Chemical and Nuclear Reactions

Comprehensive practice flashcards defining essential vocabulary across chemical and nuclear reactions, covering conservation laws, reaction classifications, reaction kinetics, radiation types, radioactive decay, nuclear energy, and safety.

Reactants

The starting substances that react together in a chemical reaction, written to the left of the reaction arrow in a chemical equation.

Products

The new substances formed as a result of a chemical reaction, written to the right of the reaction arrow in a chemical equation.

Law of Conservation of Mass

A fundamental scientific law established by Antoine-Laurent Lavoisier stating that during a chemical reaction, matter can be neither created nor destroyed.

Open System

A system in which matter and energy can be freely transferred in or out from its surroundings during a reaction.

Closed System

A system that does not allow matter to be transferred between itself and its surroundings, ensuring the total mass of the reactants equals the total mass of the products.

Law of Constant Proportions

A chemical law stating that a compound, regardless of how it is formed, always contains the same relative amounts of each element in fixed proportions.

Aqueous Solution

A solution in which a substance is dissolved in water, denoted by the state symbol $(aq)$ in chemical equations.

Coefficients

Whole numbers placed in front of chemical formulae in an equation to balance the number of atoms of each element on both sides of the reaction.

Acid

A corrosive substance with a sour taste and a $pH$ of less than $7$ that reacts with solid substances such as metals, marble, and tooth enamel.

Base

A chemical substance with a bitter taste, a slippery or soapy feel, and a $pH$ greater than $7$ that can react with and neutralise an acid.

Alkali

A base that is soluble and can dissolve in water.

pH Scale

A scale ranging from $1$ to $14$ measuring the concentration of hydrogen ions ($[H^+]$) in a solution, defined by the formula $pH = -\text{log}([H^+])$.

Universal Indicator

A mixture of dye indicators that changes colour over the full range of $pH$ from $1$ to $14$, turning pink in strong acid, green in neutral solutions, and blue in strong base.

Neutralisation Reaction

A chemical reaction between an acid and a base that produces water and an ionic salt, resulting in a neutral solution ($pH = 7$).

Salt (Chemistry)

Any ionic compound composed of a positive metal cation and a negative non-metal anion formed as a product of a neutralisation reaction.

Antacid

A medical product containing weak bases, such as magnesium hydroxide ($Mg(OH)_2$) or aluminium hydroxide ($Al(OH)_3$), used to neutralise excess stomach hydrochloric acid without producing carbon dioxide gas.

Bile

A greenish-yellow alkaline fluid secreted by the gall bladder into the duodenum to neutralise stomach acid mixed with partly digested food.

Synthesis Reaction

A reaction in which two or more reactants combine to produce a single product, typically accompanied by the release of energy as heat or light.

Decomposition Reaction

A chemical reaction in which a single compound breaks down into two or more simpler substances.

Single Displacement Reaction

A reaction where a more reactive metal pushes a less reactive metal out of a compound and takes its place.

Double Displacement Reaction

A reaction in which two aqueous ionic compounds exchange cations, effectively swapping partners to form new compounds.

Activity Series

A list ranking metallic elements in decreasing order of their chemical reactivity, used to predict whether a displacement reaction will occur.

Precipitate

An insoluble solid that forms and separates out from a solution during a double displacement reaction between two aqueous solutions.

SNAP Rule

A solubility guideline stating that all compounds containing Sodium ($Na^+$), Nitrate ($NO_3^-$), Ammonium ($NH_4^+$), or Potassium ($K^+$) ions are completely soluble in water and never form precipitates.

Reaction Rate

The speed at which a chemical reaction occurs, measured by the consumption of reactants or formation of products over time.

Catalyst

A substance that increases the rate of a chemical reaction without being consumed or permanently altered in the process.

Catalytic Converter

A vehicle exhaust device containing honeycomb ceramic coated with platinum, rhodium, or palladium that catalyses the conversion of toxic gases into nitrogen, oxygen, and carbon dioxide.

Enzyme

A biological catalyst produced by living organisms that accelerates vital chemical reactions within cells, such as catalase breaking down toxic hydrogen peroxide into water and oxygen.

Chemiluminescence

The production and emission of light as a direct result of a chemical reaction, such as the reaction between luminol and hydrogen peroxide in the presence of iron.

Bioluminescence

A natural form of chemiluminescence in which light is generated inside a living organism via a reaction between the pigment luciferin and oxygen, catalysed by luciferase.

