Physics & Chemistry

Physics is the the study of matter and its spatial motion; while it embraces the levels of nucleii, elementary particles and atoms, its domain relative to molecules and their interactions is more properly termed chemistry. The motion of particles is governed by the basic laws of physics including Newtonian mechanics (for large objects); electromagnetism; thermodynamics and quantum mechanics (in the case of molecular and smaller entities). The earliest forms of physics addressed are motions of celestial objects, and presently this field can be viewed as astrophysics. Physics also embraces the notions of the Theory of Relativity, so that the duality of space and time is addressed. Chemistry has taken on added importance in the last half century as the bridge between fundamental laws of nature and the understanding of cellular processes and replication of DNA, the basic molecule of organism genetic coding. 

  • Atmospheric lapse rate Featured Article Atmospheric lapse rate Atmospheric lapse rate

    The atmospheric lapse rate (  ) refers to the change of an atmospheric variable with a change of altitude, the variable being temperature unless specified... More »

  • Mercury Featured Article Mercury Mercury

    Mercury is a chemical element that occurs naturally in the environment and exists in several forms.  Previous Element: Gold Next Element:... More »

  • A Walk Through Time Featured Article A Walk Through Time A Walk Through Time

    The Evolution of Time Measurement through the Ages. A Walk Through Time Ancient Calendars Celestial bodies — the Sun, Moon, planets, and stars — have... More »

  • DNA Featured Article DNA DNA

    Deoxyribonucleic acid (DNA) is a long chain organic molecule that contains the coding for all metabolic and reproductive processes of all living organisms, save for certain... More »

  • Global Challenges/Chemistry Solutions Featured News Article Global Challenges/Chemistry Solutions Global Challenges/Chemistry Solutions

    Global Challenges/Chemistry Solutions Global Challenges/Chemistry Solutions is a series of podcasts describing some of the 21st century's most daunting problems, and... More »

  • Hydrogen Featured Article Hydrogen Hydrogen

    Hydrogen has an atomic structure consisting of one proton and one electron, making it the lightest of the elements and exists as diatomic molecules. In the solid state the element... More »

  • Uranium Featured Article Uranium Uranium

    Uranium is a radioactive element that occurs naturally in low concentrations (a few parts per million) in soil, rock, and surface and groundwater. It is the heaviest naturally... More »

  • Aluminum Featured Article Aluminum Aluminum

    Aluminum is a silver-white metal, very low density (less than three times as dense as water), yet relatively strong. In addition, aluminum is ductile; that is, it can be drawn... More »

Recently Updated
Concentration expressions and notations Last Updated on 2014-06-18 18:21:06 In chemistry and other sciences, engineering and in fairly common usage, concentration is the measure of how much of a given substance there is in a given mixture of substances. There are many different notations and quantitative expressions of concentration.[1] The most commonly used expressions are discussed below: The mole fraction is a measure of the concentration of a component substance in a mixture of substances. It is defined as the number of moles of a component substance in a mixture divided by the total number of moles of the mixture.[2][3] The mole percent  (also referred to as the molar percent) is usually denoted by mole % and is equal to 100 times the mole fraction. The mass fraction is also a measure of the concentration of a component substance in a mixture of substances. It is defined as the mass of a component substance in a mixture divided by the total... More »
Los Alamos National Laboratory Last Updated on 2014-06-18 18:15:17 Los Alamos National Laboratory (LANL), located in Los Alamos, New Mexico, is one of several U.S. Department of Energy (DOE) national laboratories. It is noteworthy as the site where the world's first nuclear weapon was developed under a heavy cloak of secrecy during World War II, and has been known variously as Site Y, Los Alamos Laboratory, and Los Alamos Scientific Laboratory. Today, it is recognized as one of the world's leading science and technology institutes. Since June 2006, LANL has been managed and operated by Los Alamos National Security, LLC (LANS).[1] LANL's self-stated mission is to ensure the safety, security, and reliability of the nation's nuclear deterrent.[2] Its research work serves to advance bioscience, chemistry, computer science, Earth and environmental sciences, materials science, and physics disciplines. The Manhattan Project was the... More »
Photovoltaics Last Updated on 2014-06-10 18:44:01 In recent decades the imminence of an energy crisis has become a common discussion topic. We will eventually deplete all fossil fuels that can be economically extracted.[1] Depletion is not the only issue involved in the use of fossil fuels; the combustion process releases carbon dioxide which can or is changing global climate. Fossil fuels, such as coal, natural gas, and oil, are the most common energy sources used today. When combusted to create energy, these fuels release large amounts of carbon dioxide and other greenhouse gases. These emissions cause a warming effect on the planet. The exact results of this warming are not certain, but most predictions verge on the catastrophic. In order to curb this warming effect and free ourselves from fossil fuel use, we must reduce, and ultimately replace, them as an energy source. One promising renewable energy source involves capturing... More »
Earth's atmospheric air Last Updated on 2014-04-02 14:56:48 The Earth's atmospheric air is a colorless, odorless and tasteless mixture of gases consisting mostly of nitrogen (N2) and oxygen (O2). It is the part of Earth's atmosphere that humans and all other animals breathe in order to obtain the oxygen needed to sustain life. The Earth's atmosphere not only contains the air we breathe, it also holds clouds of moisture (water vapor) that become the water we drink. Furthermore, it protects us from meteors and harmful solar radiation and warms the Earth's surface by heat retention. In effect, the atmosphere is an envelope that protects all life on Earth. The air may contain pollutants that originate from a variety of sources such as our industries and our vehicles, and can directly or indirectly affect our health and the natural environment. These effects may be experienced near the sources of air pollution and some air... More »
Energy quality Last Updated on 2014-03-06 16:45:22 Energy quality refers to differences in the ability of a unit of energy to produce goods and services for people. The usefulness of an energy system is determined by a complex combination of physical, technical, economic, and social attributes. These include gravimetric and volumetric energy density, power density, emissions, cost and efficiency of conversion, financial risk, amenability to storage, risk to human health, and ease of transport. No single metric of an energy system captures all such attributes. It stands to reason, therefore, that a comprehensive and balanced comparison of energy technologies should employ a range of metrics, with their strengths and weaknesses duly noted. The most common way to measure energy is by heat content because all forms of energy can be completely converted to heat (Btus, joules, calories, kilowatt-hours). The aggregation of... More »