📚 Combined Science Topic 207: Energy Stores and Transfers | 综合科学第207讲：能量储存与转移
Energy is a unifying concept across physics, chemistry, and biology. In Edexcel A-level Combined Science, topic 207 tests your ability to describe energy stores, calculate work and power, and apply conservation of energy to real systems. This article summarises key definitions, equations, and common exam pitfalls.
能量是贯穿物理、化学和生物的统一概念。在 Edexcel A-level 综合科学中，第207讲考查你描述能量储存、计算功和功率、并将能量守恒应用于实际系统的能力。本文总结关键定义、方程和常见考试误区。
1. The Seven Main Energy Stores | 七种主要能量储存
Energy is not created or destroyed; it is transferred between a small number of recognised stores. In Edexcel A-level Combined Science, you should be able to identify the store involved in a given scenario: kinetic, gravitational potential, elastic potential, thermal, chemical, nuclear, and electrostatic. For example, a stretched spring holds elastic potential energy, while a hot cup of tea stores thermal energy.
能量既不会凭空产生也不会凭空消失，它只在少数几种公认的储存形式之间转移。在 Edexcel A-level 综合科学中，你需要能够识别给定情境中涉及的能量储存：动能、重力势能、弹性势能、热能、化学能、核能和静电势能。例如，被拉伸的弹簧储存弹性势能，而一杯热茶储存热能。
- Kinetic store – any moving object.
- Gravitational potential store – an object raised above ground level.
- Elastic potential store – a stretched or compressed spring.
- Thermal store – all objects above absolute zero.
- Chemical store – fuels, food, and batteries.
- Nuclear store – atomic nuclei.
- Electrostatic store – separated positive and negative charges.
动能储存——任何运动的物体；重力势能储存——被举高到地面以上的物体；弹性势能储存——被拉伸或压缩的弹簧；热能储存——所有高于绝对零度的物体；化学能储存——燃料、食物和电池；核能储存——原子核；静电势能储存——分离的正负电荷。
2. Work Done and Kinetic Energy | 做功与动能
ne in joules (J), F is force in newtons (N), and d is distance moved in metres (m). When work is done on an object, its kinetic energy usually increases.
当力使物体沿力的方向移动时，就做了功。做的功等于转移的能量。功的计算使用方程 W = F × d，其中 W 是做功，单位为焦耳 (J)；F 是力，单位为牛顿 (N)；d 是移动距离，单位为米 (m)。当对物体做功时，物体的动能通常会增加。
KE = ½ × m × v²
Kinetic energy (KE) is the energy of a moving object. In the equation, m is mass in kilograms (kg) and v is speed in metres per second (m/s). Note that speed is squared, so doubling the speed quadruples the kinetic energy.
动能 (KE) 是运动物体的能量。方程中 m 是质量，单位为千克 (kg)；v 是速度，单位为米每秒 (m/s)。注意速度被平方，因此速度加倍时动能变为原来的四倍。
3. Gravitational Potential Energy | 重力势能
avity stores gravitational potential energy (GPE). The amount of GPE depends on the object' he height gained. Edexcel uses g = 9.8 m/s² on Earth unless the question states otherwise.
任何被克服重力抬升的物体都会储存重力势能 (GPE)。GPE 的大小取决于物体的质量、重力场强度和上升高度。除非题目另有说明，Edexcel 在地球表面使用 g = 9.8 m/s²。
GPE = m × g × h
In this equation, m is mass in kg, g is gravitational field strength in N/kg, and h is height in metres. The unit of GPE is the joule (J). Energy lost from the GPE store during a fall is transferred to the kinetic store.
在这个方程中，m 是质量 (kg)，g 是重力场强度 (N/kg)，h 是高度 (m)。GPE 的单位是焦耳 (J)。下落过程中 GPE 储存的能量会转移到动能储存中。
4. Power and Efficiency | 功率与效率
shorter time has a higher power rating. Power is measured in watts (W), where 1 W = 1 J/s.
功率是能量转移或做功的速率。在更短时间内转移相同能量的设备具有更高的功率额定值。功率的单位是瓦特 (W)，其中 1 W = 1 J/s。
P = E / t and P = W / t
Efficiency compares useful energy output with total energy input. No real device is 100% efficient because some energy is always dissipated as heat due to friction or resistance. Efficiency can be expressed as a decimal or as a percentage.
效率将有用的能量输出与总能量输入进行比较。没有任何真实设备能达到 100% 效率，因为总有一些能量因摩擦或电阻以热的形式耗散。效率可以表示为小数或百分比。
Efficiency = Useful output energy / Total input energy × 100%
5. Conservation of Energy | 能量守恒
The principle of conservation of energy states that energy cannot be created or destroyed, only transferred from one store to another. In a closed system, the total energy before an event is equal to the total energy after the event. This principle is used to predict speeds, heights, and temperatures in exam questions.
能量守恒定律指出，能量既不能凭空产生也不能凭空消失，只能从一种储存转移到另一种储存。在封闭系统中，事件发生前的总能量等于事件发生后的总能量。该原理在考试题中用于预测速度、高度和温度。
before impact. Therefore, m × g × h = ½ × m × v². Mass cancels out, giving v² = 2 × g × h.
示例：一个球从 2.0 m 高处落下。忽略空气阻力，最高点的 GPE 在撞击前完全转化为 KE。因此，m × g × h = ½ × m × v²。质量可以约去，得到 v² = 2 × g × h。
6. Energy Transfers in Chemical Reactions | 化学反应中的能量转移
In chemistry, energy changes occur when bonds are broken and new bonds are formed. Breaking bonds requires energy (endothermic), while making bonds releases energy (exothermic). The difference between the energy absorbed and released determines whether the overall reaction is exothermic or endothermic.
在化学中，当化学键断裂和新化学键形成时会发生能量变化。断裂化学键需要吸收能量（吸热过程），而形成化学键会释放能量（放热过程）。吸收的能量与释放的能量之间的差值决定了总反应是放
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