Section outline

  • General

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  • 能源和生化反应

    What will you learn
    ::你会学到什么

    • How energy is involved in a chemical reaction
      ::如何在化学反应中涉及能源
    • Endothermic and exothermic reactions
      ::局部热和体外热反应

    A team of ants working together to break down a dead tree.

    What is energy? Where does your energy come from? Can energy be recycled?
    ::能量是什么 你的能量来自何方?能源可以回收吗?

    This team of ants is breaking down a dead tree. A classic example of teamwork. And all that work takes energy. In fact, each chemical reaction - the chemical reactions that allow the in those ants to do the work - needs energy to get started. And all that energy comes from the food the ants eat. Whatever eats the ants gets their energy from the ants. Energy passes through an in one direction only.
    ::这群蚂蚁正在摧毁一棵枯树。一个典型的团队合作范例。所有工作都需要能量。事实上,每一种化学反应 — — 允许蚂蚁做工的化学反应 — — 都需要能量才能启动。所有能量都来自蚂蚁吃的食物。无论蚂蚁吃什么,它们都能从蚂蚁身上得到能量。能源仅向一个方向扩散。

    Chemical Reactions and Energy
    ::化学反应和能源

    Chemical reactions always involve energy. Energy is a property of matter that is defined as the ability to do work. When methane burns, for example, it releases energy in the form of heat and light. Other chemical reactions absorb energy rather than release it.
    ::化学反应总是涉及能源。能源是一种物质特性,被定义为工作能力。例如,当甲烷燃烧时,它以热和光的形式释放能量,其他化学反应吸收能量而不是释放能量。

    Exothermic Reactions
    ::异热反应

    A chemical reaction that releases energy (as heat) is called an exothermic reaction . This type of reaction can be represented by a general chemical equation :
    ::释放能量(作为热)的化学反应称为异温反应。

    Reactants → Products + Heat
    ::反应剂 + 产品+热

    In addition to methane burning, another example of an exothermic reaction is chlorine combining with sodium to form table salt. This reaction also releases energy.
    ::除了甲烷燃烧之外,另一种异温反应的例子是氯与钠结合形成食盐,这种反应还释放出能量。

    DID YOU KNOW?
    is a series of exothermic reactions that occur in order to release energy from food molecules.
     

    Endothermic Reaction
    ::内热反应

    A chemical reaction that absorbs energy is called an endothermic reaction . This type of reaction can also be represented by a general chemical equation:
    ::吸收能量的化学反应称为内温反应。这种反应也可以用一般化学方程式表示:

    Reactants + Heat → Products
    ::活性剂 +热 + 热 + 产品

    Did you ever use a chemical cold pack? The pack cools down because of an endothermic reaction. When a tube inside the pack is broken, it releases a chemical that reacts with inside the pack. This reaction absorbs heat energy and quickly cools down the pack.
    ::你曾经使用过化学冷却包吗? 包会因为内热反应而冷却下来。 当包内管破裂时, 它会释放出一种化学物质, 与包内发生反应。 这种反应吸收了热能, 并很快冷却了包。

    Activation Energy
    ::能源

    All chemical reactions need energy to get started. Even reactions that release energy need a boost of energy in order to begin. The energy needed to start a chemical reaction is called activation energy . Activation energy is like the push a child needs to start going down a playground slide. The push gives the child enough energy to start moving, but once she starts, she keeps moving without being pushed again. Activation energy is illustrated in the Figure .
    ::所有化学反应都需要能量才能启动。即使释放能量的反应也需要能量来启动。启动化学反应所需的能量被称为激活能量。激活能量就像一个孩子需要从游乐场滑动的推力。推力让孩子有足够的能量开始运动,但一旦她开始,她就会不停地移动,不再被推动。振动能量在图中显示。

    Graph showing energy transition from reactants to products, highlighting activation energy in chemical reactions.
    Activation energy provides the “push” needed to start a chemical reaction. Is the chemical reaction in this figure an exothermic or endothermic reaction?

    Why do all chemical reactions need energy to get started? In order for reactions to begin, reactant molecules must bump into each other, so they must be moving, and movement requires energy. When reactant molecules bump together, they may repel each other because of intermolecular forces pushing them apart. Overcoming these forces so the molecules can come together and react also takes energy.
    ::为什么所有化学反应都需要能量才能启动?为了开始反应,反应分子必须相互碰撞,因此它们必须移动,而移动需要能量。 当反应分子聚集在一起时,它们可能会因为分子的间歇性力量将它们分开而互相击退。 克服这些力量,让分子聚集起来,反应也需要能量。

     

     

    Summary
    ::摘要

    • Chemical reactions always involve energy.
      ::化学反应总是涉及能量。
    • A chemical reaction that releases energy is an exothermic reaction, and a chemical reaction that absorbs energy is an endothermic reaction.
      ::释放能量的化学反应是一种异温反应,吸收能量的化学反应是一种异温反应。
    • The energy needed to start a chemical reaction is the activation energy.
      ::启动化学反应所需的能量是激活能量。

    Review
    ::回顾

    1. What is an exothermic reaction?
      ::什么是异热反应?
    2. What is the general chemical equation for an endothermic reaction?
      ::通热反应的一般化学方程是什么?
    3. What is the activation energy?
      ::激活能量是什么?
    4. Why do all chemical reactions require activation energy?
      ::为什么所有化学反应都需要激活能量?