| Question | Answer |
|---|---|
| the smallest unit of a chemical substance that retains its properties | atom Scientists used a scanning tunnelling microscope to observe individual atoms on the surface of the crystal. |
| a group of two or more bonded atoms forming the smallest fundamental unit of a chemical compound | molecule A water molecule consists of two hydrogen atoms covalently bonded to one oxygen atom. |
| a substance made of two or more different chemical parts bonded together | compound Sodium chloride is a common compound formed by the ionic bonding of sodium and chlorine. |
| an electrically charged particle formed by gaining or losing one or more outer parts | ion When dissolved in water, table salt dissociates into sodium and chloride ions. |
| a positively charged subatomic particle found in the central core of every atom | proton The number of protons in the nucleus determines which chemical substance the atom represents. |
| a subatomic particle with no electric charge found in the atomic core | neutron Adding or removing a neutron from an atomic core changes its mass but not its chemical identity. |
| a negatively charged subatomic particle that orbits the atomic core | electron Electrons occupy specific energy levels and can jump between them by absorbing or emitting photons. |
| a variant form of a chemical substance that has the same number of protons but a different number of neutrons | isotope Carbon-14 is a radioactive isotope used to determine the age of ancient organic materials. |
| describing a substance that emits energy and particles due to the disintegration of its atomic nuclei | radioactive Uranium is a naturally occurring radioactive material used as fuel in nuclear power plants. |
| the spontaneous breakdown of an unstable atomic nucleus into smaller parts | decay The rate of radioactive decay is measured using half-lives, which vary enormously between different isotopes. |
| the time required for exactly fifty percent of a radioactive substance to disintegrate | half-life The half-life of carbon-14 is approximately 5,730 years, making it useful for dating archaeological finds. |
| a nuclear process in which light atomic nuclei combine to form a heavier one, releasing vast amounts of power | fusion Scientists are working to harness nuclear fusion as a virtually limitless source of clean power. |
| a nuclear process in which a heavy atomic core splits into two or more lighter fragments | fission Nuclear fission of uranium-235 is the primary reaction used in conventional nuclear power plants. |
| the capacity of a physical system to do work or produce heat | energy The law of conservation of energy states that it can neither be created nor destroyed, only transformed. |
| the form of power that a body possesses due to its motion | kinetic A rolling ball has kinetic power that increases with the square of its speed. |
| stored capacity to do work due to position or configuration | potential A book held above a table has gravitational potential that converts to motion when released. |
| relating to heat or temperature in a physical system | thermal Thermal insulation in buildings reduces heat loss and lowers heating costs during winter. |
| relating to waves that consist of oscillating electric and magnetic fields | electromagnetic Visible light is just a small portion of the full electromagnetic range of radiation. |
| the spatial distance between successive crests of a periodic oscillation | wavelength Different colours of light correspond to different wavelengths within the visible range. |
| the number of complete oscillation cycles that occur per unit of time | frequency Radio stations broadcast at specific frequencies measured in megahertz to avoid signal interference. |
| the maximum displacement of an oscillating body from its rest position | amplitude The amplitude of a sound wave determines the loudness perceived by the human ear. |
| a band of colours or frequencies produced when light or radiation is separated by its components | spectrum A prism separates white light into a continuous spectrum of colours ranging from red to violet. |
| light radiation with a shorter wavelength than violet, invisible to the human eye | ultraviolet Excessive exposure to ultraviolet rays from the sun can damage skin cells and increase cancer risk. |
| light radiation with a longer wavelength than red, perceived as heat | infrared Thermal cameras detect infrared emissions to create images based on temperature differences. |
| the emission and transmission of power in the form of waves or particles through space | radiation Background radiation from cosmic sources is constantly reaching the Earth's surface. |
| a discrete packet of light or electromagnetic radiation | photon Einstein proposed that light consists of photons, each carrying a specific quantity of power. |
| the smallest discrete unit of a physical property, such as power or angular momentum | quantum Quantum mechanics governs the behaviour of matter and radiation at the atomic scale. |
| a minute fragment of matter with observable physical properties such as mass and charge | particle The Large Hadron Collider accelerates subatomic particles to nearly the speed of light. |
| a periodic disturbance that transfers power through a medium or space without net movement of matter | wave Sound travels as a longitudinal wave through air, compressing and expanding gas molecules. |
| the speed of an object in a specified direction | velocity The velocity of a satellite must be precisely calculated to maintain a stable orbit around the Earth. |
| the rate of change of speed or direction of a moving body over time | acceleration A car that increases its speed from zero to sixty in five seconds has a high rate of acceleration. |
| the product of a body's mass and its speed in a given direction | momentum In a closed system, the total momentum before and after a collision remains constant. |
| a push or pull acting on a body that can change its motion or shape | force Newton's second law states that the net force on an object equals its mass multiplied by its acceleration. |
| the natural attractive pull between objects with mass, keeping planets in orbit | gravity Einstein's general theory of relativity describes gravity as the curvature of spacetime caused by mass. |
