Shop Windows to the Universe

Young Voices for the Planet DVD in our online store includes 8 films where students speak out and take action on climate change.
These crystals of the mineral pyrite are a good example of a solid.
Click on image for full size
Courtesy of Corel

Solid

Solid is one of the four common states of matter. The three others are gas, liquid, and plasma. There are also some other exotic states of matter that have been discovered in recent years.

Unlike liquids and gases, solids have definite shapes. If you pour some milk into a glass or fill a balloon with helium, the liquid (milk) or gas (helium) takes on the shape of the container (the glass or balloon). A solid keeps its own shape.

The atoms or molecules in a solid are packed together much more tightly in a solid than in a gas or a liquid. The atoms or molecules in a solid have fixed positions; they don't move around like atoms or molecules in a gas or liquid do. That's why liquids and gases can flow, but solids don't.

Solids are usually much more dense than liquids and gases, but not always. Mercury, a metallic element that is a liquid at room temperature, is denser than many solids. Aerogel, a very unusual human-made solid, is about 500 times less dense than water.

Many solid materials will melt when heated. When solids melt, they become liquids. For example, when iron is heated to a temperature around 1,538 C. (2,800 F.) it melts and becomes molten iron. When liquids are cooled they can freeze and become solids. A familiar example is liquid water turning into ice. Under certain conditions (usually low pressure) some solids can turn directly into a gas without first melting and becoming a liquid. When a solid turns directly into a gas we call the change "sublimation". Maybe you have seen dry ice (which is very cold, frozen carbon dioxide) sublimate.

Crystals, wood, rocks, most metals, and glass are all examples of common solids. Your bones and teeth are also solid materials. That's a good thing... it would be hard for you to eat or get around if it weren't for solids!

Last modified June 25, 2008 by Randy Russell.

Shop Windows to the Universe Science Store!

Our online store includes issues of NESTA's quarterly journal, The Earth Scientist, full of classroom activities on different topics in Earth and space science, as well as books on science education!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

The Plasma State

Plasma is known as the fourth state of matter (the first three states being solid, liquid and gas).Matter in ordinary conditions on Earth has electrons that orbit around the atomic nucleus. The electrons...more

Molecules

Most things around us are made of groups of atoms bonded together into packages called molecules. The atoms in a molecule are held together because they share or exchange electrons. Molecules are made...more

Density Definition Page

Density is a measure of how much mass is contained in a given unit volume (density = mass/volume). It is usually expressed in kg/m^3, so you would say that a cube 2 meters on each side with a mass of 16...more

The Periodic Table of the Elements

Everything you see around you is made of tiny particles called atoms, but not all atoms are the same. Different combinations of protons , neutrons and electrons make different types of atoms and these...more

Changes of State: Solids, Liquids, and Gases

Any substance, called matter, can exist as a solid material, liquid, or gas. These three different forms are called states. Matter can change its state when heated. As a solid, matter has a fixed volume...more

Carbon Dioxide - CO2

Carbon dioxide is a colorless and non-flammable gas at normal temperature and pressure. Although much less abundant than nitrogen and oxygen in Earth's atmosphere, carbon dioxide is an important constituent...more

Metals, Nonmetals, & Metalloids

The periodic table on the left separates the elements into three groups: the metals (green in the table), nonmetals (orange), and metalloids (blue). Most elements are metals. They are typically shiny,...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF