March 12, 2013

What is a Solid?

Hi, my name is Emerald Robinson, and in this “What Is” video, we’re going to investigate the state of matter called a “solid.”

Solids are materials that keep their form; that is, solids don’t change their shape or expand to fit the container that they are in.

Although there are many different solids, there are a few characteristics that they have in common.

First, the particles in a solid are arranged so that they remain close to one another. But this does not mean that there is no movement at all. Electrons still orbit the atoms’ nucleuses, and the atoms themselves vibrate or “jiggle,” but the molecules in a solid always stay in close proximity.

Second, solids can’t be compressed. Because there’s not a lot of space between the atoms, they can’t be squeezed together any closer than they already are. Sometimes scientists say that solids are a “condensed phase” of matter.

Third, in general, solids have melting and boiling points that are higher than room temperature.

Solids are sometimes classified by how their atoms are arranged. If the atoms in a substance are in a pattern, the solid is known as a crystal. Common crystals include metals, ceramics, and diamonds, which are large single crystals.

If the atoms in a substance are not arranged in a pattern, the solid is called “amorphous,” which means “without a form.” Common amorphic solids include plastics and glass.

Most of the time, solids are not made of all of one kind of atom – or even made consistently of the same material. These types of solids are called mixtures, or more scientifically, “composites.” Most of the things we see every day are composites, especially things in nature like rocks, wood, and soil.

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