{"id":32,"date":"2016-01-11T19:58:30","date_gmt":"2016-01-11T19:58:30","guid":{"rendered":"https:\/\/opentextbc.ca\/introductorychemistryclone\/chapter\/some-basic-definitions-2\/"},"modified":"2020-05-05T17:48:05","modified_gmt":"2020-05-05T17:48:05","slug":"some-basic-definitions","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/introductorychemistryclone\/chapter\/some-basic-definitions\/","title":{"raw":"Some Basic Definitions","rendered":"Some Basic Definitions"},"content":{"raw":"
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Learning Objectives<\/p>\r\n\r\n<\/header>\r\n

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  1. Learn the basic terms used to describe matter.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\nThe definition of chemistry\u2014the study of the interactions of matter with other matter and with energy\u2014uses some terms that should also be defined. We start the study of chemistry by defining some basic terms.\r\n\r\n[pb_glossary id=\"1120\"]Matter[\/pb_glossary].\u00a0A book is matter, a computer is matter, food is matter, and dirt in the ground is matter. Sometimes matter may be difficult to identify. For example, air is matter, but because it is so thin compared to other matter (e.g., a book, a computer, food, and dirt), we sometimes forget that air has mass and takes up space. Things that are not matter include thoughts, ideas, emotions, and hopes.\r\n
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    Example 1.1<\/p>\r\n\r\n<\/header>\r\n

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    Problems<\/h1>\r\nWhich of the following is matter and not matter?\r\n
      \r\n \t
    1. a hot dog<\/li>\r\n \t
    2. love<\/li>\r\n \t
    3. a tree<\/li>\r\n<\/ol>\r\n

      Solutions<\/h2>\r\n
        \r\n \t
      1. A hot dog has mass and takes up space, so it is matter.<\/li>\r\n \t
      2. Love is an emotion, and emotions are not matter.<\/li>\r\n \t
      3. A tree has mass and takes up space, so it is matter.<\/li>\r\n<\/ol>\r\n

        Test Yourself<\/h1>\r\nWhich of the following is matter and not matter?\r\n
          \r\n \t
        1. the moon<\/li>\r\n \t
        2. an idea for a new invention<\/li>\r\n<\/ol>\r\n

          Answers<\/h2>\r\n
            \r\n \t
          1. The moon is matter.<\/li>\r\n \t
          2. The invention itself may be matter, but the idea for it is not.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n\r\n[caption id=\"attachment_24\" align=\"aligncenter\" width=\"300\"]\"Ice<\/a> Figure 1.1 \"The Phases of Matter.\" Chemistry recognizes three fundamental phases of matter: solid (left), liquid (middle), and gas (right).[\/caption]\r\n\r\nTo understand matter and how it changes, we need to be able to describe matter. There are two basic ways to describe matter: physical properties and chemical properties. [pb_glossary id=\"1142\"]Physical properties[\/pb_glossary] are characteristics that describe matter as it exists. Some of many physical characteristics of matter are shape, color, size, and temperature. An important physical property is the [pb_glossary id=\"1127\"]phase[\/pb_glossary] (or state) of matter. The three fundamental phases of matter are solid, liquid, and gas (see Figure 1.1 \"The Phases of Matter\"<\/a>).\r\n\r\n[caption id=\"attachment_25\" align=\"aligncenter\" width=\"300\"]\"A<\/a> Figure 1.2 \"Chemical Properties.\" The fact that this match burns is a chemical property of the match.[\/caption]\r\n\r\n[pb_glossary id=\"1143\"]Chemical properties[\/pb_glossary]\u00a0are characteristics of matter that describe how matter changes form in the presence of other matter. Does a sample of matter burn? Burning is a chemical property. Does it behave violently when put in water? This reaction is a chemical property as well (Figure 1.2 \"Chemical Properties\"<\/a>). In the following chapters, we will see how descriptions of physical and chemical properties are important aspects of chemistry.\r\n
            \r\n
            \r\n\r\n[caption id=\"attachment_26\" align=\"aligncenter\" width=\"300\"]\"Ice<\/a> Figure 1.3 \"Physical Changes.\" The solid ice melts into liquid water\u2014a physical change.[\/caption]\r\n\r\n<\/div>\r\n<\/div>\r\nIf matter always stayed the same, chemistry would be rather boring. Fortunately, a major part of chemistry involves change. A [pb_glossary id=\"1144\"]physical change[\/pb_glossary]\u00a0occurs when a sample of matter changes one or more of its physical properties. For example, a solid may melt (Figure 1.3 \"Physical Changes\"<\/a>), or alcohol in a thermometer may change volume as the temperature changes. A physical change does not affect the chemical composition of matter. A [pb_glossary id=\"1145\"]chemical change[\/pb_glossary]\u00a0is the process of demonstrating a chemical property, such as the burning match in Figure 1.2 \"Chemical Properties\"<\/a>. As the matter in the match burns, its chemical composition changes, and new forms of matter with new physical properties are created. Note that chemical changes are frequently accompanied by physical changes, as the new matter will likely have different physical properties from the original matter.\r\n
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            Example 1.2<\/p>\r\n\r\n<\/header>\r\n

