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  • A man with a sour expression bites into a lemon, highlighting its sour taste.

    Look at the man in the photo above. You can tell by the expression on his face that lemon juice tastes sour. Lemon juice is an acid, and all acids taste sour. They share certain other properties as well. You will learn more about acids and their properties in this article. 
    ::看看上面照片中的人。你可以从他脸上的表情看出柠檬汁是酸的。柠檬汁是酸的,所有酸汁都是酸的。它们也有其他的特性。你会在文章中更多地了解酸和酸的特性。

    What Are Acids?
    ::什么是酸?

    Acids are compounds that produce positive hydrogen (H + ) when dissolved in water. Often they are , which are compounds that contain positive metal ions and negative ions held together by . (Ions are atoms that have become charged particles by gaining or losing electrons.) An example of an acid is hydrogen chloride (HCl). When it dissolves in water, it separates into positive hydrogen ions and negative chloride ions (Cl - ). This is represented by the chemical equation :
    ::酸是水溶解后产生正氢(H+)的化合物,往往是含有正金属离子和由.(原子通过获取或丧失电子而成为有电粒子的电原子)所联结的负离子(H+)的化合物。酸的例子之一是氯化氢(HCl)。当酸溶解于水中时,它会分离成正氢离子和负氯化离子(Cl-)。这表现为化学方程式:

    HCl → H 2 O H + + Cl -

    Properties of Acids
    ::酸的属性

    You already know that a sour taste is one property of acids. ( Warning : Never taste an unknown substance to see whether it is an acid!) Acids have certain other properties as well. For example, acids can conduct electricity when dissolved in water because they consist of charged particles in solution. ( Electric current is a flow of charged particles.) Acids can also react with , and when they do they produce hydrogen . An example of this type of reaction is hydrochloric acid reacting with the metal zinc (Zn). The reaction is pictured in the Figure . It can be represented by the chemical equation:
    ::您已经知道酸酸的味道是酸的一种特性。 (警告:不要尝到未知物质,看它是否是酸!) 酸也具有某些其他特性。例如,酸在溶水中溶解时可以使用电,因为它们是由溶液中的有电颗粒组成。 (电流是有电颗粒的流。) 酸也可以与产生氢时发生反应。 这种反应的一个例子是盐酸与金属锌(Zn)发生反应。 图中描绘了这种反应。 它可以用化学方程式表示 :

    Zn + 2HCl → H 2 + ZnCl 2
    A test tube showing bubbles, indicating hydrogen gas produced from zinc reacting with hydrochloric acid.
    Hydrochloric acid reacting with the metal zinc.

    Q: What sign indicates that a gas is being produced in this reaction?
    ::问题:什么迹象显示在这一反应中正在产生气体?

    A: The bubbles are hydrogen gas rising through the acid.
    ::A:泡沫是氢气在酸中上升。

    Q: Besides hydrogen gas, what else is produced in this reaction?
    ::问:除了氢气之外,这种反应还能产生什么?

    A: This reaction also produces zinc chloride ZnCl 2 , which is a neutral ionic compound called a salt .
    ::A:这种反应还产生氯化锌ZnCl2,这是一种中性离子化合物,称为盐。

    Detecting Acids
    ::检测酸

    Certain compounds, called indicators, change color when acids come into contact with them, so indicators can be used to detect acids. An example of an indicator is the called litmus. It is placed on small strips of paper that may be red or blue. If you place a few drops of acid on a strip of blue litmus paper, the paper will turn red. You can see this in the Figure  . Litmus isn’t the only indicator for detecting acids. Red cabbage juice also works well, as you can see in this entertaining video .
    ::某些化合物,称为指标,在酸接触时会改变颜色,因此,指标可以用来检测酸。一个指标的例子就是所谓的亮度。它放在红色或蓝色的小纸条上。如果你在蓝色的亮度纸条上放上几滴酸,纸就会变成红色。在图中可以看到这一点。Litmus并不是检测酸的唯一指标。红卷心菜果汁也很好用,正如你在这个有趣的视频中看到的那样。

     

     

    Blue litmus paper changing to red when dipped in an acidic solution.
    Drawing of blue litmus paper turning red in acid.

