Apr 24, 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 …

Chemical compound, any substance composed of identical molecules consisting of atoms of two or more chemical elements. All the matter in the universe is composed of the atoms of more …

May 12, 2025 · Chemical reactions differ from physical changes, which include changes of state, such as ice melting to water and water evaporating to vapor. If a physical change occurs, the …

Apr 29, 2025 · A chemical element is any substance that cannot be decomposed into simpler substances by ordinary chemical processes. Elements are the fundamental materials of which …

: a substance (such as an element or compound) that is made by a chemical process

Chemical formula, any of several kinds of expressions of the composition or structure of chemical compounds. The forms commonly encountered are empirical, molecular, structural, and …

The substances in a chemical reaction may be chemical elements, molecules, or compounds. The substances present at the start of a chemical reaction are called the reactants; the substances …

Cellular respiration, the process by which organisms combine oxygen with foodstuff molecules, diverting the chemical energy in these substances into life-sustaining activities and discarding, …

Chemical elements are classified or identified according to properties of their atoms. Each element has its own type of atoms—hydrogen consists of only hydrogen atoms, and helium …

Chemical energy is a form of potential energy that is in all substances. Food is the most important source of chemical energy for living things. The chemical energy in food is converted, or …