Cherenkov Effect

The luminous blue glow produced around a nuclear reactor core when charged particles pass through water at a speed exceeding the speed of light in that medium, transferring energy that water molecules release as blue light.

Isotopes

Atoms of the same element that contain the same number of protons (same atomic number) but different numbers of neutrons (different mass numbers).

Strong Nuclear Force

The powerful attractive nuclear force that binds protons and neutrons together within an atomic nucleus, preventing electrostatic repulsion between positively charged protons from tearing it apart.

Band of Stability

The specific region on a graph of neutron number versus proton number where stable, non-decaying nuclei are situated.

Radioisotopes

Unstable isotopes whose nuclei break apart spontaneously via radioactive decay, emitting nuclear radiation and forming smaller, more stable nuclei.

Half-Life

The duration of time required for half of the radioactive nuclei present in a given sample to undergo decay.

Radiometric Dating

The scientific method of calculating the age of an object or rock by measuring the relative decay proportions of radioactive parent isotopes to stable daughter isotopes.

Radiocarbon Dating

A radiometric dating method for organic relics up to approximately $55\,000$ years old that calculates time since death based on the ratio of decaying carbon-14 ($^{14}_{\phantom{0}6}C$) to stable carbon-12 ($^{12}_{\phantom{0}6}C$).

Ionising Radiation

High-energy radiation capable of removing electrons from nearby atoms and molecules, converting them into charged ions.

Alpha Particle

A positively charged nuclear particle consisting of two protons and two neutrons ($^4_2\text{He}$) with high ionising ability and very low penetrating power, easily stopped by a sheet of paper or dead skin cells.

Beta Particle

A high-speed electron ($^0_{-1}e$) or positron ($^0_1e$) emitted from an unstable nucleus during decay, having medium penetrating power capable of entering living tissue until stopped by thin aluminium or plastic.

Gamma Ray

High-energy electromagnetic wave (photon) with no mass or charge emitted during nuclear reactions, possessing very high penetrating power that requires thick lead or concrete to stop.

Neutron Radiation

A form of indirectly ionising radiation consisting of free neutrons released during decay that collide with and destabilise adjacent atomic nuclei, causing them to emit secondary ionising radiation.

Background Radiation

The constant, low-level ionising radiation from natural and artificial environmental sources (such as cosmic rays, rocks, soil, and radon gas) that humans are continuously exposed to without harm.

Human Dose Equivalent

A measurement of the biological effect and tissue damage caused by radiation absorption, taking into account radiation type and exposure conditions, expressed in millisieverts ($\text{mSv}$).

Nuclear Fission

A nuclear reaction in which an unstable, heavy nucleus splits into smaller daughter nuclei while releasing free neutrons and energy.

Nuclear Fusion

A nuclear reaction occurring under extremely high temperatures where two light nuclei join together to form a heavier nucleus, releasing vast quantities of energy.

Nuclear Chain Reaction

A self-sustaining sequence of nuclear fission events where neutrons produced by one fission split subsequent fissionable nuclei in expanding numbers.

Critical Mass

The minimum mass of fissionable radioactive material needed to sustain an uncontrolled nuclear chain reaction.

Quarks

Elementary subatomic particles existing in six flavours (up, down, strange, top, bottom, and charmed) that are bound by gluons to construct protons and neutrons.

Positron Emission Tomography (PET)

A medical imaging procedure in which an administered radioisotope emits positrons that generate gamma rays, detected by rotating ring scanners to build 3D anatomical image slices of tissues or tumours.

Radiotherapy

The clinical treatment of cancer using targeted ionising radiation, administered externally via directed beams or internally (brachytherapy) by placing radioisotopes near tumours.

Moderator

A component in a nuclear reactor core (commonly heavy water or graphite) that slows down fast fission neutrons to the speed required to induce further fission in uranium-235.

Control Rods

Rods made of neutron-absorbing materials such as cadmium or boron that are raised or lowered into a reactor core to regulate or halt the rate of the nuclear chain reaction.

Enrichment

The technological process used to increase the concentration of fissionable uranium-235 ($^{235}_{\phantom{0}92}U$) in natural uranium from roughly $1\%$ up to $3\text{--}5\%$ for use as reactor fuel.

Vitrification

A radioactive waste management method where high-level liquid nuclear waste is mixed with glass-forming silica at high temperatures to produce an insoluble, stable solid glass for long-term storage.

Nuclear Meltdown

A catastrophic reactor failure where cooling failure causes the fuel rods to overheat and melt down through the core floor and containment vessel, releasing radioactive materials into the environment.