If an object has mass, then it's made up of matter, a comprehensive name for the atoms and molecules that make up our entire world. We're able to describe matter as something that exists in states, which are also commonly called phases. While there are three states of matter that people are most familiar with, solids, liquids, and gases, there are two others that may not be that widely known but are also important. These are plasma and Bose-Einstein condensates.

Solids, liquids, and gases are the most easily observable phases of matter. In a solid, the particles are packed very tightly together. In a liquid, the particles can move about more easily. In a gas, they're even more spread out.

Particles in chemistry can be made up of either molecules, atoms, or ions. The actual physical aspects of the molecules, atoms, and ions are what decide the matter's state.

Solid

If an object can hold its shape and is very difficult to compress, it's usually referred to a solid. In a solid, you'll find a high density; the molecules are packed very closely together. If you look around you right now, you'll likely see a countless amount of things that would be considered solids, including the seat that you're sitting on and the walls nearby.

Liquid

In a liquid, the molecules are able to slide past each other, allowing the substance to flow. While a solid would be much more difficult to compress than a liquid, it doesn't necessarily mean that compressing a liquid is easy. Examples of liquids include water, milk, and gasoline.

Gas

The atoms within gases become a lot more spread out and will bump into one another. Compared to liquids and solids, gas is the easiest to compress. It will fill up any container, but the vapor can escape if the container isn't completely sealed. The air we breathe is a mix of gases including molecules that contain carbon, nitrogen, and oxygen.

Plasma

Plasma is a substance hotter than a gas that is able to carry an electric charge. It's a type of matter that comes into existence when atoms are energized enough to enter an excited state, splitting electrons from their nuclei and allowing them to move about freely. In this process, the electrons can increase in energy level, and as a result of that, they're able to give off light. The plasma particles move around in random patterns and are spread out.

Plasmas combine to make up 99% of our visible universe. On Earth, you can commonly find plasmas within neon signs and fluorescent lights. A much larger form of plasma is lightning. Auroras are also made from plasmas, created when atoms found within the plasma in the atmosphere interact with particles from outer space. But one of the most common forms of plasma is found in stars. In fact, the sun is made of plasma.

Bose-Einstein Condensate (BEC)

Having a complete understanding of Bose-Einstein condensates (BECs) requires knowing a thing or two about temperature. At absolute zero, around -273° C, all molecular motion stops: It's the coldest temperature possible. A BEC will form when the temperature is just above absolute zero, and it only forms within certain elements. As a BEC forms, the atoms will begin to clump together, and their energy levels overlap, becoming impossible to tell apart, essentially forming one super-atom.

Changes of State

To change the state of matter, energy must be added or removed. One of the simplest ways to explain this is to use water as an example. A block of ice is solid water. Adding heat melts the ice, turning it into liquid water. Continuing to add heat will turn the liquid water into steam, or water vapor, a gas. A gas is also able to transition into either a plasma or BEC if enough energy is applied to it (we see this in a plasma TV, where electricity is used to excite small pockets of gas, creating a glowing plasma). You can also reverse the process by removing energy, like when you remove heat from water by putting it in the freezer.

If you add enough heat to a substance all at once, you can also cause the process of sublimation, which is when a solid turns directly into a gas. You can see this with dry ice, which is frozen carbon dioxide: Room temperature is much hotter than the temperature at which carbon dioxide turns into a gas, so when dry ice is exposed to room temperature, it turns directly into a gas.

For more information on the states of matter, please visit the following helpful resources:

• Common Misconceptions About States and Changes of Matter and the Water Cycle
• The Various States of Matter
• Plasma: The Fourth State of Matter
• Q&A: What Is the State of Matter of a Flame?
• What Are the Properties of a Bose-Einstein Condensate?
• A Background on Mass, Weight, and Density
• The Problems With Classifying Solids, Liquids, and Gases
• What Makes a Solid a Solid?
• Which Is the State of Matter That Has a Definite Shape and Definite Volume?
• Hyperprecise Measurement With Bose Einstein-Condensates
• Bose Einstein-Condensates With Rubidium Atoms
• Density of Liquids in Different States