Solid-state chemistry facts for kids

Solid-state chemistry, also called materials chemistry, is a branch of chemistry. It studies how solid materials are made, what they are made of, and how they behave. It looks at solids that aren't made of individual molecules.

This field is closely related to other sciences. These include solid-state physics, which studies how solids work, and materials science, which focuses on creating new materials. A big part of solid-state chemistry is making new materials and then figuring out what they are like.

History of Solid-State Chemistry

Solid-state chemistry has grown a lot thanks to new technology. It helps create materials used in everyday products and industries. Scientists in this field work for companies and also explore new ideas in universities.

Important discoveries in the 1900s include special materials like zeolites. These were used as catalysts in the 1950s to process petroleum. In the 1960s, very pure silicon became key for microelectronic devices. Then, in the 1980s, "high temperature" superconductivity was discovered.

William Lawrence Bragg invented X-ray crystallography in the early 1900s. This tool helped scientists make many more discoveries about solids.

Carl Wagner is sometimes called the "father of solid-state chemistry." He studied how reactions happen at the atomic level inside solids. His work helped us understand how atoms move and change in solid materials.

How Solid Materials Are Made

Chemists use many different ways to make solid materials. For some materials, like those used in organic chemistry, methods are similar to making organic compounds. These often happen at room temperature. Sometimes, redox reactions are done using electricity.

Using High Heat (Oven Techniques)

Many solid materials need high heat to form. Chemists often use special ovens called tube furnaces. These can heat materials up to about 1,100°C (2,012°F). For even higher temperatures, up to 2,000°C (3,632°F), special ovens with electric heating elements are used.

High temperatures are often needed to make the starting materials mix and react. However, some solid reactions can happen at lower temperatures, like 100°C (212°F).

Melting and Cooling Methods

One way to make solids is to melt the starting materials together. After they melt, they are cooled down to become solid again. Sometimes, the solid is then heated slowly in a process called annealing. This helps the atoms arrange themselves correctly.

If the materials can easily turn into gas (volatile materials), they are often put into a sealed glass tube called an ampoule. All the air is removed from the ampoule. The tube is often kept cold while being sealed. Then, the sealed ampoule is heated in an oven for a specific time.

Using Liquids (Solution Methods)

Solvents (liquids that dissolve other substances) can be used to make solids. This can happen by precipitation, where the solid forms out of the liquid. Or it can happen by evaporation, where the liquid dries up, leaving the solid behind.

Sometimes, the solvent is used under high pressure and at temperatures above its normal boiling point. This is called a hydrothermal method. Another method, called a flux method, adds a salt with a low melting point. This salt acts like a high-temperature solvent, helping the reaction happen.

Reactions with Gases

Many solids react easily with gases like chlorine, iodine, or oxygen. Other solids can combine with gases like carbon monoxide or ethylene. These reactions often happen in a tube where the gas flows over the solid.

A special type of gas reaction is a chemical transport reaction. A small amount of a "transport agent" (like iodine) is added to a sealed tube. The tube is then heated in an oven with different temperature zones. This method can help grow large, single crystals. These crystals are good for studying their structure using X-ray diffraction.

Chemical vapor deposition (CVD) is another common high-temperature method. It uses gases to create thin coatings or semiconductors.

Materials Sensitive to Air and Water

Many solids can absorb water from the air (hygroscopic) or react with oxygen. For example, many halides absorb water. To study them in their pure, dry form, chemists must handle them in a special sealed box called a glove box. This box is filled with dry gas, usually nitrogen, to keep out water and oxygen.

Studying Solid Materials

When chemists make a new solid material, they need to figure out what it is. They try changing the amounts of starting materials to see what new compounds or mixtures they can create.

Finding New Materials and Structures

One main way to study new solid materials is using powder diffraction. This is because many solid reactions create powders or solid blocks made of many tiny crystals. Powder diffraction helps identify known materials in the mixture. If a new pattern is found, chemists try to figure out its crystal structure.

Once the basic structure of a new material is known, the next step is to find the exact ratio of the elements in it (stoichiometry). Sometimes, the starting mixture gives a clue, especially if only one product forms. But this is not always the case.

Chemists often work hard to make a pure sample of the new material. If they can separate it, they can use methods like elemental analysis. They can also use a Scanning electron microscope (SEM) to look at the material and find out what elements are present. The easiest way to find the structure is by using single crystal X-ray diffraction.

Chemists also study which materials are stable at different compositions and temperatures. They create "phase diagrams" that show these relationships. Tools like thermal analysis (DSC or DTA) and temperature-dependent powder diffraction help them do this. This knowledge helps them improve how they make new materials. New materials are also described by their melting points and how much their composition can vary.

Other Ways to Study Solids

New solid materials are often studied using different methods from solid-state physics.

Optical Properties

For materials that are not metals, chemists look at how they interact with light. They use ultra-violet/visible light to get spectra. For semiconductors, this can tell them about the band gap, which affects how the material conducts electricity.

Electrical Properties

Chemists use methods like the four-point probe to measure how well a material conducts electricity (resistivity). They also measure the Hall effect. This helps them know if the material is an insulator (doesn't conduct), a semiconductor (conducts a little), or a metal (conducts well). It also gives clues about how the atoms are bonded together.

Magnetic Properties

The magnetic properties of a material can be measured as its temperature changes. This helps determine if it is a paramagnet, ferromagnet, or antiferromagnet. This information also tells us about the chemical bonding inside the material. This is very important for materials containing transition metals. If a material has magnetic order, neutron diffraction can be used to find its magnetic structure.

Images for kids

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  Silicon wafers are used in electronic devices.

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  A tube furnace is used to heat materials during chemical reactions.

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  A chemical vapor deposition (CVD) reaction chamber.

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  A Scanning Electron Microscope (SEM) helps scientists see tiny details of materials.

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  An X-ray diffractometer (XRD) is used to study the structure of solid materials.

See also

In Spanish: Química del estado sólido para niños