Chemical substance - Wikipedia
A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. [1] [2] Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combined without reacting, they may form a chemical mixture. [3]
PubChem
PubChem is the world's largest collection of freely accessible chemical information. Search chemicals by name, molecular formula, structure, and other identifiers. Find chemical and physical properties, biological activities, safety and toxicity information, patents, …
What Is a Chemical? Definition and Examples - Science Notes and …
2023年10月15日 · A chemical is a substance with a specific composition. It is an element, an alloy, or a compound made up of two or more elements combined in a fixed ratio. For instance, water (H 2 O) is a chemical because it consists of hydrogen and oxygen combined in a 2:1 ratio.
Chemical compound | Definition, Examples, & Types | Britannica
2024年10月18日 · 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 than 100 different chemical elements, which are found both in pure form and combined in chemical compounds.
Chemistry | Definition, Topics, Types, History, & Facts | Britannica
2024年11月5日 · Chemistry, the science of the properties, composition, and structure of substances (defined as elements and compounds), the transformations they undergo, and the energy that is released or absorbed during these processes.
Chemical substance - Simple English Wikipedia, the free …
A chemical substance is any material with a known chemical composition. [1] For example, water has the same properties and the same ratio of hydrogen to oxygen whether it came from a river or was made in a laboratory .
3.1: Types of Chemical Compounds and their Formulas
2023年7月12日 · There are two fundamentally different kinds of chemical bonds (covalent and ionic) that cause substances to have very different properties. The composition of a compound is represented by an empirical or molecular formula, each consisting of at least one formula unit.Contributors
Chemical element | Definition, Origins, Distribution, & Facts
A chemical element is any substance that cannot be decomposed into simpler substances by ordinary chemical processes. Elements are the fundamental materials of which all matter is composed. Learn more about the origins, distribution, and characteristics of …
Chemical substance - New World Encyclopedia
A chemical substance is any material that has a definite chemical composition. Moreover, a pure substance cannot be separated into other substances by any mechanical process. [2] Chemical elements and compounds are substances, mixtures are not.
Chemical compound - Wikipedia
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element is therefore not a compound.