Visionlearning Glossary

The theoretical lowest temperature possible at which all molecular motion ceases. Absolute zero, 0 K or -273.15°C, has never been reached.

Used in the following modules: Matter: States of Matter, Temperature

In science, the term accuracy describes how well a measurement approximates the theoretically correct value of that measurement, for example, how close an arrow strikes to the center of a target. Accuracy provides a measure of the systematic error associated with a value. Compare to precision. See the module Uncertainty.

Used in the following modules: Data: Analysis and Interpretation, Data: Uncertainty, Error, and Confidence, Gravity, Minerals II, Research Methods: Description, Research Methods: Modeling, Using Science News in Teaching

Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different scientists (listed in parentheses). 1) (Arrhenius) a compound that releases hydrogen ions (H+) in solution; 2) (Brønsted-Lowry) a compound capable of donating hydrogen ions, 3) (Lewis) a compound that can accept a pair of electrons from a base.

Used in the following modules: Acids and Bases, DNA I, DNA II, Fats and Proteins, Matter, Minerals II, Research Methods: Modeling, Scientific Communication: Peer Review, The Carbon Cycle, The Nitrogen Cycle

Rain with a pH less than 5.

Used in the following modules: The Nitrogen Cycle

The energy required to initiate a chemical reaction or process, abbreviated E_a. For example, a cigarette lighter requires activation energy (provided in the form of a spark) to initiate the reaction of fuel with oxygen.

Used in the following modules: Chemical Equations, Chemical Reactions

Welsh astronomer, born near Launceston, Cornwall (1819-1892). He successfully predicted the existence of a then-unknown planet (Neptune) based on perturbations in Uranus’ orbit. He also studied the Leonid meteor shower, successfully predicting its occurrence and proving its association with Tempel’s Comet. For further information, see John Couch Adams.

Used in the following modules: Gravity

To adhere in an extremely thin layer of molecules (as of gases, solutes, or liquids) to the surfaces of solid bodies or liquids with which a substance is in contact.

The semi-molten layer of the earth which starts at ~70-200 km depth and ends at 660 km depth. The aesthenosphere is part of the mantle, and is composed primarily of the rock peridotite. The aesthenosphere can flow very slowly, allowing rigid pieces of the lithosphere to move around on top of it.

Used in the following modules: Earth Structure

(Geroge Bauer) German geologist and medical doctor, born in Glauchau, Saxony (1494-1555). Agricola wrote several influential geological manuscripts, including De Natura Fossilium (1546), De Ortu et Causis Subterraneorum (1546) and De Re Metallica (published posthumously in 1556). The later is his most influential work, being a compendium of everything then known about mining, including (but not limited to) equipment, methods of surveying for and extracting minerals, mine administration, and the occupational diseases of miners. For further information, see Georgius Agricola.

Used in the following modules: Minerals I

A medieval chemical philosophy concerned principally with the transformation of base metals into gold, and the discovery of an elixir of life.

An organic compound containing a hydroxyl group. Common examples include methanol (CH₃OH) and ethanol (CH₃CH₂OH).

Used in the following modules: Organic Chemistry, Temperature

The Latinized name for the Muslim scientist Abū ‘Alī al-Hasan ibn al-Hasan ibn al-Haytham who was born in Basra, Mesopotamia (Iraq) (965-1039 CE). Alhazen made significant contributions in the fields of astronomy, mathematics, medicine, and most significantly, optics. His work in optics irrefutably proved that vision is a function of external light rays entering the human eye; and his rigorous and quantitative approach formed the basis of the modern experimental method in science. For further information see Alhazen

Used in the following modules: Light I, Research Methods: Experimentation, Research Methods: The Practice of Science, Scientific Communication: Utilizing the Scientific Literature

A group of hydrocarbons with the general formula C_nH_(2n+2). Alkanes contain no carbon-carbon multiple bonds; common examples include methane and propane.

Used in the following modules: Organic Chemistry

A group of hydrocarbons with the general formula C_nH_(2n). Alkenes contain at least one carbon-carbon double bond; common examples include ethylene.

Used in the following modules: Organic Chemistry

A group of hydrocarbons with the general formula C_nH_(2n-2). Alkynes contain at least one carbon-carbon triple bond; common examples include ethyne also known as acetylene.

Used in the following modules: Organic Chemistry

A variation of a genetic element, usually resulting in a distinct trait.

Used in the following modules: Genetics I

A type of particle that is ejected from radioactive nuclei. Alpha particles consist of two protons and two neutrons and thus are equivalent to helium nuclei.

Used in the following modules: Atomic Theory I, Nuclear Chemistry

In statistical testing, an alternative hypothesis (H₁) is a statement describing the possibility that an observed result or effect is genuine. The alternative hypothesis is always compared to a null hypothesis (H₀), and H₁ is not accepted until statistical testing shows that it should be accepted in favor of H₀. For example, in an evaluation of data regarding the pain relieving properties of a new drug, the alternative hypothesis would state that the new drug has an effect on pain relief compared to a control. Accepting H₁ does not indicate that the observed result or effect is large or important, simply that it is favored in terms of probability of the outcome.

Used in the following modules: The Case of the Ivory-billed Woodpecker

Pertaining to an alveolus.

Used in the following modules: Absorption, Distribution and Storage of Chemicals

The plural of alveolus.

Used in the following modules: Absorption, Distribution and Storage of Chemicals

A small sac-like structure in the body, especially common in the lung. A lung alveolus has extremely thin walls that aid in the exchange of gases including O₂ and CO₂.

Biochemical molecules that contain at least one amine group (-NH₂) and at least one carboxylic acid group (-COOH) and conform to the general formula NH₂-R-COOH, where R is an organic molecule. Amino acids are essential basic building blocks of proteins.