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            Problems<\/h1>\r\nDescribe each process as a physical change or a chemical change.\r\n
              \r\n \t
            1. Water in the air turns into snow.<\/li>\r\n \t
            2. A person\u2019s hair is cut.<\/li>\r\n \t
            3. Bread dough becomes fresh bread in an oven.<\/li>\r\n<\/ol>\r\n

              Solutions<\/h2>\r\n
                \r\n \t
              1. Because the water is going from a gas phase to a solid phase, this is a physical change.<\/li>\r\n \t
              2. Your long hair is being shortened. This is a physical change.<\/li>\r\n \t
              3. Because of the oven\u2019s temperature, chemical changes are occurring in the bread dough to make fresh bread. These are chemical changes. (In fact, a lot of cooking involves chemical changes.)<\/li>\r\n<\/ol>\r\n

                Test Yourself<\/h1>\r\nIdentify each process as a physical change or a chemical change.\r\n
                  \r\n \t
                1. A fire is raging in a fireplace.<\/li>\r\n \t
                2. Water is warmed to make a cup of coffee.<\/li>\r\n<\/ol>\r\n

                  Answers<\/h2>\r\n
                    \r\n \t
                  1. chemical change<\/li>\r\n \t
                  2. physical change<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\nA sample of matter that has the same physical and chemical properties throughout is called a [pb_glossary id=\"1146\"]substance[\/pb_glossary]. Sometimes the phrase pure substance<\/em> is used, but the word pure<\/em> isn\u2019t needed. The definition of the term substance is an example of how chemistry has a specific definition for a word that is used in everyday language with a different, vaguer definition. Here, we will use the term substance with its strict chemical definition.\r\n\r\nChemistry recognizes two different types of substances: elements and compounds. An [pb_glossary id=\"1147\"]element[\/pb_glossary]\u00a0is the simplest type of chemical substance; it cannot be broken down into simpler chemical substances by ordinary chemical means. There are about 115 elements known to science, of which 80 are stable. (The other elements are radioactive, a condition we will consider in Chapter 15 \"Nuclear Chemistry\"<\/a>.) Each element has its own unique set of physical and chemical properties. Examples of elements include iron, carbon, and gold.\r\n\r\nA [pb_glossary id=\"1148\"]compound[\/pb_glossary]\u00a0is a combination of more than one element. The physical and chemical properties of a compound are different from the physical and chemical properties of its constituent elements; that is, it behaves as a completely different substance. There are over 50 million compounds known, and more are being discovered daily. Examples of compounds include water, penicillin, and sodium chloride (the chemical name for common table salt).\r\n\r\nElements and compounds are not the only ways in which matter can be present. We frequently encounter objects that are physical combinations of more than one element or compound. Physical combinations of more than one substance are called [pb_glossary id=\"1149\"]mixtures[\/pb_glossary]. There are two types of mixtures. A [pb_glossary id=\"1150\"]heterogeneous mixture[\/pb_glossary]\u00a0is a mixture composed of two or more substances. It is easy to tell, sometimes by the naked eye, that more than one substance is present. A [pb_glossary id=\"1151\"]homogeneous mixture[\/pb_glossary]\u00a0is a combination of two or more substances that is so intimately mixed that the mixture behaves as a single substance. Another word for a homogeneous mixture is [pb_glossary id=\"1151\"]solution[\/pb_glossary]. Thus, a combination of salt and steel wool is a heterogeneous mixture because it is easy to see which particles of the matter are salt crystals and which are steel wool. On the other hand, if you take salt crystals and dissolve them in water, it is very difficult to tell that you have more than one substance present just by looking\u2014even if you use a powerful microscope. The salt dissolved in water is a homogeneous mixture, or a solution (Figure 1.4 \"Types of Mixtures\"<\/a>).\r\n\r\n[caption id=\"attachment_27\" align=\"aligncenter\" width=\"300\"]\"Flour<\/a> Figure 1.4 \"Types of Mixtures.\" On the left, the combination of two substances is a heterogeneous mixture because the particles of the two components look different. On the right, the salt crystals have dissolved in the water so finely that you cannot tell that salt is present. The homogeneous mixture appears like a single substance.[\/caption]\r\n\r\n
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                    Example 1.3<\/p>\r\n\r\n<\/header>\r\n

