and stores more carbon dioxide from the atmosphere than it releases.

Regular reflection

The reflection of light off a smooth surface where parallel incident rays reflect in the same direction, producing a clear image.

Diffuse reflection

The scattering of light rays in many different directions caused by reflection off a rough or uneven surface, preventing the formation of a clear image.

Frequency formula

number of waves/time

Geological storage

•injected into underground rock formations

Mineral storage

C02 reacted with certain types of minerals to produce stable carbonates.

Ocean storage

•injected into Ocean where it can dissolve & be stored in the deep sea.

What are the three properties of light?

1. Light is at a universal speed, fastest

2. Light does not need a medium to travel

3. Light can be transmitted, absorbed, or reflected.

Carbon dioxide - what is responsible for maknig it

Burning fossil fuels such as coal, oil and gas. Currently 70% of Australia’s electricity is produced by burning coal.

Methane

Farming cattle (which produce methane when they digest grass) and growing rice paddies. Increased temperatures lead to melting permafrost. Permafrost is frozen soil that contains trapped methane produced from the decomposition of plants and animals.

Nitrous oxide

Using fertiliser, which increases the amount of nitrogen in the nitrogen cycle, therefore increasing the production of nitrous oxide.

Water vapour

Although water vapour is naturally abundant greenhouse gas, as the concentration of carbon dioxide, methane & nitrous oxide increases due to human activity, more heat is trapped, which contributes to increasing water vapour concentration (humidity).

Oceans (carbon sink)

The surface of the ocean acts as a sink for atmospheric CO2.

CO2 dissolves into seawater, where it reacts with water molecules to form carbonic acid (H2C03).

Scientist have estimated that it absorbs 25% of the C02 released into the atmosphere by human activities.

Colder water is more effective at dissolving & absorbing C02 than warmer water.

Forest

As trees grow, they absorb CO2 from the atmosphere through photosynthesis, using it to build biomass. Trees store CO2 in their trunks, branches, leaves & roots.

Soil

Carbon sequestration in soil occurs through the process of photosynthesis.

Plants take in C02 from the atmosphere and convert it into organic matter. When plants die, this organic matter is deposited in the soil where it can be stored.

Earth

Bottom plug

Neutral

Top right plug

Active

Top right plug

Fuse

Melts when the current through it reaches a certain value, breaking the circuit.

Circuit breaker

same function as a fuse by breaking the circuit when the current through it exceeds a certain threshold.

2 plugs

Double insulation

Earthing

Allows the electric current to flow to the ground in the case of a fault. Prevents electrocution

Firestick farming

•Land management – By strategically burning specific areas at certain times of the year, it encourages the growth of certain plant species, clear underbrush and create open spaces for hunting and gathering.

•Biodiversity – Creates a mosaic of habitats with varying stages of vegetation growth which supports a wide range of plant & animal species.

•Nutrient cycling – returning organic matter to the soil in form of ash, making it more fertile & conducive to plant growth.

•Fire management – reduces risk of large, uncontrollable fires