When determining the solid state of matter, it is important to note that there are five types of solids: covalent, ionic, metallic, molecular, and network. Each solid has its own special properties, usages, and chemical composition that distinguish it from the others.
Covalent solids are composed of atoms covalently bonded together. These atoms are either the same or different. The difference between these two is called its lattice structure.
Ionic solids consist of elements with ions combined into a single substance. These ions are either positively or negatively charged, and they are arranged in a lattice structure.
Metallic solids have atoms conjoined in a lattice structure with no chemical bonding between them. These atoms are usually the same kind, but some metallic solids have mixed atom types within the solid.
Network solids have molecules arranged in a repeating pattern with no chemical bonding between them. Like metallic solids, these molecules are usually of the same type.
Ice
The term ice refers to water in its solid state, also known as a crystalline substance. There are multiple types of ice, or frozen water, that can be studied and identified.
Water can exist in either a liquid or a solid state, depending on the temperature. As water temperatures drop below 4 degrees Celsius (39 Fahrenheit), it freezes into ice. This point at which it freezes is called its melting point.
There are several types of ice that can be classified by its structure. The two main classes of ice are covalent and ionic. Covalent ice is similar to diamond structure where molecules are stuck together via strong chemical bonds. Ionic ice has an arrangement similar to sodium chloride (salt) where molecules are surrounded by ions that hold them together.
Both of these structures prevent the melt of the solid due to the strong bonds within the crystal. The other types of solids listed may not possess this property and may melt at higher temperatures.
Sodium sulfate
Sodium sulfate, more commonly known as soap, is a common chemical produced in industrial processes. Soaps are classified as sodium ion compounds, meaning the compound contains the sodium ion.
Soaps are mixtures of alkali metals such as sodium or potassium with fats and oils. When introduced to water, these molecules separate, with the soap dissolving in the water and the fat or oil becoming a gel.
Sodium sulfate is a chemical containing the sodium ion and sulfuric acid. Like other soaps, it dissolves in water, but it does not contain any atoms besides sodium and sulfur.
These atoms form very tight bonds called covalent bonds. This makes sodium sulfate a covalent solid. It is also an inorganic compound, making it an metallic solid.
Copper chloride
A covalent solid is one in which the atoms are arranged in a lattice structure. The atoms are held together by electron interactions, also called covalent bonds.
In metals, the solid state is called the metallic solid. Metals are defined as a material that is composed of a substance of a single element, and whose characteristic physical properties are steel or iron-like.
The characteristic physical properties include being hard, having good thermal and electrical conductivity, and being malleable (can be shaped easily).
In nonmetals, the solid state is called the molecular solid. Nonmetals are defined as a material that is composed of two or more elements, with characteristic physical properties that are not steel or iron-like. An example of a molecular solid is water (H2O).
Both covalent and ionic solids can be either magnetic or nonmagnetic. Magnetic solids have atomic nuclei that contain internal magnetic fields which can line up with each other; when these nuclei are spread out, they repel each other and cause the material to be hard to compress.
Mercury(II) sulfate
A covalent solid is a solid formed when molecules are held together by strong chemical bonds. These bonds can be in the form of ionic or covalent links.
When atoms bond together to form a solid through covalent links, the molecule being formed is called a polymeric substance. In this case, the substance being formed is mercury sulfate.
Mercury sulfate is a special case of a covalent solid because it is also an ionic solid. An ionic solid is one where atoms are bonded together via strong chemical ions. In this case, the mercury and sulfur atoms bond together to form crystals through covalent links, but there are also strong chemical ions between these atoms.
Confusing? Try looking at it this way: Mercury sulfate is a crystal that is made up of both mercury and sulfur atoms that are bonded together via both covalent and ionic links.
Calcium carbonate
Calcium carbonate is a common mineral that is composed of calcium and carbon. Calcium carbonate is found in rocks such as limestone and marble.
Calcium carbonate is a binary compound, meaning it consists of two elements: calcium and carbon. Calcium carbonate is a type of solid called a bicovalent solid. This means it consists of two atoms per molecule, which are bonded together via a covalent bond.
Bicovalent solids can be classified as either ionic or molecular depending on how the atoms are bonded together. In the case of calcium carbonate, the molecules are very small so they are considered molecular.
Ionic solids have larger molecules that are positively or negatively charged depending on the type of atoms it contains. Molecular solids do not have charged atoms and have smaller molecules than ionic solids.
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is a white powder, which can be created by mixing potassium chloride and sodium nitrate.
Potassium nitrate is a salt, specifically a nitrogen-containing salt of potassium. Like all salts, it consists of Na+ and Cl− ions, in this case arranged in a lattice structure surrounding anions and cations of nitrogen.
Like most solids, potassium nitrate can assume a crystal structure. In the case of potassium nitrate, it is called the monoclinic system, which has seven distinct planes of atoms or molecules. These planes are defined by differences in orientation of atoms or molecules within the solid.
There are two special types of atoms or molecules in this solid: those that are perpendicular to all neighboring planes, and those that are symmetrical to only one neighboring plane.
Aluminum oxide
A very interesting property of solid aluminum oxide is that it can be changed from a solid into a liquid by intense heat. This process is called liquid phase transformation (LPT) and it occurs when the aluminum oxide crystal structure is broken down by heat, allowing the atoms to rearrange into a liquid structure.
When aluminum oxide is in a liquid state, it is called alumina liqium. It has several practical applications, including coating silicon wafers used in semiconductor and photovoltaic industries. When the alumina liquified, it can be sprayed onto a substrate to form a protective coating.
Alumina liquification can be done in two ways: through direct heating or indirect heating. In direct heating, the crystal structure of aluminum oxide is broken down by direct heat from flames or sparks. In indirect heating, the crystal structure of aluminum oxide is broken down by indirect heat transferred from another material.
Silicon dioxide
A common solid that is classified as both an ionic and a metallic solid is silicon dioxide, more commonly known as sand.
Sand is a mixture of silicon and oxygen atoms, which bond together in large groups called crystals. These crystals are structured in layers, similar to how a tree has layers of bark.
The silicon atoms are bound to many oxygen atoms, which are not part of the crystal structure. When these dissolve in water, they form what is called a solution. This makes it easy to wash off your hands or feet when standing in a pool or on the beach.
Ionic solids are held together by electric forces between oppositely charged ions. These bonds can be strong or weak, depending on the strength of the charge of the ion and how many there are.
Metallic solids have lattices of positively charged ions surrounded by negative electrons. When these lattices are put together, they form strong bonds between all of the elements.