Used in the following modules: DNA I, Fats and Proteins

French mathematician born in Poleymieux, Lyon (1775-1836). Ampére researched metaphysics, physics, and chemistry, but he focused on mathematics, which he taught at the Ecole Polytechnique in Paris. His key contributions to science include his work on partial differential equations, the discovery of fluorine, and studies on the wave theory of light. His most important work was the Memoir on the Mathematical Theory of Electrodynamic Phenomena, Uniquely Deduced from Experience, in which he described a mathematical derivation for the electrodynamic force law. The Amp (a measurement of electrical current) is named in his honor. For further information see Andre Ampére.

Having the ability to live both on land and in water.

Used in the following modules: Adaptation

A convergent plate boundary, where oceanic crust is being subducted beneath continental crust. Named after the Andes Mountains in South America, which are the classic example of a continent-ocean convergence.

Used in the following modules: Plate Tectonics II

An extrusive igneous rock of intermediate composition, often gray in color. The main minerals present in andesite are plagioclase and hornblende. The word “andesite” comes from the Andes Mountains in South America, where this rock type is common. Around the world, andesitic magma erupts out of volcanoes along convergent boundaries, and its intrusive equivalent is diorite.

Used in the following modules: Minerals III, The Rock Cycle

A unit of length equivalent to 10^-10 meters. 1Å = 0.0000000001 m.

An ion that migrates to the anode in an electrical cell; a negatively charged ion.

Used in the following modules: Minerals II, Minerals III

A positively charged terminal in an electrical cell.

A deviation from the normal or expected, sometimes expressed with respect to an average value. Anomalies are described in many kinds of data, and are features of datasets that require explanation.

Male part of a flowering plant that holds pollen.

Used in the following modules: Genetics I, Scientists and the Scientific Community

A porous and permeable body of rock or sediment through which groundwater flows.

Used in the following modules: The Hydrologic Cycle

Greek mathematician, born in Syracuse, Sicily (287-212 BCE). Little is known about Archimedes’ life, but he is best known for devising the water displacement method of measuring the volume of an irregularly-shaped object (which he possibly conceived of while getting into his bathtub). He is also credited with developing the foundations of integral calculus and mathematical physics. For further information see Archimedes.

Used in the following modules: Density

A Greek philosopher born in Stagira (384-322 BCE). He joined Plato’s Academy in Athens (then being run by Eudoxus) at the age of 17. After attending the academy, he taught there for 20 years before founding his own school, the Lyceum. He is remembered primarily for his works on deductive logic and the use of philosophical reasoning to address questions about the natural world. For further information see Aristotle.

Used in the following modules: Charles Darwin I, Charles Darwin III, Light I, Matter, Research Methods: The Practice of Science, Taxonomy I

Swedish physical chemist born in Vik (1859-1927). Arrhenius is most famous for what is now known as the Arrhenius equation, which relates the rate of chemical reactions to temperature and activation energy. Arrhenius was awarded the Royal Society’s Davy medal and the Faraday medal of the Chemical Society in 1914, and the Nobel Prize for Chemistry in 1903 based on his early work on the conductivity of electrolytes in solution. For further information see Svante Arrhenius.

Used in the following modules: Acids and Bases

The smallest unit of an element that retains the chemical properties of the element. Atoms can exist alone or in combinations with other atoms forming molecules.

Used in the following modules: Atomic Theory I, Atomic Theory II, Carbohydrates, Chemical Bonding, Chemical Equations, Chemical Reactions, Data: Uncertainty, Error, and Confidence, Data: Using Graphs and Visual Data, DNA I, DNA II, Earth's Atmosphere, Fats and Proteins, Matter, Matter: States of Matter, Minerals I, Minerals III, Nuclear Chemistry, Organic Chemistry, Research Methods: Modeling, Scientific Ethics, Teaching Effectively with Multimedia, The Mole, The Nitrogen Cycle, The Periodic Table of Elements, Water

The average mass of an atom of an element, usually expressed in atomic mass units. The term is often used interchangeably with atomic weight.

Used in the following modules: Atomic Theory I, Atomic Theory II, Nuclear Chemistry

One atomic mass unit (amu or u) is defined as 1/12 the mass of the standard carbon-12 isotope, or 1.66 × 10^-27 kg.

The number of protons in an atomic nucleus.

Used in the following modules: Atomic Theory II, Nuclear Chemistry, The Periodic Table of Elements

Compare with Bohr radius and hartree.A system of non-SI units used in quantum chemistry to simplify calculations and mathematical expressions. The definitions of atomic units include physical constants (like the speed of light, the rest mass of the electron, and other quantities that never change), so that all constants drop out of expressions when atomic units are used.

As listed on the periodic table, the atomic weight is a weighted average of the masses of stable isotopes of an element that occur in nature. Given in grams, the atomic weight is the weight of one mole of atoms of an element. Atomic weight is often used interchangeably with atomic mass.

Used in the following modules: Matter, Nuclear Chemistry, The Mole, The Periodic Table of Elements

The behavior of waves as they radiate out from a source. As distance from the source increases, intensity of the waves decreases. Attenuation occurs because the same amount of energy is being spread out over a larger area.

Italian chemist and mathematician born in Turin (1776-1856). Avogadro was schooled to be an ecclesiastical lawyer, but retained an interest in natural philosophy, and studied mathematics and physics on his own. In 1811, Avogadro made the first distinction between molecules and atoms. He further suggested Avogadro’s Principle: equal volumes of gas at the same pressure and temperature contain the same number of molecules. Avogadro’s number, which defines the number of atoms in a mole, is named after him for his disambiguation of molecules. For more information see Amadeo Avogadro.

Used in the following modules: The Mole