| the resistive contact pull that opposes the sliding motion of two surfaces | friction Engineers design brake pads to maximise friction between the pad and the disc for effective stopping. |
| the tendency of a body at rest to stay at rest and a body in motion to keep moving | inertia A passenger lurches forward when a car stops suddenly because of their body's inertia. |
| the quantity of matter in a body, measured in kilograms | mass Unlike weight, mass remains constant regardless of gravitational field strength. |
| the ratio of an object's mass to its occupied space | density Ice floats on water because it has a lower density than liquid water at the same temperature. |
| the amount of three-dimensional space occupied by a substance or object | volume Archimedes discovered that the volume of an irregularly shaped object can be measured by water displacement. |
| the continuous physical push exerted on a surface per unit area by a fluid or gas | pressure Atmospheric pressure decreases with altitude, which is why it is harder to breathe on mountaintops. |
| a space entirely devoid of matter, including air and other gases | vacuum Sound cannot travel through a vacuum because there are no molecules to carry the vibrations. |
| a material that does not easily allow heat or electric charge to pass through it | insulator Rubber is an excellent insulator and is used to coat electrical wires for safety. |
| the continuous flow of electric charge through a material | current An ammeter is used to measure the electric current flowing through a circuit. |
| the electric potential difference between two points in a circuit | voltage Increasing the voltage across a fixed resistor causes a proportional increase in current flow. |
| the opposition that a material offers to the flow of electric charge | resistance Ohm's law states that resistance equals voltage divided by current in a simple circuit. |
| a closed loop through which electric charge can flow continuously | circuit A simple circuit consists of a battery, wires, and a load such as a light bulb. |
| a material or object that attracts iron and certain metals by producing an invisible force field | magnet The Earth behaves like a giant magnet with a magnetic field that extends far into space. |
| the property of having two opposite poles, such as positive and negative or north and south | polarity The polarity of a battery determines the direction of current flow in a connected loop. |
| capable of being dissolved in a particular liquid | soluble Sugar is highly soluble in water, dissolving readily at room temperature. |
| incapable of being dissolved in a particular liquid | insoluble Sand is insoluble in water and settles to the bottom of the container. |
| a homogeneous mixture formed when one substance dissolves in another | solution A saline solution is commonly used in medical settings to rehydrate patients intravenously. |
| a liquid substance in which other materials can be dissolved | solvent Water is often called the universal solvent because it dissolves more substances than any other liquid. |
| the amount of a substance present per unit of mixture or liquid | concentration The concentration of dissolved oxygen in water affects the survival of aquatic organisms. |
| to make a liquid mixture less concentrated by adding more of the dissolving agent | dilute Chemists dilute strong acids with water before using them in laboratory experiments. |
| containing the maximum amount of dissolved substance that a liquid can hold at a given temperature | saturated A saturated solution will deposit excess crystals if the temperature is lowered. |
| a chemical substance with a pH below seven that donates hydrogen ions in aqueous mixtures | acid Hydrochloric acid is produced naturally in the human stomach to aid in digestion. |
| a chemical substance with a pH above seven that accepts hydrogen ions in aqueous mixtures | base Sodium hydroxide is a strong base commonly used in soap manufacturing. |
| a substance that increases the rate of a chemical process without itself being consumed | catalyst Platinum serves as a catalyst in catalytic converters, helping to reduce harmful vehicle emissions. |
| a chemical process in which substances interact to form new products | reaction The reaction between baking soda and vinegar produces carbon dioxide gas and water. |
| a chemical process in which a substance loses electrons or gains oxygen | oxidation The rusting of iron is a common example of oxidation that occurs in the presence of moisture. |
| a chemical process in which a substance gains electrons or loses oxygen | reduction In electroplating, the reduction of metal ions causes them to deposit as a thin layer on a surface. |
| the direct transition of a substance from solid to gas without passing through the liquid state | sublimation Dry ice undergoes sublimation at room temperature, turning directly into carbon dioxide gas. |
| the process by which a dissolved substance forms a regular solid structure as the liquid evaporates or cools | crystallisation Salt is harvested from seawater through evaporation and subsequent crystallisation in shallow ponds. |
| a large chain-like structure made of many repeating smaller molecular units | polymer Plastics are synthetic polymers that can be moulded into an enormous variety of shapes. |
| the bending of light as it passes from one transparent medium into another of different optical density | refraction A straw appears bent in a glass of water because of the refraction of light at the water's surface. |
| the spreading of waves as they pass through a narrow opening or around an obstacle | diffraction The colourful patterns on a compact disc are caused by the diffraction of white light. |
| the transfer of heat through a fluid by the upward movement of warmer, less dense regions | convection Convection currents in the Earth's mantle are believed to drive the movement of tectonic plates. |
| the transfer of heat through direct contact between molecules in a solid material | conduction Metals exhibit high rates of thermal conduction, which is why a metal spoon heats up quickly in hot soup. |
