Oct 12, 2025 · Polymer, any of a class of natural or synthetic substances composed of very large molecules that are multiples of simpler chemical units. Polymers make up many of the …

Sep 26, 2025 · All the matter in the universe is composed of the atoms of more than 100 different chemical elements, which are found both in pure form and combined in chemical compounds.

Oct 10, 2025 · A chemical reaction is a process in which one or more substances, the reactants, are converted to one or more different substances, the products. Substances are either …

Sep 23, 2025 · The identification of pure substances and the analysis of chemical mixtures enable all other chemical disciplines to flourish. The importance of analytical chemistry has never …

On This Day In History: anniversaries, birthdays, major events, and time capsules. This day's facts in the arts, politics, and sciences.

calcium Calcium is the fifth most abundant chemical element in Earth’s crust. It also makes up 2 percent of the human body. In the body calcium helps form bones and teeth and keeps…

Sep 13, 2025 · Neon, chemical element, inert gas of Group 18 (noble gases) of the periodic table, used in electric signs and fluorescent lamps. Colorless, odorless, tasteless, and lighter than …

Removal of Mohammed Morsi, Obama’s “red line” in Syria, and chemical weapons The Iran nuclear deal, the Bipartisan Budget Act of 2013, and the Ukraine crisis

Sep 12, 2025 · The chemical was widely used, though many species of insects rapidly developed resistant populations. As a result of repeated sprayings, DDT accumulated in soils in …

Sep 18, 2025 · magnesium (Mg), chemical element, one of the alkaline-earth metals of Group 2 (IIa) of the periodic table, and the lightest structural metal. Its compounds are widely used in …