Secondary 3 Science

Brain and spinal cord — they process information and give instructions.

The basic cell of the nervous system — long and specialised for carrying messages.

A change in the environment: light, sound, temperature, touch.

The part that carries out the response: a muscle or a gland.

A structure that detects stimuli — light receptors in the eye, touch receptors in the skin.

The neurone carrying messages from receptors to the central nervous system.

The neurone carrying commands from the CNS to the effector.

A bundle of many neurone fibres — like a cable.

Part of the CNS — handles thinking, memory and decisions.

An inborn, automatic, fast protective response — e.g. pulling your hand away, blinking.

The message pathway of a reflex — the brain isn't needed for the decision.

The processing centre for reflexes — messages don't have to reach the brain first.

A learned reflex, e.g. salivating at a bell (Pavlov).

A reflex present without learning — pulling away, blinking, knee-jerk.

Passes the signal from the sensory neurone straight to the motor neurone inside the spinal cord.

The inborn reflex where a tap below the knee makes the lower leg swing — a classic demonstration.

Reaches the brain only after the response — reflexes act before you feel.

A chemical messenger secreted by an endocrine gland, carried in the blood.

Released when blood glucose rises; makes the liver store glucose as glycogen, lowering blood glucose.

Released when blood glucose falls; makes the liver break down glycogen and release glucose.

When a value drifts from normal, a corrective mechanism automatically brings it back.

A gland secreting hormones straight into the blood, e.g. the pancreas.

The gland secreting insulin and glucagon — it monitors blood glucose.

Glucose stored in the liver, broken down to release glucose when needed.

The organ that stores glucose as glycogen and releases it on demand.

A disease where insulin is lacking or ineffective, leaving blood glucose chronically high.

Can be hammered or stretched without cracking — gold can be beaten into leaf.

A material that carries electricity or heat — metals conduct well.

A mixture of a metal with other elements, e.g. steel (iron + carbon), brass (copper + zinc).

Rings when struck — like bells and gongs.

The ability of a metal surface to reflect light, especially when polished.

Can be drawn into wires without breaking — copper is drawn into cables.

How well a material carries current — copper excels, so it makes wires.

How well a material carries heat — used in pans and pots.

An alloy of iron with carbon — hard and strong, used for bridges and buildings.

The ranking of metals from most to least reactive.

A more reactive metal 'kicks out' a less reactive one from its compound.

The product of a metal combining with oxygen, e.g. copper oxide (CuO).

Rarely reacts — like gold and silver.

Reaction of a metal with oxygen — the more reactive, the more easily oxidised.

An acid used to test reactivity — metals above hydrogen react with it, releasing hydrogen gas.

The reference point in the series — only metals above it react with dilute acids.

Very unreactive metals (gold, silver) occurring pure in nature.

A metal being eaten away by substances in its environment.

Specifically iron oxidising to red-brown rust (needs oxygen + water).

Coating iron with zinc to prevent rust.

Using a more reactive metal to protect the target — the reactive one corrodes first.

The flaky red-brown product of iron oxidising — it falls off and exposes fresh metal.

Keeping oxygen and water away from iron with paint, oil or plating.

Coating iron with tin (e.g. food cans); tin is less reactive, so a scratch makes the iron rust faster.

An alloy of iron with chromium and nickel — its surface layer resists rust.

Energy that naturally replenishes — solar, wind, hydro.

Fuels from ancient remains: coal, oil, natural gas.

Energy from splitting uranium atoms; low CO₂ but radioactive waste needs careful handling.

CO₂ released by burning fuels — the main driver of global warming.

Energy with finite reserves that runs out — coal, oil, gas and nuclear.

Turning sunlight into electricity with panels — zero emissions in use, but weather-dependent.

Turbines turned by wind generate power; output varies with wind speed.

Dammed water falling from a height spins turbines to generate electricity.

Energy from biological material such as wood and waste — renewable.

Energy can't be created or destroyed — only converted between forms.

The energy of a moving object.

Stored energy due to position or state — e.g. water held high.

Useful output ÷ total input × 100%. Always <100% (losses).

Energy stored in substances — batteries, food and fuels.

Energy carried by electric current — easy to transmit and convert.

The energy form given out by bulbs and screens.

The commonest loss — it warms devices up, like a torch heating in your hand.

Energy given out as noise by motors and fans — usually a loss.

Makes its own food by photosynthesis — grass, trees.

Eats other organisms: primary (herbivore), secondary/tertiary (carnivore).

Breaks down dead matter and waste, returning nutrients to the soil — bacteria, fungi.

Many interlinked food chains forming a network.

A community of organisms plus their environment, living and non-living.

A sequence of who eats whom, showing the flow of energy.

A plant-eating animal — the primary consumer, e.g. a rabbit.

An animal-eating consumer — e.g. eagles and snakes.

Energy per trophic level — widest at producers, with ~10% passing up each step.

The movement of carbon between living things, the atmosphere, oceans and rocks.

Organisms break down nutrients for energy, releasing CO₂.

Burning fuels (coal, oil) to release energy — and CO₂.

Atmospheric gases (CO₂, methane) trap heat. When excessive, it becomes global warming.

Plants absorb CO₂ and water to make food and release oxygen — the carbon cycle's main uptake.

Where carbon is held: the atmosphere, organisms, oceans and underground fossil fuels.

Clearing forests — less CO₂ absorbed, upsetting the carbon balance.

The level of CO₂ in the air — rising levels strengthen the greenhouse effect.

Emissions matched by removals — net zero; Hong Kong targets this by 2050.

The process of producing offspring.

The male organ producing sperm.

The female organ producing eggs.

The male sex cell.

The female sex cell.

The stage of sexual maturation.

The monthly shedding of the uterus lining.

The joining of sperm and egg.

About 280 days of development in the uterus.