章节大纲

  • A scientist tests river water for acidity while seated at the water's edge.

    This scientist is collecting and testing samples of water from the river. One of the properties of the water she is testing is acidity . She wants to know how acidic the water is because water that is too acidic can harm the health of water organisms.
    ::这位科学家正在收集和测试河水的样品,她正在测试的水的特性之一是酸性。她想知道水是如何酸化的,因为酸性过强的水会损害水生物的健康。

    Strength of Acids and Bases
    ::酸和碱的强强

    Acids are that produce positively charged hydrogen (H + ) when dissolved in water. Acids taste sour and react with . Bases are ionic compounds that produce negatively charged hydroxide ions (OH - ) when dissolved in water. Bases taste bitter and do not react with metals. Examples of acids are vinegar and battery . The acid in vinegar is weak enough to safely eat on a salad. The acid in a car battery is strong enough to eat through skin. Examples of bases include those in antacid tablets and drain cleaner. Bases in antacid tablets are weak enough to take for an upset stomach. Bases in drain cleaner are strong enough to cause serious burns.
    ::酸是溶于水中时产生正充电氢(H+)的酸; 酸酸酸酸酸酸酸酸酸酸酸酸酸, 与酸反应。 碱性化合物是溶于水时产生负充电氢氧化离子(OH-)的离子化合物; 碱性酸酸, 与金属不发生反应; 酸性酸是醋酸和电池的例子。 醋酸在醋酸中足够弱,足以在沙拉上安全进食。 汽车电池中的酸足以通过皮肤进食; 碱性酸性酸酸足以通过皮肤进食; 碱性酸性药片和排水净化液中的酸。 亚酸性药片中的基体积很弱,足以导致胃不适; 排水净化剂中的酸基足以造成严重烧伤。

    Q: What do you think causes these differences in the strength of acids and bases?
    ::问题:你认为是什么导致酸和碱强度的差异?

    A: The strength of an acid or a depends on how much of it breaks down into ions when it dissolves in water.
    ::A:一种酸或一种酸的强度取决于它溶入水中时分解成离子的程度。

    Concentration of Ions
    ::Ions 浓度

    The strength of an acid depends on how many hydrogen ions it produces when it dissolves in water. A stronger acid produces more hydrogen ions than a weaker acid. For example, sulfuric acid (H 2 SO 4 ), which is found in car batteries, is a strong acid because nearly all of it breaks down into ions when it dissolves in water. On the other hand, acetic acid (CH 3 CO 2 H), which is the acid in vinegar, is a weak acid because less than 1 percent of it breaks down into ions in water.
    ::酸的强度取决于它在水中溶解时产生的氢离子数量。 强酸产生的氢离子比弱酸多。 例如, 在汽车电池中发现的硫酸( H2SO4) 是一种强酸, 因为它几乎都是在水中溶解时分解成离子的。 另一方面, 醋酸( CH3CO2H) 是醋酸中的酸, 是一种弱酸, 因为不到1%的硫酸会分解成水中的离子。

    The strength of a base depends on how many hydroxide ions it produces when it dissolves in water. A stronger base produces more hydroxide ions than a weaker base. For example, sodium hydroxide (NaOH), a base in drain cleaner, is a strong base because all of it breaks down into ions when it dissolves in water. Calcium carbonate (CaCO 3 ), a base in antacids, is a weak base because only a small percentage of it breaks down into ions in water.
    ::基底的强度取决于它溶入水中时产生的氢氧化离子数量。较强的基底产生的氢氧化离子多于较弱的基底。例如,氢氧化钠(NaOH)是排水净化器的基底,是牢固的基底,因为它在溶入水中时会分解成离子。碳酸钙(CaCO3)是炭酸盐的基底,是薄弱的基底,因为只有一小部分分解成水中的离子。

    The pH Scale
    ::pH 缩放

    The strength of acids and bases is measured on a scale called the pH scale, which is shown in the Figure . By definition, pH represents the acidity , or hydrogen ion (H + ) , of a solution. Pure water, which is neutral, has a pH of 7. With a higher the concentration of hydrogen ions, a solution is more acidic and has a lower pH. Acids have a pH less than 7, and the strongest acids have a pH close to zero. Bases have a pH greater than 7, and the strongest bases have a pH close to 14. It’s important to realize that the pH scale is based on powers of ten. For example, a solution with a pH of 8 is 10 times more basic than a solution with a pH of 7, and a solution with a pH of 9 is 100 times more basic than a solution with a pH of 7.
    ::酸和基底的强度在称为pH尺度的尺度上测量,如图所示。按定义,pH代表溶液的酸性或氢离子(H+),纯水中中性,pH值为7。纯水中性,pH值为7,溶液酸性较高,pH值较低,pH值较低。酸的pH值小于7,而最强酸的pH值接近于零。基点的pH值大于7,而最强的基点的pH值接近14。重要的是,必须认识到pH尺度以10的功率为基础。例如,pH值为8的溶液比pH值为7的溶液基本10倍以上,而pH值为9的溶液比pH值为7的溶液基本100倍。

    Q: How much more acidic is a solution with a pH of 4 than a solution with a pH of 7?
    ::问:pH值为4的酸溶液比pH值为7的溶液多多少?

