What are the common physical states of matter, and how do they differ from one another?

Solids are one of the most common states of matter we encounter every day, from the devices we use, to the ground we walk on. The defining characteristic of a solid is its structural rigidity. In this state, atoms, molecules, or ions are densely packed together, contributing to their fixed volume and definite shape. Imagine a cube or a sphere, these shapes remain the same regardless of the container they're in because the particles that make up these solids cannot move freely past each other; they are bounded by strong intermolecular forces. This stiffness leads to other properties such as maintaining a constant shape, resisting external forces, and atypical ability to be compressed.

However, it's important to note that not all solids are created equal. Their rigidity can vary; for example, some metals can be bent or hammered into sheets (a property known as malleability), or drawn into wires (ductility). Yet, these processes do not alter the volume of the metal; they simply rearrange the particles while maintaining overall solidarity.

Liquids are the go-between state of matter that display characteristics of both solids and gases. Unlike solids, liquids do not hold a definite shape but rather conform to the shape of their containers. This fluidity stems from the particles being less tightly packed than in solids, allowing them to slide past one another while still being attracted enough to not fly apart.

This sliding action gives rise to some very familiar phenomena: the ability of liquids to flow, something we can observe in water coursing through a stream or when pouring a drink. Liquids have a fixed volume like solids but adapt shape due to their weaker, yet significant, intermolecular forces. Other noteworthy properties of liquids include their varying viscosities—or thicknesses—and the fact that they are nearly incompressible, a trait they share with solids. Additionally, surface tension—the responsible force for the beading up of water droplets on a surface—is a unique property of the liquid state.

Gases are the state of matter that are all around us, even if we can't see them; the air we breathe is a prime example. They are composed of particles that are far apart compared to those in solids and liquids, and thus, have neither a fixed volume nor a definite shape—their shape and volume are determined by the container they occupy. Particles in a gas move rapidly in all directions and are in a state of constant motion.

One of the most intriguing aspects of gases is their compressibility. Unlike solids and liquids, you can squeeze a gas into a smaller volume by applying pressure, a principle that's applied in myriad everyday applications, such as the air in our car tires. Additionally, gases diffuse quickly, mixing with other gases in an open environment. This mixing is why if you spray perfume in one corner of a room, it doesn't take long before you can smell it in another corner. Temperature changes significantly affect gases; when heated, their particles move faster and can expand—a property known as thermal expansion.