Solid, in physics and chemistry, one of the three states of matter. The other two states of matter are gas and liquid. A solid tends to maintain its shape without a container. Some solids are harder than others. True solids are crystalline; that is, the atoms of which they are composed are arranged in definite, three-dimensional patterns. They have definite melting temperatures. Some substances, such as glass and tar, that appear to be solid are amorphous—they do not have a crystalline atomic structure. These substances soften and melt over a range of temperatures; they are not true solids.
Did anything vaguely scientific happen in the Middle Ages? Take this quiz to learn how we got through a dark period of history while trying to figure out how the sun was revolving around us, anyway.
Electronics, the branch of science and technology concerned with the nature, uses, and manufacture of devices in which electrons flow through a gas, vacuum, or semiconductor. Learn all about electronics.