    A: A solution with a pH of 4 is 1000 (10 × 10 × 10, or 10 3 ) times more acidic than a solution with a pH of 7.
    ::A:pH值为4的溶液是1 000(10×10×10,或103),酸度比pH值为7的溶液高一倍(10×10×10,或103)。

    A visual representation of the pH scale ranging from 0 (acidic) to 14 (basic).

    Q: Which solution on the pH scale in the Figure is the weakest acid? Which solution is the strongest base?
    ::问题:图中的pH尺度中哪种溶液是最弱的酸?哪种溶液是最强的基数?

    A: The weakest acid on the scale is milk, which has a pH value between 6.5 and 6.8. The strongest base on the scale is drain cleaner, which has a pH of 14.
    ::甲:规模上最弱的酸是牛奶,其pH值在6.5至6.8之间。 规模上最强的基数是排水净化物,排水净化物的pH值为14。

    Why pH Matters
    ::为什么PH重要

    Acidity is an important factor for living things. For example, many plants grow best in soil that has a pH between 6 and 7. Fish may also need a pH between 6 and 7. Certain air pollutants form acids when dissolved in water droplets in the air. This results in acid fog and acid rain, which may have a pH of 4 or even lower. The pH chart in the Figure and the Figure reveal some of the adverse effects of acid fog and rain. Acid rain not only kills trees. It also lowers the pH of surface waters such as ponds and lakes. As a result, the water may become too acidic for fish and other water organisms to survive.
    ::例如,许多植物在土壤中生长得最佳,其pH值介于6-7之间,鱼类在空气中溶解于水滴中时,可能需要pH值在6-7之间,某些空气污染物形成酸,这导致酸雾和酸雨,酸雾和酸雨的pH值可能为4或更低。图中的pH值图表显示了酸雾和雨的一些不利影响。酸雨不仅杀死树木,还降低了水池和湖泊等地表水的pH值。结果,水变得酸性过大,鱼类和其他水生物无法生存。

    Forest with dead trees showing the effects of acid rain on vegetation.

    Acid fog and acid rain killed the trees in this forest.
    ::酸雾和酸雨杀死了这片森林里的树木

    Even normal (clean) rain is somewhat acidic. That’s because carbon dioxide (CO 2 ) in the air dissolves in raindrops, producing a weak acid called carbonic acid (H 2 CO 3 ), which has a pH of about 5.5. When rainwater soaks into the ground, it can slowly dissolve rocks, particularly those containing calcium carbonate. This is how water forms underground caves.
    ::即使是普通(清洁)雨也有些酸性。 这是因为空气中的二氧化碳(CO2)在雨滴中溶解,产生一种叫做碳酸(H2CO3)的微弱酸(碳酸(H2CO3),其pH值约为5.5。 当雨水渗入地面时,它会慢慢溶解岩石,特别是含碳酸钙的岩石。 这就是水是如何形成地下洞穴的。

    Q: How do you think acid rain might affect buildings and statues made of stone?
    ::问:你觉得酸雨会如何影响石块造的建筑物和雕像?

    A: Acid rain dissolves and damages stone buildings and statues. The Figure shows a statue that has been damaged by acid rain.
    ::A:酸雨溶解并破坏石块建筑和雕像。图中显示一块被酸雨损坏的雕像。

    A damaged stone gargoyle illustrating the effects of acid rain on stone structures.

    Summary
    ::摘要

    • The strength of an acid or base is called acidity. It depends on how much of the substance breaks down into ions when it dissolves in water.
      ::酸或碱的强度被称为酸性,它取决于在水中溶解时该物质的分解成离子的程度。
    • Acidity is measured by pH, which is the concentration of hydrogen ions in a solution.
      ::酸度由pH测量,pH是溶液中氢离子的浓度。
    • Acidity is an important factor for living things because most can survive only within a relatively narrow range of acidity.
      ::酸性是生命的一个重要因素,因为大多数人只能在相对狭窄的酸性范围内生存。

    Review
    ::回顾

    1. What determines how acidic or basic a solution is?
      ::是什么决定了酸性或基本的解决办法是什么?
    2. What is pH? What is the pH of a neutral substance?
      ::PH是什么?中性物质PH是什么?
    3. How much more or less acidic is soapy water than pure water? ( Hint : See the pH chart in the Figure .
      ::肥皂水比纯净水多多少酸? (提示:见图中的pH值图表。
    4. Why is the pH of the environment important for living things?
      ::为什么环境的pH值对生活很重要?