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  • 化学物质 - 先进

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    Take some Cs, Hs, Ns, Os, Ps, and Ss, combine them in many different combinations, and what do you get?
    ::采取一些C、H、N、O、P和S, 以多种不同的组合组合组合组合,你得到什么?

    In just the right combinations, you get life. Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. Some of the most basic of elements , but some of the most important. Together they can form countless combinations of . And in just the right combinations, anything can happen.
    ::碳、氢、氮、氧、磷和硫。一些最基本的元素,但其中最重要的部分。它们可以形成无数的组合。在正确的组合中,任何事情都会发生。

    Chemical Substances
    ::化学物质

    Living things are made of matter. In fact, matter is the “stuff” of which all things are made. Anything that occupies space and has mass is known as matter. Matter, in turn, consists of chemical substances. A chemical substance is a material that has a definite chemical composition. It is also homogeneous, so the same chemical composition is found uniformly throughout the substance. A chemical substance may be an element or a chemical compound.
    ::事实上,物质是所有事物所制造的“物质”。 占据空间和质量的任何物质都被称为物质。 物质又由化学物质组成。 化学物质是具有确定化学成分的材料。 化学物质也是同质的, 因而该物质的所有化学成分都是相同的。 化学物质可以是元素,也可以是化学化合物。

    Elements
    ::要件要件要件

    An element is a pure substance that cannot be broken down into different types of substances. There are almost 120 known elements ( Figure  ), each with its own personality. The chemical and physical properties of one element differ from any other. Elements are arranged according to their properties in the Periodic Table .
    ::元素是一种纯物质,不能细分为不同类型的物质,有近120种已知元素(图),每个元素都有自己的个性,一个元素的化学和物理特性不同于任何其他元素,元素按其特性在周期表中排列。

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    The Periodic Table.

    Examples of elements include carbon, oxygen, hydrogen, gold, silver and iron. Each element is made up of just one type of atom. An atom is the smallest particle of an element that still characterizes the element. As shown in Figure   , at the center of an atom is a . The nucleus contains positively charged particles called protons and electrically neutral particles called neutrons. Surrounding the nucleus is a much larger electron cloud consisting of negatively charged electrons. Electrons are arranged into distinct energy levels, at various distances from the nucleus. An atom is electrically neutral if it has the same number of protons as electrons. Each element has atoms with a characteristic number of protons, which defines the atomic number of the element. For example, all carbon atoms have six protons, and all oxygen atoms have eight protons. A combination of the number of protons and neutrons in the nucleus gives the approximate atomic mass of the atom, measured in an amu, or atomic mass unit. For example, hydrogen has an atomic number of 1 and an atomic mass of 1.00794 amu; carbon has an atomic number of 6 and an atomic mass of 12.0107 amu; oxygen has an atomic number of 8 and an atomic mass of 15.9994 amu. 
    ::元素示例包括碳、 氧、 氢、 金、 银和铁等元素。 每个元素由一种原子组成。 每个元素仅由一种原子组成。 原子是一个元素的最小粒子, 其特性仍然是元素。 如图所示, 原子的中心是一个。 如图所示, 原子的中心是一个。 核中含有积极充电的粒子, 叫做质子和中中性粒子。 包围核是一个大得多的电子云, 由负电荷构成。 电离核的不同距离, 将电子排列成不同的能量水平。 如果原子的质子数量与电子相同, 原子是中和的。 每个元素的原子都有质子特性的最小粒子。 如图所示, 原子的中心是一个。 如, 所有碳原子有6个质子, 所有氧原子有8个质子。 核中质子和中中中中中中子的质子数量提供了原子的大约原子原子质量。 例如, 氢有1个原子数, 和1, 001原子的原子数量为1. 94; 原子原子的原子数。

