HUSO Global 2026 Grade 7–8 Open Round Science Study Guide

Comprehensive vocabulary flashcards covering key definitions across Biology, Chemistry, Physics, and Earth Science based on the HUSO Global 2026 Grade 7–8 Open Round Study Guide.

Carbon (biological role)

An element that can form four covalent bonds and connect to other carbon atoms in chains, branches, and rings to build large, complex molecules.

Carbohydrates

Molecules containing carbon, hydrogen, and oxygen that serve as a major energy source and structural material (e.g., glucose, starch, glycogen, cellulose).

Glucose

A simple sugar used as the primary substrate in cellular respiration to release energy.

Starch

A complex carbohydrate that stores energy in plants.

Glycogen

A complex carbohydrate that stores energy in animals.

Cellulose

A structural carbohydrate that forms plant cell walls.

Lipids

Biological molecules including fats and oils that provide long-term energy storage, body insulation, and form the basic structure of cell membranes.

Proteins

Molecules made from amino acids that function as enzymes, build and repair tissues, transport substances, and help defend the body.

Enzyme

A biological catalyst that speeds up a chemical reaction without being consumed in the process.

Denaturation

The loss of an enzyme's normal shape caused by very high temperatures or extreme pH, which reduces its function.

Nucleotide

The repeating structural unit of DNA and RNA, composed of a sugar, a phosphate group, and a nitrogen-containing base.

Cell Theory

The foundational biological principle stating that living organisms consist of one or more cells, the cell is the basic unit of structure and function, and new cells arise from pre-existing cells.

Nucleus

An organelle that contains most of a cell's DNA and helps control cell activities.

Cytoplasm

The jelly-like fluid within a cell where many chemical reactions take place.

Cell membrane

A selectively permeable boundary that controls which substances enter and leave the cell.

Ribosomes

Non-membrane-bound cell organelles responsible for building proteins.

Mitochondria

The organelles that serve as the site of most aerobic respiration, releasing usable energy in the form of ATP.

Chloroplasts

Plant and algal organelles containing chlorophyll that carry out photosynthesis.

Cell wall

A rigid supporting layer found outside the membrane in plants, composed mainly of cellulose.

Vacuole

A storage organelle; in plant cells, a large central vacuole maintains turgidity and keeps the cell firm.

Endoplasmic reticulum (ER)

A cellular network that helps produce and move materials; rough ER is studded with ribosomes.

Golgi apparatus

An organelle that modifies, sorts, and packages cellular products for transport.

Lysosomes

Organelles containing digestive enzymes that break down cellular waste and worn-out cell parts.

Eukaryote

An organism whose cells possess membrane-bound organelles and have their DNA enclosed within a nucleus.

Prokaryote

A single-celled organism (such as a bacterium) that lacks a nucleus and membrane-bound organelles, with its DNA lying in the cell interior.

Photosynthesis

The biological process in chloroplasts that captures light energy and stores it as chemical energy in glucose, converting carbon dioxide and water into glucose and oxygen.

Aerobic respiration

A chemical process requiring oxygen that completely breaks down glucose to release energy, producing carbon dioxide and water.

Anaerobic respiration

Respiration that releases energy from glucose without using oxygen, producing lactic acid in human muscles or ethanol and carbon dioxide in yeast.

Epithelial tissue

Animal tissue that covers body surfaces, lines organs and internal cavities, and forms many glands; functions in protection, absorption, and secretion.

Peristalsis

Wave-like muscle contractions that move food along the digestive tract, such as through the oesophagus to the stomach.

Villi

Tiny finger-like projections in the small intestine that increase surface area for the efficient absorption of digested nutrients.

Alveoli

Microscopic air sacs in the lungs with thin walls, a moist lining, and rich blood capillaries that enable gas exchange between air and blood.

Excretion

The biological process of removing metabolic waste products produced by chemical reactions inside cells.

Double circulation

A circulatory system where blood passes through the heart twice per complete body circuit: pulmonary circulation to the lungs and systemic circulation to the body.

Isotopes

Atoms of the same chemical element having the same number of protons but different numbers of neutrons.

Relative atomic mass

A weighted average of the masses of an element's naturally occurring isotopes relative to carbon-12.

Ionic bonding

Chemical bonding formed by electrostatic attraction between oppositely charged ions following electron transfer, typically from a metal to a non-metal.

Covalent bonding

Chemical bonding where atoms (usually non-metals) share pairs of electrons to achieve stable electron configurations.

Metallic bonding

The electrostatic attraction between positively charged metal ions and a surrounding sea of delocalised electrons.

VSEPR theory

Valence Shell Electron Pair Repulsion theory: electron pairs around a central atom repel each other and position themselves as far apart as possible to determine molecular geometry.

Empirical formula

The simplest whole-number ratio of atoms of each element present in a chemical compound.

Mole

A standard scientific unit for measuring large quantities of microscopic particles, where one mole equals Avogadro's number ($N_A$) of particles.

Oxidation

The loss of electrons or an increase in oxidation number during a chemical reaction.

Reduction

The gain of electrons or a decrease in oxidation number during a chemical reaction.

Brønsted–Lowry acid

A chemical species that donates a proton ($H^+$) to another substance.

Brønsted–Lowry base

A chemical species that accepts a proton ($H^+$) from another substance.

Scalar

A physical quantity that has magnitude only and no direction (e.g., speed, mass, distance, energy).

Vector

A physical quantity that possesses both magnitude and direction (e.g., velocity, force, acceleration, displacement).

Newton's First Law of Motion

The physical law stating that an object remains at rest or moves at a constant velocity unless acted upon by a non-zero net resultant force.

Newton's Second Law of Motion

The law stating that the acceleration of an object is directly proportional to the net force acting on it, expressed as $F_{\text{net}} = ma$.

Centripetal acceleration

Inwardly directed acceleration experienced by an object moving along a circular path, given by $a_c = \frac{v^2}{r}$.

Ohm's Law

The electrical relationship stating that current is proportional to voltage across a conductor, written as $V = IR$.

Troposphere

The lowest layer of Earth's atmosphere where almost all weather phenomena and atmospheric water vapour are concentrated.

Stratosphere

The layer of Earth's atmosphere situated above the troposphere that contains the ozone layer, which absorbs harmful ultraviolet radiation.

Relative humidity

The ratio of the actual amount of water vapour present in air to the maximum saturation amount the air can hold at that specific temperature, expressed as a percentage.

Aquifer

An underground permeable rock or sediment body capable of storing and transmitting extractable amounts of groundwater.

Water table

The boundary marking the upper surface of the underground zone saturated with groundwater.

Mineral

A naturally occurring, inorganic solid possessing a definite chemical composition and an ordered internal crystalline structure.

Igneous rock

Rock formed by the cooling and solidification of molten rock (magma beneath the surface or lava at the surface).

Sedimentary rock

Rock created through the deposition, compaction, and cementation of mineral particles, biological debris, or chemical precipitates.

Metamorphic rock

Rock produced by the transformation of existing rock through intense heat, pressure, and chemically active fluids without melting.

Kepler's First Law

The astronomical law establishing that every planet moves around the Sun in an elliptical orbit, with the Sun situated at one focus.

Kepler's Third Law

The law stating that the square of a planet's orbital period is directly proportional to the cube of its semi-major axis ($T^2 \propto a^3$).