<h2>Three Main Domains</h2>
Chemists study and describe the behavior of matter and <a data-lesson="energy" data-subject="chemistry" data-tutorial="thermochemistry" href="https://app.ulearngo.com/chemistry/thermochemistry/energy">energy</a> in three different domains: macroscopic, microscopic, and symbolic. These domains provide different ways of considering and describing chemical behavior.
Macro is a Greek word that means “large.” The macroscopic domain is familiar to us: It is the realm of everyday things that are large enough to be sensed directly by human sight or touch. In daily life, this includes the food you eat and the breeze you feel on your face. The macroscopic domain includes everyday and laboratory chemistry, where we observe and measure <a data-lesson="physical-chemical-properties" data-subject="chemistry" data-tutorial="chemistry-essential-ideas" href="https://app.ulearngo.com/chemistry/chemistry-essential-ideas/physical-chemical-properties">physical</a> and chemical properties, or changes such as density, solubility, and flammability.
The microscopic domain of chemistry is almost always visited in the imagination. Micro also comes from Greek and means “small.” Some aspects of the microscopic domains are visible through a microscope, such as a magnified image of graphite or bacteria. Viruses, for instance, are too small to be seen with the naked eye, but when we’re suffering from a cold, we’re reminded of how real they are.
However, most of the subjects in the microscopic domain of chemistry—such as <a data-lesson="chemical-formulas" data-subject="chemistry" data-tutorial="atoms-molecules-ions" href="https://app.ulearngo.com/chemistry/atoms-molecules-ions/chemical-formulas">atoms</a> and molecules—are too small to be seen even with standard microscopes and often must be pictured in the mind. Other components of the microscopic domain include ions and electrons, protons and neutrons, and chemical bonds, each of which is far too small to see.
This domain includes the individual metal atoms in a wire, the ions that compose a <a data-lesson="acid-base-reactions-continued-2" data-subject="chemistry" data-tutorial="acid-base-redox-reactions" href="https://app.ulearngo.com/chemistry/acid-base-redox-reactions/acid-base-reactions-continued-2">salt</a> crystal, the changes in individual molecules that result in a color change, the conversion of nutrient molecules into tissue and energy, and the evolution of <a data-lesson="calorimetry" data-subject="chemistry" data-tutorial="thermochemistry" href="https://app.ulearngo.com/chemistry/thermochemistry/calorimetry">heat</a> as bonds that hold atoms together are created.
The symbolic domain contains the specialized language used to represent components of the macroscopic and microscopic domains. Chemical symbols (such as those used in the periodic table), chemical formulas, and <a data-lesson="chemical-equations" data-subject="chemistry" data-tutorial="chemical-reactions-stoichiometry" href="https://app.ulearngo.com/chemistry/chemical-reactions-stoichiometry/chemical-equations">chemical equations</a> are part of the symbolic domain, as are <a data-lesson="graphs-and-le-chateliers-principle" data-subject="chemistry" data-tutorial="chemical-equilibrium" href="https://app.ulearngo.com/chemistry/chemical-equilibrium/graphs-and-le-chateliers-principle">graphs</a> and drawings. We can also consider calculations as part of the symbolic domain.
These symbols play an important role in chemistry because they help interpret the behavior of the macroscopic domain in terms of the components of the microscopic domain.
One of the challenges for students learning chemistry is recognizing that the same symbols can represent different things in the macroscopic and microscopic domains, and one of the features that makes chemistry fascinating is the use of a domain that must be imagined to explain behavior in a domain that can be observed.
<div class="wp-caption alignnone" id="attachment_96098" style="width: 800px"><a href="https://data.ulearngo.com/assets/ecf61f93-75f1-44a8-a1f7-69d62086dc16"><img alt="water-chemistry-domains" class="size-full wp-image-96098" height="442" src="https://data.ulearngo.com/assets/ecf61f93-75f1-44a8-a1f7-69d62086dc16" width="800"/></a>(a) Moisture in the air, icebergs, and the ocean represent water in the macroscopic domain. (b) At the molecular level (microscopic domain), gas molecules are far apart and disorganized, solid water molecules are close together and organized, and liquid molecules are close together and disorganized. (c) The formula H2O symbolizes water, and (g), (s), and (l) symbolize its phases. Note that clouds are actually comprised of either very small liquid water droplets or solid water crystals; gaseous water in our atmosphere is not visible to the naked eye, although it may be sensed as humidity. Image credit:- a: Modification of work by “Gorkaazk”/Wikimedia Commons; b and c: OpenStax, Chemistry</div>
A helpful way to understand the three domains is via the essential and ubiquitous substance of water. That water is a liquid at moderate temperatures, will freeze to form a solid at lower temperatures, and boil to form a gas at higher temperatures (<a href="#attachment_96098">see image above</a>) are macroscopic observations.
But some properties of water fall into the microscopic domain—what we cannot observe with the naked eye. The description of water as comprised of two <a data-lesson="hydrogen-reactions" data-subject="chemistry" data-tutorial="metals-metalloids-nonmetals" href="https://app.ulearngo.com/chemistry/metals-metalloids-nonmetals/hydrogen-reactions">hydrogen</a> atoms and one <a data-lesson="occurrence-preparation-and-compounds-of-oxygen" data-subject="chemistry" data-tutorial="metals-metalloids-nonmetals" href="https://app.ulearngo.com/chemistry/metals-metalloids-nonmetals/occurrence-preparation-and-compounds-of-oxygen">oxygen</a> atom, and the explanation of freezing and boiling in terms of attractions between these molecules, is within the microscopic arena.
The formula H2O, which can describe water at either the macroscopic or microscopic levels, is an example of the symbolic domain. The abbreviations (g) for gas, (s) for solid, and (l) for liquid are also symbolic.

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Domains of Chemistry

Chemistry generally explores the substances of which matter is composed, the investigation of their properties and reactions, and the use of such reactions to form new substances. 

Chemistry

Explore the essential ideas in chemistry, including the scientific method, laboratory skills and safety, states of matter, measurement uncertainty, models of the atom, electronic configurations, and more.


Domains of Chemistry

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