The smallest component of an element having the chemical properties of the element, consisting of a nucleus containing combinations of neutrons and protons and one or more electrons bound to the nucleus by electrical attraction; the number of protons determines the identity of the element.
The gaseous envelope surrounding the earth; the air.
A substance that causes or accelerates a chemical reaction without itself being affected.
a pure substance composed of two or more elements whose composition is constant.
a representation of a substance using symbols for its constituent elements
Material produced by or used in a reaction involving changes in atoms or molecules
1. The act or process of reducing a gas or vapor to a liquid or solid form.
2. Chemistry. a reaction between two or more organic molecules leading to the formation of a larger molecule and the elimination of a simple molecule such as water or alcohol.
One of a class of substances that cannot be separated into simpler substances by chemical means. See also chart under periodic table.
To draw moisture from, as by heating, leaving only the dry solid portion.
A metric unit of mass equal to one thousandth of a kilogram
the force of attraction by which terrestrial bodies tend to fall toward the center of the earth.
Anything that has mass or takes up space.
The chemical processes occurring within a living cell or organism that are necessary for the maintenance of life. In metabolism some substances are broken down to yield energy for vital processes while other substances, necessary for life, are synthesized.
An aggregate of two or more substances that are not chemically united and that exist in no fixed proportion to each other.
The smallest physical unit of an element or compound, consisting of one or more like atoms in an element and two or more different atoms in a compound.
One of the extremely small constituents of matter, as an atom or nucleus.
Any process involving a substance's change from one state (gas, liquid, solid) to another without alteration of the chemical composition.
The plant or animal tissue rich in such molecules, considered as a food source supplying essential amino acids to the body.
In chemistry, the direct conversion of a solid into a gas, without passage through a liquid stage.
The amount of space an object occupies