{"id":81,"date":"2018-03-19T15:28:49","date_gmt":"2018-03-19T15:28:49","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-orgbiochemistry\/chapter\/the-classification-of-matter\/"},"modified":"2018-07-29T19:30:33","modified_gmt":"2018-07-29T19:30:33","slug":"the-classification-of-matter","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-monroecc-orgbiochemistry\/chapter\/the-classification-of-matter\/","title":{"raw":"1.2 The Classification of Matter","rendered":"1.2 The Classification of Matter"},"content":{"raw":"
\r\n
\r\n

Learning Objectives<\/h3>\r\n
\r\n
\r\n
\r\n
    \r\n \t
  1. Use physical and chemical properties, including phase, to describe matter.<\/li>\r\n \t
  2. Identify a sample of matter as an element, a compound, or a mixture.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n \r\n
    \r\n

    Physical and Chemical Properties<\/h2>\r\n<\/div>\r\n
    \r\n
    \r\n
    \r\n

    Part of understanding matter is being able to describe its properties, which fall into two general categories. Physical properties<\/strong>\u00a0are characteristics that describe matter. Physical properties include size, shape, color, mass, state of matter, solubility, boiling point, and melting point. \u00a0 Chemical properties<\/strong>\u00a0<\/span>are characteristics that describe how matter reacts, changing its chemical structure or composition. Chemical properties include flammability, ability to support combustion, corrosive nature, susceptibility to corrosion, and even lack<\/em> of reactivity.<\/p>\r\n\r\n<\/div>\r\n

    \r\n

    Elements and Compounds<\/h2>\r\n

    Any sample of matter that has the same physical and chemical properties throughout the sample is called a substance<\/span><\/strong>. There are two types of substances. A substance that cannot be broken down into chemically simpler components is an element<\/span><\/strong>. Aluminum, which is used in soda cans, is an element. A substance that can be broken down into chemically simpler components (because it has more than one element) is a compound<\/b><\/span>\u00a0(Figure 1.2<\/a>). Water is a compound composed of the elements hydrogen and oxygen. There are 118 elements currently known. In contrast, scientists have identified tens of millions of different compounds to date.<\/p>\r\n\r\n

    \r\n
    \r\n

    Note<\/h3>\r\n

    Sometimes the word pure<\/em> is added to substance, but this is not absolutely necessary. By definition, any single substance is pure.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n

    The smallest part of an element that maintains the identity of that element is called an atom<\/span><\/strong>. Atoms are extremely tiny; to make a line 1 inch long, you would need 217 million iron atoms. The smallest part of a compound that maintains the identity of that compound is called a molecule <\/span><\/strong>(for covalent compounds) or formula unit <\/strong>(for ionic compounds)<\/span>. A molecule is composed of atoms that are bonded together and behave as one particle. A formula unit is composed of a the smallest ratio of positive and negative ions that results in a neutral compound.\u00a0 Scientists usually work with huge numbers of atoms, molecules, and formula units at a time. This large-scale version of chemistry that is observable with our senses is called the\u00a0 macroscopic<\/strong>\u00a0view. However, scientists can also describe chemical events on the level of individual atoms, molecules, or ions, the microscopic<\/span><\/strong> or particle-level <\/strong>viewpoint. We will see examples of both macroscopic and microscopic viewpoints throughout this book (Figure 1.3<\/a>).<\/p>\r\n\r\n

    \r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"1230\"]\"image\" Figure 1.3 How Many Particles Are Needed for a Period in a Sentence?[\/caption]\r\n

    Although we do not notice it from a macroscopic perspective, matter is composed of microscopic particles so tiny that billions of them are needed to make a speck we can see with the naked eye. The \u00d725 and \u00d7400,000,000 indicate the number of times the image is magnified.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n

    \r\n

    Mixtures<\/h2>\r\n

    A material composed of two or more substances is a mixture<\/span><\/strong>. In a mixture, the individual substances maintain their chemical identities. Many mixtures are obvious combinations of two or more substances, such as a mixture of sand and water. Such mixtures are called\u00a0heterogeneous mixtures.\u00a0<\/strong>In some mixtures, the components mingle at the particle level, and the mixture may seem like a single substance. These mixtures have a consistent proportion of components throughout and are called homogeneous mixtures<\/strong> or solutions<\/strong>. Sugar dissolved in water is an example of a solution. All metal alloys, such as steel and brass, are examples of\u00a0 solid solutions. Air, a mixture of mainly nitrogen and oxygen, is a gaseous solution.\u00a0 A solution can be separated into its components by physical means, but breaking apart a compound requires a chemical reaction.<\/p>\r\n\r\n

    \r\n

    Example<\/h3>\r\n

    How would a chemist categorize each example of matter?<\/p>\r\n\r\n

      \r\n \t
    1. saltwater<\/li>\r\n \t
    2. soil<\/li>\r\n \t
    3. water<\/li>\r\n \t
    4. oxygen<\/li>\r\n<\/ol>\r\n

