Year 9 Science - Comprehensive Exam Vocabulary Flashcards

Comprehensive vocabulary flashcards covering the core topics of the Year 9 Science course: Energy, Disease, Materials, Environmental Sustainability, and Working Scientifically.

Law of conservation of energy

The scientific principle stating that energy cannot be created or destroyed, only transferred or transformed, meaning total energy in a closed system remains constant.

Energy transfer

The movement of energy from one object or location to another without changing its form.

Energy transformation

The change of energy from one form into another.

Energy efficiency

The percentage of input energy that is transferred into useful output energy, calculated as $\text{Efficiency (\%)} = \left(\frac{\text{useful energy output}}{\text{total energy input}}\right) \times 100$.

Renewable energy sources

Energy sources that are naturally replenished, such as solar, wind, hydroelectric, and geothermal energy.

Non-renewable energy sources

Finite energy sources that take millions of years to form, such as coal, oil, natural gas, and uranium.

Complete circuit

An electrical path requiring a power source, conducting wires, and a load (such as a lamp) along a closed conducting path.

Voltage

The electrical potential difference between two points, measured in volts ($V$).

Electric current

The rate of flow of electric charge, measured in amperes ($A$).

Resistance

The opposition to the flow of electric current, measured in ohms ($\Omega$).

Ohm's law

The relationship stating that voltage equals current multiplied by resistance: $V = IR$.

Homeostasis

The maintenance of stable internal conditions within an organism despite external changes, ensuring conditions remain suitable for enzymes, cells, and organs to function properly.

Stimulus

A change in the internal or external environment that causes an organism to produce a response.

Feedback loop

A biological process that detects changes and triggers responses to regulate internal conditions.

Negative feedback

A regulatory mechanism that reverses a detected change to bring internal conditions back towards their normal range.

Pathogen

A biological agent that causes infectious disease; the four primary types are bacteria, viruses, fungi, and parasites.

Infectious disease

A disease caused by a pathogen that can be transmitted directly or indirectly between organisms.

Non-infectious disease

A disease not caused by a transmissible pathogen that cannot spread between people, resulting from genetic factors, lifestyle choices, nutritional deficiencies, or environmental exposures.

Epidemic

A sudden rise in disease cases above what is normally expected within a particular population or area.

Endemic disease

A disease that is consistently present at an expected level within a particular population or geographical region.

Pandemic

An epidemic that spreads across multiple countries or continents, affecting a large number of people.

Antibodies

Proteins produced by certain white blood cells that bind specifically to target antigens on pathogens.

Vaccination

The introduction of a vaccine that safely exposes the immune system to an antigen to stimulate an immune response and the formation of memory cells.

Herd immunity

A form of indirect protection occurring when enough people in a population are immune that pathogen transmission becomes less likely, protecting vulnerable individuals.

Incidence

The number of newly diagnosed cases of a disease occurring within a population over a specific period of time.

Prevalence

The total number of existing disease cases in a population at a particular point in time or over a defined period.

Finite resources

Non-renewable natural substances and minerals that exist in limited amounts and form far more slowly than the rate at which they are extracted.

Valency

The combining capacity of an atom, determined by the number of electrons it needs to gain, lose, or share to attain chemical stability.

Noble gas configuration

A stable electron arrangement characterised by having a completely full outer electron shell.

Ionic bond

The electrostatic attraction formed between oppositely charged ions following the transfer of electrons.

Covalent bond

A chemical bond formed when two non-metal atoms share one or more pairs of electrons.

Metallic bond

The electrostatic attraction between fixed positive metal ions and a surrounding sea of delocalised electrons.

Cation

A positively charged ion formed when a neutral atom loses one or more electrons.

Anion

A negatively charged ion formed when a neutral atom gains one or more electrons.

Organic compound

A carbon-based chemical compound that typically contains carbon–hydrogen bonds.

Inorganic compound

A chemical compound not generally classified as organic, such as sodium chloride ($NaCl$) or carbon dioxide ($CO_2$).

Hydrocarbon

A compound containing only hydrogen and carbon atoms.

Crude oil

A naturally occurring, complex mixture composed predominantly of hydrocarbons formed over millions of years from ancient organic matter.

Fractional distillation

A separation method used to separate the components of crude oil into distinct fractions based on differences in their boiling points.

Alkane

A saturated hydrocarbon containing only single covalent carbon–carbon bonds, following the general formula $C_nH_{2n+2}$.

IUPAC nomenclature

A universally accepted systematic method for naming chemical compounds based on their structural characteristics.

Complete combustion

The reaction of burning a hydrocarbon in an abundant supply of oxygen, producing carbon dioxide ($CO_2$), water ($H_2O$), and releasing maximum energy.

Incomplete combustion

The burning of a hydrocarbon when oxygen supply is restricted, producing water ($H_2O$) along with toxic carbon monoxide ($CO$) and/or solid carbon soot ($C$).

Polymer

A large macromolecule constructed from many smaller, repeating chemical structural units termed monomers.

Microplastic

A minute synthetic plastic fragment typically measuring smaller than $5\,\text{mm}$ in size.

Bioaccumulation

The gradual accumulation and build-up of a substance within an organism over time because its rate of uptake exceeds its rate of elimination.

Sustainability

The practice of meeting current societal needs without compromising the ability of future generations to meet their own needs, across environmental, social, and economic pillars.

Weather

The short-term atmospheric conditions observed at a specific time and geographic place.

Climate

The long-term average pattern of weather conditions observed over a prolonged period, typically assessed over $30\,\text{years}$ or more.

Natural greenhouse effect

The natural warming mechanism whereby atmospheric greenhouse gases absorb and re-emit outgoing infrared radiation, maintaining Earth's temperature suitable for life.

Enhanced greenhouse effect

The amplified warming of Earth caused by anthropogenic greenhouse gas emissions trapping excessive heat in the atmosphere.

Climate change mitigation

Deliberate actions implemented to reduce or prevent the emission of greenhouse gases to slow down global warming.

Climate change adaptation

Adjustments and strategies adopted to manage, cope with, and reduce vulnerability to the unavoidable impacts of climate change.

Hypothesis

A testable, proposed explanation formulated to explain an observation or relationship.

Independent variable

The experimental factor deliberately changed or manipulated by the investigator.

Dependent variable

The factor being measured or observed in an investigation to determine the effect of changing the independent variable.

Controlled variables

All experimental variables intentionally kept constant to ensure an investigation constitutes a fair test.

Control group

A baseline group in an experiment that receives no treatment or a standard treatment to serve as a standard of comparison.

Validity

The degree to which an investigation fairly tests the hypothesis or question it intends to test by appropriately controlling all extraneous variables.

Reliability

The consistency and reproducibility of scientific results achieved by conducting repeat trials, increasing sample size, and calculating means.

Outlier

An anomalous data point that deviates distinctly from the overall trend observed across experimental trials.

Interpolation

The estimation of an unknown value located within the range of collected, observed data points.

Extrapolation

The prediction of a value lying outside the measured range of observed data points based on an established trend.