    The majority of known elements are classified as metals. Metals are elements that are lustrous, or shiny. They are also good conductors of electricity and heat. Examples of metals include iron, gold, and copper. Fewer than 20 elements are classified as nonmetals. Nonmetals lack the properties of metals. Examples of nonmetals include oxygen, hydrogen, and sulfur. Certain other elements have properties of both metals and nonmetals. They are known as metalloids. Examples of metalloids include silicon and boron.
    ::已知元素大多被归类为金属,金属是光亮或闪亮的元素,也是电力和热能的良好导体,金属的例子包括铁、金和铜,不到20个元素被归类为非金属,非金属缺乏金属特性,非金属的例子包括氧、氢和硫,某些其他元素具有金属和非金属特性,它们被称为类动物,类动物的例子包括硅和。

    Chemical Compounds
    ::化学化合物

    A chemical compound is a new substance that forms when atoms of two or more elements react with one another. A chemical reaction is a process that changes some chemical substances into other chemical substances. A compound that results from a chemical reaction always has a unique and fixed chemical composition. The substances in the compound can be separated from one another only by another chemical reaction. This is covered further in Concept Biochemistry (Advanced) . Atoms bond with each other through the interactions of their electrons, specifically their outermost or valence electrons.
    ::当两个或两个以上元素的原子相互反应时,一种化学化合物是一种新物质。一种化学反应是一种将某些化学物质改变为其他化学物质的过程。一种化学反应产生的化合物总是具有独特的固定化学成分。该化合物中的物质只能通过另一种化学反应相互分离。这在“生物化学概念”(高级)中作了进一步阐述。原子通过电子的相互作用,特别是其最外层或价值电子的相互作用而相互连接。

    The atoms of a compound are held together by chemical bonds . Chemical bonds form when atoms share electrons. There are different types of chemical bonds, and they vary in how strongly they hold together the atoms of a compound. Two of the strongest types of bonds are covalent and ionic bonds. Covalent bonds form between atoms that have little if any difference in electronegativity, and result when atoms share electrons. Electronegativity is the power of an atom to attract electrons toward itself. Ionic bonds , in contrast, form between atoms that are significantly different in electronegativity. An ion is an atom that has gained or lost at least one electron. Ionic bonds form between ions of opposite charges.
    ::一种化合物的原子由化学键组成。当原子分享电子时,化学键会形成化学债券。有不同种类的化学债券,它们将一个化合物的原子维持在一起的强度不同。两种最强的债券类型是共价债券和离子债券。在电子密度方面几乎没有任何差别的原子之间形成共价债券,在原子分享电子时形成共价债券。电抗力是原子吸引电子到自己身上的力量。相反,在电子密度方面差异很大的原子之间形成离子债券。离子是至少一种电子电离的原子,增减至少一种电子。相反电离的离子之间形成共价债券形式。

    An example of a chemical compound is . A water molecule forms when oxygen (O) and hydrogen (H) atoms react and are held together by covalent bonds. Like other compounds, water always has the same chemical composition: a 2:1 ratio of hydrogen atoms to oxygen atoms. This is expressed in the chemical formula H 2 O. A model of a water molecule is shown in Figure  .
    ::化学化合物的一个例子是:当氧(O)和氢(H)原子发生反应时,水分子形式会形成一种水分子,并用共价联结在一起。与其他化合物一样,水总是具有相同的化学成分:氢原子与氧原子的比例为2:1。这表现在化学公式H2O中。一个水分子模型在图中显示。

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    Model of a water molecule, showing the arrangement of hydrogen and oxygen atoms. The protons (8 in oxygen, 1 in hydrogen) and neutrons (8 in oxygen) are depicted in the nucleus.