| a measure of the disorder or randomness in a thermodynamic system | entropy The second law of thermodynamics states that the total entropy of an isolated system always increases. |
| a transparent triangular optical body that separates white light into its component colours | prism Newton used a prism to demonstrate that white light is composed of a continuous band of colours. |
| not allowing light to pass through; impossible to see through | opaque Metals are opaque to visible light because free electrons absorb and re-emit incoming photons. |
| allowing some light to pass through but diffusing it so that objects behind cannot be clearly seen | translucent Frosted glass is translucent, permitting light to enter a room while maintaining privacy. |
| allowing light to pass through freely so that objects behind can be clearly seen | transparent Window glass is transparent, enabling natural sunlight to illuminate the interior of buildings. |
| the upward pushing effect exerted on a body immersed in a fluid, opposing its weight | buoyancy Ships float because the buoyancy of the water they displace is equal to their total weight. |
| a measure of a fluid's resistance to flow or deformation | viscosity Honey has a much higher viscosity than water, causing it to flow slowly when poured. |
| capable of being hammered or pressed into thin sheets without breaking | malleable Gold is one of the most malleable metals, capable of being beaten into extremely thin leaf. |
| capable of being drawn out into thin wires without breaking | ductile Copper is both ductile and an excellent electrical conductor, making it ideal for wiring. |
| the metabolic process by which microbes convert sugars into alcohol and carbon dioxide | fermentation The fermentation of grape juice by yeast is the fundamental process in winemaking. |
| a separation technique that heats a liquid mixture to collect its vapour and condense it back | distillation Crude oil is separated into useful fractions such as petrol and diesel through fractional distillation. |
| a machine that spins samples at high speed to separate components by their relative densities | centrifuge Blood samples are placed in a centrifuge to separate plasma from red and white cells. |
| a repetitive back-and-forth movement around an equilibrium position | oscillation The oscillation of a pendulum can be used to keep accurate time in a grandfather clock. |
| the phenomenon in which a system vibrates with maximum amplitude at a specific natural rate | resonance Opera singers can shatter glass by producing a note at the exact resonance point of the material. |
| a material that conducts electricity with zero resistance below a critical temperature | superconductor MRI machines use superconductor magnets cooled with liquid helium to generate powerful magnetic fields. |
| an instrument used to measure temperature, typically containing mercury or alcohol | thermometer The clinical thermometer was a vital invention for accurately diagnosing fever in medical practice. |
| an instrument used to measure atmospheric air weight, often to forecast weather | barometer A sudden drop in the barometer reading typically signals the approach of a storm system. |
| a rod through which electric charge enters or leaves a liquid or device during electrolysis | electrode In a battery, the positive electrode is called the cathode and the negative one is the anode. |
| a thin wire inside a light bulb that glows when heated by an electric charge | filament Edison's incandescent bulb used a carbon filament that could glow for over a thousand hours. |
| the positive terminal of an electrolytic cell toward which negative ions migrate | anode During electroplating, the metal to be deposited is placed at the anode of the electrolytic cell. |
| the negative terminal of an electrolytic cell toward which positive ions migrate | cathode In a cathode ray tube, electrons are emitted from the heated cathode and accelerated toward the screen. |
| a coil of wire that acts as an electromagnet when electric charge flows through it | solenoid A solenoid valve uses electromagnetic action to control the flow of fluids in industrial systems. |
| the total opposition a circuit presents to alternating current, combining resistance and reactance | impedance Matching the impedance of audio components ensures maximum power transfer and sound quality. |
| a rotational twisting effect produced by a perpendicular push applied at a distance from an axis | torque A longer wrench handle increases the torque applied to a bolt, making it easier to loosen. |
| the emission of visible light by a substance that has absorbed shorter-wavelength radiation | fluorescence Fluorescence microscopy allows scientists to visualise specific proteins inside living cells. |
| an instrument that separates and measures the components of a beam of light or radiation | spectrometer Astronomers use a spectrometer to determine the chemical composition of distant stars. |
| the process of adjusting an instrument so that its readings accurately correspond to a known standard | calibration Regular calibration of laboratory equipment is essential to ensure the accuracy of experimental results. |
| a junction of two different metals that generates a small voltage proportional to temperature | thermocouple Industrial furnaces use thermocouples to monitor and regulate internal temperatures with high precision. |
| an insulating material that does not conduct electricity but can be polarised by an electric field | dielectric The dielectric layer between the plates of a capacitor increases its ability to store charge. |
| the property of a material that generates an electric charge in response to mechanical stress | piezoelectric Quartz crystals exhibit a piezoelectric effect, which is exploited in precision timekeeping devices. |
| the process by which a substance takes in light, heat, or another form of radiant output | absorption The absorption of ultraviolet light by ozone in the stratosphere protects life on Earth. |
| relating to or measured in terms of the angle formed by two lines radiating from a common point | angular The angular velocity of a spinning wheel determines how quickly it completes each full rotation. |
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