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                    Problems<\/h1>\r\nIdentify the following combinations as heterogeneous mixtures or homogenous mixtures.\r\n
                      \r\n \t
                    1. soda water (Carbon dioxide is dissolved in water.)<\/li>\r\n \t
                    2. a mixture of iron metal filings and sulfur powder (Both iron and sulfur are elements.)<\/li>\r\n<\/ol>\r\n

                      Solutions<\/h2>\r\n
                        \r\n \t
                      1. Because carbon dioxide is dissolved in water, we can infer from the behaviour of salt crystals dissolved in water that carbon dioxide dissolved in water is (also) a homogeneous mixture.<\/li>\r\n \t
                      2. Assuming that the iron and sulfur are simply mixed together, it should be easy to see what is iron and what is sulfur, so this is a heterogeneous mixture.<\/li>\r\n<\/ol>\r\n

                        Test Yourself<\/h1>\r\nAre the following combinations homogeneous mixtures or heterogeneous mixtures?\r\n
                          \r\n \t
                        1. the human body<\/li>\r\n \t
                        2. an amalgam, a combination of some other metals dissolved in a small amount of mercury<\/li>\r\n<\/ol>\r\n

                          Answers<\/h2>\r\n
                            \r\n \t
                          1. heterogeneous mixture<\/li>\r\n \t
                          2. homogeneous mixture<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\nThere are other descriptors that we can use to describe matter, especially elements. We can usually divide elements into metals and nonmetals, and each set shares certain (but not always all) properties. A [pb_glossary id=\"1152\"]metal[\/pb_glossary]\u00a0is an element that is solid at room temperature (although mercury is a well-known exception), is shiny and silvery, conducts electricity and heat well, can be pounded into thin sheets (a property called malleability<\/em>), and can be drawn into thin wires (a property called ductility<\/em>). A [pb_glossary id=\"1153\"]nonmetal[\/pb_glossary]\u00a0is an element that is brittle when solid, does not conduct electricity or heat very well, and cannot be made into thin sheets or wires (Figure 1.5 \"Semimetals\"<\/a>). Nonmetals also exist in a variety of phases and colors at room temperature. Some elements have properties of both metals and nonmetals and are called [pb_glossary id=\"1154\"]semimetals[\/pb_glossary] (or metalloids). We will see later how these descriptions can be assigned rather easily to various elements.\r\n\r\n[caption id=\"attachment_28\" align=\"aligncenter\" width=\"300\"]\"Liquid<\/a> Figure 1.5 \"Semimetals.\" On the left is some elemental mercury, the only metal that exists as a liquid at room temperature. It has all the other expected properties of a metal. On the right, elemental sulfur is a yellow nonmetal that usually is found as a powder.[\/caption]\r\n\r\nFigure 1.6 \"Describing Matter\"<\/a> is a flowchart of the relationships among the different ways of describing matter.\r\n\r\n[caption id=\"attachment_29\" align=\"aligncenter\" width=\"600\"]\"Matter<\/a> Figure 1.6 \"Describing Matter.\" This flowchart shows how matter can be described.[\/caption]\r\n

                            Chemistry Is Everywhere: In the Morning<\/h1>\r\nMost people have a morning ritual, a process that they go through every morning to get ready for the day. Chemistry appears in many of these activities.\r\n