      [reveal-answer q=\"309649\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"309649\"]<\/p>\r\n\r\n

        \r\n \t
      1. Saltwater acts as if it were a single substance even though it contains two substances\u2014salt and water. Saltwater is a homogeneous mixture, or a solution.<\/li>\r\n \t
      2. Soil is composed of small pieces of a variety of materials, so it is a heterogeneous mixture.<\/li>\r\n \t
      3. Water is a substance; more specifically, because water is composed of hydrogen and oxygen, it is a compound.<\/li>\r\n \t
      4. Oxygen, a substance, is an element.[\/hidden-answer]<\/li>\r\n<\/ol>\r\n<\/div>\r\n
        \r\n
        \r\n

        Skill-Building Exercise<\/h3>\r\n
        \r\n\r\nHow would a chemist categorize each example of matter?\r\n
          \r\n \t
        1. coffee<\/li>\r\n \t
        2. hydrogen<\/li>\r\n \t
        3. an egg<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n

          Phases<\/span><\/h2>\r\nAnother way to classify matter is to describe it as a solid, a liquid, or a gas, which was done in the examples of solutions. These three descriptions, each implying that the matter has certain physical properties, represent the three phases<\/strong>\u00a0<\/span><\/span>of matter. A solid has a definite shape and a definite volume. Liquids ordinarily have a definite volume but not a definite shape; they take the shape of their containers. Gases have neither a definite shape nor a definite volume, and they expand to fill their containers. We encounter matter in each phase every day; in fact, we regularly encounter water in all three phases: ice (solid), water (liquid), and steam (gas).\u00a0 Kinetic molecular theory <\/strong>explains the properties of the phases based on the arrangement and movement of chemical particles.\u00a0 In a solid, the particles are generally close together and orderly, and their only movement is to vibrate in place.\u00a0 In a liquid, the particles are close together but disorderly, randomly moving around.\u00a0 In a gas, the particles are very far apart and move quite rapidly in straight lines, occasionally bouncing off of each other or off of the walls of the container.\r\n<\/span>\r\n\r\n<\/div>\r\n<\/div>\r\n
          \r\n

          We know from our experience with water that substances can change from one phase to another if the conditions are right. Typically, varying the temperature of a substance (and, less commonly, the pressure exerted on it) can cause a phase\u00a0<\/strong>change<\/b>, a physical process in which a substance goes from one phase to another (Figure 1.4<\/a>). As explained by kinetic mollecular theory, when chemical particles absorb energy, they move faster, and their motion may cause the sample to transition from a less mobile phase (solid or liquid) to a more mobile phase (liquid or gas).\u00a0 Phase changes have particular names depending on what phases are involved, as summarized in Table 1.1. <\/a><\/p>\r\n\r\n

          \r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
          Table 1.1<\/span> Phase Changes<\/th>\r\n<\/tr>\r\n
          Change<\/th>\r\nName<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
          solid to liquid<\/td>\r\nmelting, fusion<\/td>\r\n<\/tr>\r\n
          solid to gas<\/td>\r\nsublimation<\/td>\r\n<\/tr>\r\n
          liquid to gas<\/td>\r\nvaporization (boiling, evaporation)<\/td>\r\n<\/tr>\r\n
          liquid to solid<\/td>\r\nsolidification, freezing<\/td>\r\n<\/tr>\r\n
          gas to liquid<\/td>\r\ncondensation<\/td>\r\n<\/tr>\r\n
          gas to solid<\/td>\r\ndeposition<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n

          Figure 1.5<\/a> illustrates the relationships between the different ways matter can be classified.<\/p>\r\n\r\n

          \r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"1324\"]\"image\" Figure 1.5 The Classification of Matter[\/caption]\r\n\r\n \r\n\r\n<\/div>\r\n
          \r\n
          \r\n
          \r\n

          Concept Review Exercises<\/h3>\r\n
            \r\n \t
          1. \r\n
            \r\n

            Explain the differences between the physical properties of matter and the chemical properties of matter.<\/p>\r\n\r\n<\/div><\/li>\r\n \t

          2. \r\n
            \r\n

            What is the difference between a heterogeneous mixture and a homogeneous mixture? Give an example of each.<\/p>\r\n\r\n<\/div><\/li>\r\n<\/ol>\r\n

            \r\n

            Give at least two examples of a phase change and state the phases involved in each.<\/p>\r\n

            [reveal-answer q=\"68328\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"68328\"]<\/p>\r\n\r\n

              \r\n \t
            1. Physical properties describe the existence of matter, and chemical properties describe how substances change into other substances.<\/li>\r\n \t
            2. A heterogeneous mixture is obviously a mixture, such as dirt; a homogeneous mixture behaves like a single substance, such as saltwater. Solid to liquid (melting) and liquid to gas (boiling) (answers will vary)\u00a0[\/hidden-answer]<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
              <\/div>\r\n<\/div>\r\n
              \r\n
              \r\n

              Key Takeaways<\/h3>\r\n<\/div>\r\n
              \r\n