I'm gaining more. Plasma! Caramelization!

<h2>Classifying Matter</h2>
<h3>Pure Substances</h3>
<p id="fs-idm27277840">We can classify matter into several categories. Two broad categories are <a data-lesson="mixtures" data-subject="chemistry" data-tutorial="classification-of-matter" href="https://app.ulearngo.com/chemistry/classification-of-matter/mixtures">mixtures</a> and pure substances. A <strong>pure substance</strong> has a constant composition. All specimens of a pure substance have exactly the same makeup and properties. Any sample of sucrose (table sugar) consists of 42.1% carbon, 6.5% hydrogen, and 51.4% oxygen by mass. Any sample of sucrose also has the same <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> properties, such as melting point, color, and sweetness, regardless of the source from which it is isolated.</p>
<h3>Elements and Compounds</h3>
<p id="fs-idm96243408">We can divide <a data-lesson="pure-substances" data-subject="chemistry" data-tutorial="classification-of-matter" href="https://app.ulearngo.com/chemistry/classification-of-matter/pure-substances">pure substances</a> into two classes: elements and compounds. Pure substances that cannot be broken down into simpler substances by chemical changes are called <strong>elements</strong>. Iron, silver, gold, aluminum, sulfur, oxygen, and <a data-lesson="isolation-of-copper" data-subject="chemistry" data-tutorial="transition-metals" href="https://app.ulearngo.com/chemistry/transition-metals/isolation-of-copper">copper</a> are familiar examples of the more than 100 known elements, of which about 90 occur naturally on the earth, and two dozen or so have been created in laboratories.</p>
<div class="wp-caption alignnone" id="attachment_96108" style="width: 800px"><a href="https://data.ulearngo.com/assets/c58ab49b-25eb-47f2-b287-0d968dcd339d"><img alt="mecury-II-oxide" class="size-full wp-image-96108" height="241" src="https://data.ulearngo.com/assets/c58ab49b-25eb-47f2-b287-0d968dcd339d" width="800"/></a><p class="wp-caption-text">(a) The compound mercury(II) oxide, (b) when heated, (c) decomposes into silvery droplets of liquid mercury and invisible oxygen gas. Image credit: modification of work by Paul Flowers</p></div>
<p>Pure substances that can be broken down by chemical changes are called <strong>compounds</strong>. This breakdown may produce either elements or other compounds, or both. Mercury (II) oxide, an orange, crystalline solid, can be broken down by heat into the elements mercury and oxygen (see image above). You can also watch the video below by North Carolina School of Science and Mathematics (NCSSM) to see the breakdown of mercury (II) oxide.</p>
<p><iframe allowfullscreen="allowfullscreen" frameborder="0" height="360" src="https://www.youtube.com/embed/_Y1alDuXm6A?rel=0&amp;modestbranding=1&amp;cc_lang_pref=en&amp;cc_load_policy=1" width="640"></iframe></p>
<p>When heated in the absence of air, the compound sucrose is broken down into the element <a data-lesson="carbon" data-subject="chemistry" data-tutorial="metals-metalloids-nonmetals" href="https://app.ulearngo.com/chemistry/metals-metalloids-nonmetals/carbon">carbon</a> and the compound water. (The initial stage of this process, when the sugar is turning brown, is known as caramelization—this is what imparts the characteristic sweet and nutty flavor to caramel apples, caramelized onions, and caramel).</p>
<p>Silver (I) chloride is a white solid that can be broken down into its elements, silver and chlorine, by absorption of light. This property is the basis for the use of this compound in photographic films and photochromic eyeglasses (those with lenses that darken when exposed to light). You can also watch the video below by Dr Peter Wothers, ‎University of Cambridge to see an example of the photochemical decomposition of silver chloride (AgCl), the basis of early photography.</p>
<p><iframe allowfullscreen="allowfullscreen" frameborder="0" height="360" src="https://www.youtube.com/embed/ZLEYyzW427I?rel=0&amp;modestbranding=1&amp;cc_lang_pref=en&amp;cc_load_policy=1" width="640"></iframe></p>
<p id="fs-idm50488272">The properties of combined elements are different from those in the free, or uncombined, state. For example, white crystalline sugar (sucrose) is a compound resulting from the chemical combination of the element carbon, which is a black solid in one of its uncombined forms, and the two elements hydrogen and oxygen, which are colorless <a data-lesson="introducing-gases" data-subject="chemistry" data-tutorial="gases" href="https://app.ulearngo.com/chemistry/gases/introducing-gases">gases</a> when uncombined.</p>
<p>Free sodium, an element that is a soft, shiny, metallic solid, and free chlorine, an element that is a yellow-green gas, combine to form <a data-lesson="redox-reactions" data-subject="chemistry" data-tutorial="reactions-in-aqueous-solution" href="https://app.ulearngo.com/chemistry/reactions-in-aqueous-solution/redox-reactions">sodium</a> chloride (table salt), a compound that is a white, crystalline solid.</p>
<p>When talking about the classification of matter, we cannot conclude our discussion without looking at mixtures. In the next lesson, we will look at mixtures.</p>

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Classification of Matter

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.


Classification of Matter

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