Endothermic and Exothermic Processes · 吸热与放热过程
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| exothermic/eɡzəˈðɜːmɪk/ | 放热 | fàng rè |
| endothermic/ˌendəʊˈθɜːmɪk/ | 吸热 | xī rè |
Heat in, heat out
- A hand warmer gets hot; an instant cold pack turns icy.
- Both are chemistry moving heat around.
- Some changes pour heat out; others soak it up.
- The direction of that heat flow has a name.
热进,热出
- 暖手宝会发热;速冷袋变得冰凉。
- 两者都是化学在搬运热。
- 有些变化倾泻出热;有些则吸收热。
- 那份热流的方向有个名字。
Releasing heat
- An exothermic 放热 process releases heat to the surroundings.
- It feels hot, and its $\Delta H$ is negative.
- Burning and freezing are exothermic.
放出热
- 放热过程向周围环境放出热。
- 它摸起来热,它的 $\Delta H$ 为负。
- 燃烧和凝固是放热的。
An exothermic reaction has a $\Delta H$ that is... · 放热反应的$\Delta H$是...
Releasing heat makes $\Delta H$ negative. · 释放热量使$\Delta H$变为负值。
An exothermic process releases heat to the ____. · 放热过程向____释放热量。
Heat flows from the system out to the surroundings. · 热量从系统流向环境。
Absorbing heat
- An endothermic 吸热 process absorbs heat from the surroundings.
- It feels cold, and its $\Delta H$ is positive.
- Melting and evaporating are endothermic.
吸收热
- 吸热过程从周围环境吸收热。
- 它摸起来凉,它的 $\Delta H$ 为正。
- 熔化和蒸发是吸热的。
Endothermic or exothermic? · 吸热还是放热？
Sort each process by whether it releases or absorbs heat. · 根据释放或吸收热量对每个过程进行分类。
A reaction that makes its container feel cold is... · 使容器感觉寒冷的反应是...
Absorbing heat from your hand feels cold -- endothermic. · 从手中吸收热量感觉寒冷——这是吸热过程。
Select all · 所有 exothermic processes. · 选择所有放热过程。
Burning and freezing release heat; melting absorbs it. · 燃烧和结冰释放热量；融化吸收热量。
Breaking and making bonds
- Breaking bonds absorbs energy; making bonds releases it.
- If more is released than absorbed, the reaction is exothermic overall.
- The balance of the two sets the sign of $\Delta H$.
断键与成键
- 断键吸收能量;成键放出能量。
- 若放出的多于吸收的,反应整体上放热。
- 两者的平衡决定 $\Delta H$ 的符号。
Breaking a chemical bond... · 断裂化学键...
Breaking bonds always requires (absorbs) energy. · 断键总是需要（吸收）能量。
Forming a chemical bond releases energy. · 形成化学键释放能量。
Bond formation is exothermic -- the opposite of breaking. · 成键是放热的——与断键相反。
Is burning methane exothermic or endothermic?
- It releases a lot of heat, since the flame is hot.
- So it is exothermic, with a negative $\Delta H$.
甲烷燃烧是放热还是吸热?
- 它放出大量的热,因为火焰是热的。
- 所以它是放热的,$\Delta H$ 为负。
Mind the sign: exothermic $\Delta H$ is negative (heat leaves the system), endothermic is positive. "Feels hot" means exothermic, because heat flowed out to your hand. Breaking bonds always costs energy and forming bonds always releases it -- never reverse this.
注意符号:放热的 $\Delta H$ 为负(热离开系统),吸热的为正。"摸起来热"意味着放热,因为热流出到你手上。断键总是消耗能量,成键总是放出能量——绝不要颠倒。
An exothermic process releases heat (negative $\Delta H$, feels hot) and an endothermic one absorbs heat (positive $\Delta H$, feels cold). Breaking bonds costs energy while forming bonds releases it, and the balance of the two decides the sign of $\Delta H$.
放热过程放出热($\Delta H$ 为负,摸起来热),吸热过程吸收热($\Delta H$ 为正,摸起来凉)。断键消耗能量而成键放出能量,两者的平衡决定 $\Delta H$ 的符号。