Section outline

  • Sodium reacting with water, creating a large explosion and spray of water.

    Sodium reacts violently with water. That’s what is happening in the picture above. Why does sodium have such explosive reactions? It’s because the reactions occur so quickly.
    ::钠对水反应激烈。 以上情况就是这样。 钠为什么有这种爆炸反应? 这是因为反应发生得太快。

    How Fast Does It Go?
    ::速度有多快? 有多快? 有多快?

    How fast a occurs is called the reaction rate . Several factors affect the rate of a given chemical reaction. They include the:
    ::发生速度有多快被称为反应率。 有几个因素影响特定化学反应率。 它们包括:

    • of reactants .
      ::反应器。
    • of reactants.
      ::反应器。
    • surface area of reactants.
      ::反应器的表面区域。
    • presence of a .
      ::. . . . . . . . . . . .

    Temperature of Reactants
    ::再活性剂温度

    When the temperature of reactants is higher, the rate of the reaction is faster. At higher temperatures, particles of reactants have more , so they move faster. As a result, they are more likely to bump into one another and to collide with greater force. For example, food spoils because of chemical reactions, and these reactions occur faster at higher temperatures (see the bread on the left in the Figure ). This is why we store foods in the refrigerator or freezer (like the bread on the right in the Figure ). The lower temperature slows the rate of spoilage.
    ::当反应物的温度较高时,反应速度会更快。在较高的温度下,反应物的粒子会增加,因此移动速度会更快。因此,它们更有可能相互碰撞,并发生更大的碰撞。例如,由于化学反应造成的食物损耗,这些反应在较高的温度下发生得更快(见图中左边的面包)。这就是为什么我们在冰箱或冷冻器中储存食物的原因(如图中右边的面包)。较低的温度减缓了破坏速度。

    Comparison of moldy bread at room temperature and fresh bread in the refrigerator.

    Left image: Bread after 1 month on a warm countertop. Right image: Bread after 1 month in a cold refrigerator.
    ::左图象: 在一个温暖的柜台, 一个月后的面包。 右图象: 在冷冻冰箱里, 一个月后的面包 。

    Concentration of Reactants
    ::反应剂浓度

    Concentration is the number of particles of a substance in a given volume . When the concentration of reactants is higher, the reaction rate is faster. At higher concentrations, particles of reactants are crowded closer together, so they are more likely to collide and react. Did you ever see a sign like the one in the Figure ? You might see it where someone is using a tank of pure oxygen for a breathing problem. Combustion, or burning, is a chemical reaction in which oxygen is a reactant. A greater concentration of oxygen in the air makes combustion more rapid if a fire starts burning.
    ::当反应器的浓度较高时,反应率会更快。在较高浓度时,反应器的粒子会聚集在一起,因此它们更有可能相撞和反应。你有没有看到像图中那样的信号?你可能看到有人使用纯氧罐处理呼吸问题。燃烧或燃烧是一种化学反应,其中氧是一种反应剂。如果燃烧,空气中的氧浓度越高,燃烧速度就越快。

    A prohibition sign indicating no smoking, emphasizing safety around oxygen use.

    Q: It is dangerous to smoke or use open flames when oxygen is in use. Can you explain why?
    ::问题:使用氧气时吸烟或使用公开火焰是危险的。你能解释为什么吗?

    A: Because of the higher-than-normal concentration of oxygen, the flame of a match, lighter, or cigarette could spread quickly to other materials or even cause an explosion.
    ::甲:由于氧气浓度高于正常浓度,火柴、较轻或香烟的火焰可以迅速扩散到其他材料,甚至引起爆炸。

    Surface Area of Reactants
    ::反应剂表面面积

    When a substance is involved in a chemical reaction, only the matter at the surface of the solid is exposed to other reactants. If a solid has more surface area, more of it is exposed and able to react. Therefore, increasing the surface area of solid reactants increases the reaction rate. Look at the hammer and nails pictured in the Figure . Both are made of iron and will rust when the iron combines with oxygen in the air. However, the nails have a greater surface area, so they will rust faster.
    ::当物质参与化学反应时,只有固体表面的物质与其他反应器接触。如果固体有较多的表面面积,就有更多的接触和反应能力。因此,增加固体反应器的表面面积会提高反应率。看看图中描绘的锤子和钉子。两者都是铁制成的,当铁与空气中的氧合在一起时会生锈。然而,钉子的表面面积更大,因此它们会更快生锈。

    A rusty hammer on the left and rusted nails on the right, illustrating surface area effects.

    Presence of a Catalyst
    ::催化剂的存在

    Some reactions need extra help to occur quickly. They need another substance called a catalyst. A catalyst is a substance that increases the rate of a chemical reaction. A catalyst isn’t a reactant, so it isn’t changed or used up in the reaction. Therefore, it can catalyze many other reactions.
    ::有些反应需要额外的帮助才能迅速发生。 它们需要另一种叫催化剂的物质。 催化剂是一种增加化学反应速度的物质。 催化剂不是反应剂,因此它不会改变或用于反应。 因此,它可以催化许多其他反应。

    Summary
    ::摘要

    • How fast a chemical reaction occurs is called the reaction rate.
      ::化学反应发生的速度,称为反应率。
    • Several factors affect the rate of a chemical reaction, including the temperature, concentration, and surface area of reactants, and the presence of a catalyst.
      ::若干因素影响化学反应的速度,包括反应器的温度、浓度和表面面积,以及催化剂的存在。

    Review
    ::回顾

    1. Define reaction rate.
      ::界定反应率。
    2. List factors that influence the rate of a chemical reaction.
      ::列出影响化学反应率的因素。
    3. Choose one of the factors you listed in your answer to question 2, and explain how it affects reaction rate.
      ::选择您在回答问题2时列出的因素之一, 并解释它是如何影响反应率的 。

    Explore More
    ::探索更多

    Watch the video about reaction rate and then answer the questions below.
    ::观看关于反应率的视频,然后回答下面的问题。

     

     

     

     

     

     

    1. What is collision theory?
      ::什么是碰撞理论?
    2. How does collision theory relate to factors that affect reaction rate?
      ::碰撞理论与影响反应率的因素有何关联?

    Resources
    ::资源