    Compounds that contain mainly the elements carbon and hydrogen are called organic compounds . This is because they are found mainly in living organisms . Most organic compounds are held together by covalent bonds. An example of an organic compound is glucose (C 6 H 12 O 6 ), which is shown in Figure  . Glucose is a simple sugar that living use for energy. All other compounds are called inorganic compounds. Water is an example of an inorganic compound.
    ::主要含有元素碳和氢的化合物称为有机化合物,因为主要在活体中发现,大多数有机化合物由共价结合物粘合在一起,有机化合物的一个例子是葡萄糖(C6H12O6),如图6所示。甘蔗糖是一种简单的糖,可以用作能源,所有其他化合物都被称为无机化合物。水是无机化合物的一个例子。水是无机化合物的一个例子。

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    Glucose Molecule. This model represents a molecule of glucose, an organic compound composed of carbon, hydrogen, and oxygen. The chemical formula for glucose is C6H12O6. This means that each molecule of glucose contains six carbon atoms, twelve hydrogen atoms, and six oxygen atoms. NOTE: Each unlabeled point where lines intersect represents another carbon atom. Some of these carbons and the oxygen atom are bonded to another hydrogen atom, not shown here.

    Mixtures vs. Compounds
    ::混合体与化合物

    Like a chemical compound, a mixture consists of more than one chemical substance. Unlike a compound, a mixture does not have a fixed chemical composition. The substances in a mixture can be combined in any proportions. A mixture also does not involve a chemical reaction. Therefore, the substances in a mixture are not changed into unique new substances, and they can be separated from each other without a chemical reaction.
    ::与一种化学化合物一样,一种混合物由多种化学物质组成,与一种化合物不同,一种混合物没有固定的化学成分,一种混合物中的物质可以任何比例地混合。一种混合物中的物质也不涉及化学反应。因此,一种混合物中的物质不会改变为独特的新物质,它们可以相互分离而无需化学反应。

    The following examples illustrate these differences between mixtures and compounds. Both examples involve the same two elements: the metal iron (Fe) and the nonmetal sulfur (S).
    ::以下例子说明了混合物和化合物之间的这些差异,两个例子都涉及相同的两个要素:金属铁(Fe)和非金属硫(S)。

    • When iron filings and sulfur powder are mixed together in any ratio, they form a mixture. No chemical reaction occurs, and both elements retain their individual properties. A magnet can be used to mechanically separate the two elements by attracting the iron filings out of the mixture and leaving the sulfur behind.
      ::当铁制成和硫粉混合在一起时,铁制成混合物,不发生化学反应,两种元素都有各自的特性。 磁铁可以用来机械地分离这两种元素,将铁制成材料从混合物中吸引出来,将硫制留在后面。
    • When iron and sulfur are mixed together in a certain ratio and heated, a chemical reaction occurs. This results in the formation of a unique new compound, called iron sulfide (FeS). A magnet cannot be used to mechanically separate the iron from the iron sulfide because metallic iron does not exist in the compound. Instead, another chemical reaction is required to separate the iron and sulfur.
      ::当铁和硫在一定比例下混合并加热时,就会发生化学反应,从而形成一种独特的新化合物,称为硫化铁(FeS),磁铁不能用来机械地将铁与硫化铁分离,因为化合物中不存在金属铁。相反,需要另一种化学反应来分离铁和硫化物。

    Summary
    ::摘要

    • Matter consists of elements and compounds.
      ::物质由元素和化合物组成。
    • A compound forms when elements combine in fixed proportions and undergo a chemical reaction.
      ::当元素以固定比例结合并进行化学反应时,构成化合物。
    • A mixture forms when substances combine in any proportions without a chemical reaction.
      ::当物质在任何比例上结合而没有化学反应时,混合物即构成混合物。

    Review
    ::回顾

    1. Define element, and give an example of an element.
      ::定义元素, 并给出元素示例 。
    2. State how a compound differs from an element, and give an example of a compound.
      ::说明化合物与元素有何不同,并举例说明化合物。
    3. Compare and contrast mixtures and compounds.
      ::比较和对比混合物和化合物。
    4. Describe the difference between an ionic bond and a covalent bond.
      ::描述离子债券和共价债券之间的区别。