Energy & Green Tech

Bacteria as climate heroes

To establish a carbon-neutral circular economy in the future, technologies are needed that use carbon dioxide as a raw material. In the form of formate, CO2 can be metabolized by certain bacteria.

Computer Sciences

Identifying individual proteins using nanopores and supercomputers

The amount and types of proteins our cells produce tell us important details about our health and how our bodies work. But the methods we have of identifying and quantifying individual proteins are inadequate to the task. ...

Energy & Green Tech

Ultrasound can enable faster, more sustainable battery recycling

Known by expectant parents as the technology that enables them to see their child for the first time, ultrasound can be used at extremely low frequencies to serve an entirely different purpose. Researchers at KTH Royal Institute ...


A more efficient way to find a more efficient battery

The pace of progress in the renewable energy sector is limited not only by the technology to capture energy from the sun, the wind, the oceans or the Earth's radiant heat, but also by the ability to effectively store and ...


Microfiber-based metafabric provides daytime radiative cooling

A team of researchers affiliated with multiple institutions in China has developed a micro-fiber based metafabric that provides wearers with daytime radiative cooling. In their paper published in the journal Science, the ...


Eco-friendly device detects real-time pipe damage

A researcher at University of Limerick has developed a low-cost, environmentally friendly sensor that can detect damage in pipelines and could save water as a result.

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An acid (from the Latin acidus/acēre meaning sour) is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red. Chemicals or substances having the property of an acid are said to be acidic.

Common examples of acids include acetic acid (in vinegar), sulfuric acid (used in car batteries), and tartaric acid (used in baking). As these three examples show, acids can be solutions, liquids, or solids. Gases such as hydrogen chloride can be acids as well. Strong acids and some concentrated weak acids are corrosive, but there are exceptions such as carboranes and boric acid.

There are three common definitions for acids: the Arrhenius definition, the Brønsted-Lowry definition, and the Lewis definition. The Arrhenius definition states that acids are substances which increase the concentration of hydronium ions (H3O+) in solution. The Brønsted-Lowry definition is an expansion: an acid is a substance which can act as a proton donor. Most acids encountered in everyday life are aqueous solutions, or can be dissolved in water, and these two definitions are most relevant. The reason why pHs of acids are less than 7 is that the concentration of hydronium ions is greater than 10−7 moles per liter. Since pH is defined as the negative logarithm of the concentration of hydronium ions, acids thus have pHs of less than 7. By the Brønsted-Lowry definition, any compound which can easily be deprotonated can be considered an acid. Examples include alcohols and amines which contain O-H or N-H fragments.

In chemistry, the Lewis definition of acidity is frequently encountered. Lewis acids are electron-pair acceptors. Examples of Lewis acids include all metal cations, and electron-deficient molecules such as boron trifluoride and aluminium trichloride. Hydronium ions are acids according to all three definitions. Interestingly, although alcohols and amines can be Brønsted-Lowry acids as mentioned above, they can also function as Lewis bases due to the lone pairs of electrons on their oxygen and nitrogen atoms.

This text uses material from Wikipedia, licensed under CC BY-SA