What makes solid

Ice keeps its shape when frozen, even if it is removed from its container. However, ice is different from most solids: its molecules are less densely packed than in liquid water. This is why ice floats. The simplest way to determine if something is a liquid is to ask this question: If I try and move it from one container to another i.

If you have a glass of water and pour it into another glass, it clearly conforms — it takes on the shape of the glass. If you spill the water, it will go everywhere. In most liquids, the particles are less densely packed, giving them the ability to move around and slide past each other.

While a liquid is easier to compress than a solid, it is still quite difficult — imagine trying to compress water in a confined container! Water is an example of a liquid, and so are milk, juice and lemonade. Find out more about water by looking at our wide range of resources under the water topic. The atoms and molecules in gases are much more spread out than in solids or liquids. They vibrate and move freely at high speeds.

A gas will fill any container, but if the container is not sealed, the gas will escape. Gas can be compressed much more easily than a liquid or solid. Think about a diving tank — L of gas is compressed into a 3 L cylinder. Right now, you are breathing in air — a mixture of gases containing many elements such as oxygen and nitrogen. Water vapour is the gaseous form or state of water.

Unlike ice or water, water vapour is invisible. We exhale water vapour whenever we breathe out. This means that a liquid is not definite in shape but rather conforms to the shape of its container. Its volume is usually greater than that of its corresponding solid water is a well-known exception to this rule. The highest temperature at which a particular liquid can exist is called its critical temperature. This process of a liquid changing to a gas is called evaporation. Gas molecules have either very weak bonds or no bonds at all, so they can move freely and quickly.

Because of this, not only will a gas conform to the shape of its container, it will also expand to completely fill the container. Gas molecules have enough kinetic energy that the effect of intermolecular forces is small or zero, for an ideal gas , and they are spaced very far apart from each other; the typical distance between neighboring molecules is much greater than the size of the molecules themselves.

A gas at a temperature below its critical temperature can also be called a vapor. A vapor can be liquefied through compression without cooling. It can also exist in equilibrium with a liquid or solid , in which case the gas pressure equals the vapor pressure of the liquid or solid. A supercritical fluid SCF is a gas whose temperature and pressure are greater than the critical temperature and critical pressure. In this state, the distinction between liquid and gas disappears. A supercritical fluid has the physical properties of a gas, but its high density lends it the properties of a solvent in some cases.

This can be useful in several applications. For example, supercritical carbon dioxide is used to extract caffeine in the manufacturing of decaffeinated coffee.

Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:. Molecular motion for the particles in a solid is confined to very small vibrations of the atoms around their fixed positions; therefore, solids have a fixed shape that is difficult to change. Solids also have a definite volume; that is, they keep their size no matter how you try to change them. Solids are divided into two main categories, crystalline solids and amorphous solids, based on how the particles are arranged.

Crystalline solids, or crystals, are regarded as "true solids. Common table salt is one example of this kind of solid. In crystalline solids, the atoms, ions or molecules are arranged in an ordered and symmetrical pattern that is repeated over the entire crystal. The smallest repeating structure of a solid is called a unit cell, which is like a brick in a wall.

Unit cells combine to form a network called a crystal lattice. There are 14 types of lattices, called Bravais lattices named after Auguste Bravais, a 19th-century French physicist , and they are classified into seven crystal systems based on the arrangement of the atoms.

The ChemWiki page at the University of California, Davis lists these systems as cubic, hexagonal, tetragonal, rhombohedral, orthorhombic, monoclinic and triclinic. Aside from the regular arrangement of particles, crystalline solids have several other characteristic properties. They are generally incompressible, meaning they cannot be compressed into smaller shapes. Because of the repeating geometric structure of the crystal, all the bonds between the particles have equal strength.

This means that a crystalline solid will have a distinct melting point, because applying heat will break all the bonds at the same time. Crystalline solids also exhibit anisotropy. This means that properties such as refractive index how much light bends when passing through the substance , conductivity how well it conducts electricity and tensile strength the force required to break it apart will vary depending on the direction from which a force is applied.

Crystalline solids also exhibit cleavage ; when broken apart, the pieces will have planed surfaces, or straight edges. There are four types of crystalline solids: ionic solids, molecular solids, network covalent solids and metallic solids.

Ionic compounds form crystals that are composed of oppositely charged ions: a positively charged cation and a negatively charged anion. Because of the strong attraction between opposite charges, it takes a lot of energy to overcome ionic bonds.