Year 9 Science: Data Science, Chemistry, Energy, and Homeostasis

Comprehensive vocabulary flashcards covering Year 9 Science topics including scientific inquiry, data analysis and statistics, experimental errors, atomic structure and bonding, energy laws, and homeostatic regulation.

SI (International System) Units

Standardised units of measurement based on the metric system that scientists use worldwide, including metres ($\text{m}$) for length, kilograms ($\text{kg}$) for mass, seconds ($\text{s}$) for time, and Kelvin ($\text{K}$) for temperature.

Mean

The average value calculated in descriptive statistics by summing all data points and dividing by the total number of points.

Median

The middle value in a set of ordered data.

Mode

The most frequently occurring or common value in a data set.

Range

The simplest measure of variability, calculated as the difference between the maximum and minimum values in a dataset ($\text{Range} = \max(x) - \min(x)$).

Interquartile Range (IQR)

The measure of the spread of the middle $50\%$ of data, representing the difference between the third quartile ($Q_3$) and the first quartile ($Q_1$), calculated as $\text{IQR} = Q_3 - Q_1$.

Variance

A measurement of how far each number in a data set is from the mean (average), and thus from every other number in the set.

Standard Deviation

The square root of variance ($\sigma = \sqrt{\sigma^2}$ or $s = \sqrt{s^2}$), which brings the measure of data dispersion back into original units.

Accuracy

The extent to which a measured value agrees with its true reference value, reflecting how close a measurement is to the correct baseline.

Reliability

The extent to which the findings of repeated experiments, conducted under identical or similar conditions, agree with each other (the consistency of results across repeated tests).

Validity

The extent to which an experiment addresses the question under investigation, ensuring it tests what it was intended to test (the direct effect of the independent variable on the dependent variable).

Inquiry Question

A question asked about an observation (beginning with How, What, When, Who, Which, Why, or Where) that initiates a scientific investigation.

Hypothesis

A testable statement and proposed explanation of how things work that links the independent and dependent variables (e.g., 'if $x$ increases, $y$ decreases').

Independent Variable

The factor that is deliberately changed or manipulated by the experimenter (the cause).

Dependent Variable

The factor that is measured or observed to assess the effect of the experiment (the effect).

Controlled Variable

All factors kept constant throughout an experiment to ensure that the test remains fair.

First-hand Investigation

A process where you collect data, observations, or evidence yourself through direct experience, experimentation, or primary research rather than relying on secondary reports.

Random Error

An experimental error caused by unpredictable fluctuations, such as environmental changes or background noise, resulting in values scattered both above and below the true value.

Systematic Error

An experimental error that occurs consistently due to flaws in the apparatus or experimental design, causing measurements to fall consistently all above or all below the actual value.

Strong Nuclear Force

The fundamental force that binds protons and neutrons together to form atomic nuclei.

Electromagnetic Force

The force occurring between electrically charged particles, consisting of combined electric and magnetic forces.

Valence Electrons

The electrons located in the outermost energy level or shell of an atom.

Noble Gases

Group $18$ elements (also known as inert gases) that have a full outermost electron shell, making them chemically unreactive and highly stable under normal conditions.

Octet Rule

The tendency of atoms to react and bond so that they acquire a stable outer shell of $8$ valence electrons, similar to noble gases (with helium being complete with $2$).

Cation

A positively charged ion formed when an atom loses one or more valence electrons.

Anion

A negatively charged ion formed when an atom gains one or more valence electrons.

Ionic Bond

The electrostatic attraction between oppositely charged ions, formed when electrons are completely transferred from one atom (typically a metal) to another (typically a non-metal).

Covalent Bond

A chemical bond formed between non-metal atoms through the sharing of one or more pairs of electrons to achieve a full outer shell.

Metallic Bond

The force of attraction between a lattice of positively charged metal ions and a surrounding sea of delocalised valence electrons.

Ductile

The mechanical property of metals that allows them to be drawn or pulled into thin wires because their atoms are arranged in rows.

Malleable

The mechanical property of metals that allows them to be hammered or rolled into shapes because layers of atoms can slide over one another.

Fractional Distillation

A separation process that separates different hydrocarbon fractions from crude oil based on differences in their boiling points.

Law of Conservation of Energy

The fundamental physical law stating that energy cannot be created or destroyed, only transformed from one form to another, meaning the total energy in an isolated system remains constant ($KE_{\text{initial}} + PE_{\text{initial}} = KE_{\text{final}} + PE_{\text{final}}$).

Energy Efficiency

The measure of useful energy obtained from a process compared to the total energy input, expressed as $\text{Efficiency} = \left(\frac{\text{Useful Energy Output}}{\text{Total Energy Input}}\right) \times 100$.

Isolated System

A physical system that does not exchange energy or matter with its surroundings, preserving a constant total internal energy.

Biogas

A renewable fuel gas produced by the biological breakdown of organic waste (such as food or manure) in the absence of oxygen.

Biomass

Organic material from living plants and animals that can be burned directly or converted into fuel.

Homeostasis

The physiological process by which internal conditions (such as temperature, pH, blood glucose, and water balance) are maintained within a stable, narrow range despite external variations.

Negative Feedback Loop

A homeostatic control mechanism that detects a change away from a set point and triggers a response that reverses the change to restore normal conditions.

Positive Feedback Loop

A physiological mechanism that amplifies and strengthens an initial change, driving a process forward until a specific terminal outcome is reached.

Endocrine System

A chemical communication network of glands that secrete hormones directly into the bloodstream to regulate processes such as metabolism, growth, and reproduction.

Hormones

Chemical messengers secreted by endocrine glands that travel through the blood to initiate specific responses in target cells equipped with matching receptors.