    Strength of Acids
    ::酸的强度

    The strength of acids is measured on a scale called the scale. The pH value of a solution represents its of hydrogen ions. A pH value of 7 indicates a neutral solution, and a pH value less than 7 indicates an acidic solution. The lower the pH value is, the greater is the concentration of hydrogen ions and the stronger the acid. The strongest acids, such as battery acid, have pH values close to zero.
    ::酸的强度是在一个称为比例尺的尺度上测量的。溶液的pH值代表氢离子的pH值。一个pH值为7表示中性溶液,而一个pH值小于7表示酸溶液。pH值越低,氢离子的浓度就越高,酸就越强。最强的酸,如电池酸,其pH值接近于零。

    Uses of Acids
    ::酸的使用

    Acids have many important uses, especially in industry. For example, sulfuric acid is used to manufacture a variety of different products, including paper, paint, and detergent. Some other uses of acids are be seen in the Figure  .
    ::例如,硫酸被用于制造各种不同的产品,包括纸张、油漆和洗涤剂。

    Various acids and their uses: fertilizers, hydrochloric acid, and a car battery.
    Nitric acid and Phosphoric acid: Both nitric acid and phosphoric acid are used to make fertilizer. Hydrochloric acid: Hydrochloric acid is used to clean swimming pools, bricks, and concrete. Sulfuric acid: Sulfuric Acid is an important component of car batteries.

    Summary
    ::摘要

    • Acids are ionic compounds that produce positive hydrogen ions (H + ) when dissolved in water.
      ::酸是溶于水时产生正氢离子(H+)的离子离子(H+)的离子化合物。
    • Acids taste sour, conduct electricity when dissolved in water, and react with metals to produce hydrogen gas.
      ::酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸酸
    • Certain indicator compounds, such as litmus, can be used to detect acids. Acids turn blue litmus paper red.
      ::某些指示化合物,如闪石,可用于检测酸性,酸会变成蓝色亮石纸红色。
    • The strength of acids is measured on the pH scale. A pH value less than 7 indicates an acid, and the lower the number is, the stronger the acid.
      ::酸的强度在 pH 尺度上测量。 pH 值小于 7 表示酸, 数值越低, 酸越强。
    • Acids have many important uses, especially in industry.
      ::酸有很多重要的用途,特别是在工业中。

    Review
    ::回顾

    1. What is an acid?
      ::酸是什么? 酸吗?
    2. List properties of acids.
      ::列出酸性。
    3. How can you tell whether a compound is an acid?
      ::你怎么能分辨化合物是不是酸?
    4. Milk is a very weak acid. What might its pH value be?
      ::牛奶是一种非常微弱的酸。它的pH值是什么?
    5. Based on your knowledge of the properties of acids, which one of the following substances do you think is an acid?
      1. vinegar
        ::醋醋
      2. salt
        ::盐盐盐
      3. sugar
        ::糖糖糖糖
      4. baking soda
        ::苏打汽水

      ::根据你对酸的特性的了解, 你认为以下物质中哪一种是酸? 醋盐糖烘制苏打水。

    Explore More
    ::探索更多

    Watch these videos about hydrochloric acid, and then answer the questions below.
    ::观看这些关于盐酸的视频, 然后回答下面的问题。

     

     

    1. What is hydrochloric acid?
      ::什么是盐酸?
    2. Everyone carries around a sample of hydrochloric acid. Where is the hydrochloric acid, and what is its function?
      ::每个人都携带着盐酸样本。盐酸在哪里?它的作用是什么?
    3. Describe what happens when a cheeseburger and then a goose skull are placed in hydrochloric acid.
      ::描述当一个芝士汉堡和一个鹅头盖骨被放入盐酸时会发生什么。
    4. When zinc metal is added to hydrochloric acid, how can you tell that hydrogen gas is produced?
      ::当锌金属添加到盐酸中时,你如何知道氢气是生产的?

    Resources
    ::资源