📚 GCSE CIE Physics: Key Concept Comparisons | GCSE CIE 物理：知识点对比
Physics is full of pairs of terms that sound similar but carry distinct meanings – confusing them can cost marks in your CIE exams. This article clarifies the most important conceptual comparisons you will meet in the GCSE syllabus, helping you use the right words and ideas with confidence.
物理学中有许多听起来相似但含义不同的概念对，混淆它们可能会在 CIE 考试中失分。本文厘清了您在 GCSE 课程中会遇到的最重要的概念对比，帮助您自信地使用正确的词汇和思路。
1. Scalars and Vectors | 标量与矢量
A scalar quantity has only magnitude (size). Mass, temperature, distance, speed and energy are all scalars.
标量只有大小（数值）。质量、温度、距离、速率和能量都是标量。
A vector quantity has both magnitude and direction. Force, velocity, displacement, weight and momentum are typical vectors.
矢量既有大小又有方向。力、速度、位移、重量和动量是典型的矢量。
Scalars can be added using ordinary arithmetic. Vectors must be added by taking direction into account, often using the tip-to-tail or parallelogram method.
标量可以直接用算术相加。矢量相加必须考虑方向，通常使用三角形法或平行四边形法。
On a diagram, a vector is drawn as an arrow: the length represents the magnitude and the arrowhead shows the direction.
在图上，矢量用箭头表示：长度代表大小，箭头代表方向。
When a car changes direction at a constant speed, its speed stays the same (scalar) but its velocity changes (vector).
当汽车以恒定速率改变方向时，其速率（标量）不变，但其速度（矢量）发生变化。
2. Mass and Weight | 质量与重量
Mass is the quantity of matter in an object. It is a scalar measured in kilograms (kg) and does not depend on location.
质量是物体所含物质的多少。它是标量，以千克为单位，与所在位置无关。
Weight is the gravitational force acting on an object. It is a vector measured in newtons (N) and is calculated using W = m × g, where g is the gravitational field strength.
重量是作用在物体上的万有引力。它是矢量，以牛顿为单位，计算公式为 W = m × g，其中 g 是引力场强。
On Earth, g ≈ 9.8 m/s², so a 10 kg object has a weight of about 98 N. On the Moon, g ≈ 1.6 m/s², so the same object weighs only 16 N but its mass is still 10 kg.
在地球上，g ≈ 9.8 m/s²，因此一个 10 kg 的物体重约 98 N。在月球上，g ≈ 1.6 m/s²，同一物体仅重 16 N，但其质量仍为 10 kg。
A beam balance compares masses, while a newton metre (spring balance) measures weight directly.
托盘天平比较质量，而牛顿计（弹簧测力计）直接测量重量。
3. Speed and Velocity | 速率与速度
Speed is the rate at which distance is covered. It is a scalar quantity given by average speed = total distance ÷ total time.
速率是距离随时间的变化率。它是标量，平均速率 = 总距离 ÷ 总时间。
Velocity is the rate of change of displacement. It is a vector: average velocity = displacement ÷ time, and the direction must be stated.
速度是位移的变化率。它是矢量：平均速度 = 位移 ÷ 时间，并且必须说明方向。
An athlete running once around a 400 m track at constant speed has an average speed of, say, 8 m/s, but her displacement after one lap is zero, so her average velocity is 0 m/s.
一名运动员以恒定速率绕 400 米跑道跑完一圈，假设平均速率为 8 m/s，但一圈后位移为零，因此平均速度为 0 m/s。
Even when the speedometer shows a steady number, turning a corner means velocity is changing because direction changes.
即使速度表显示的数字保持不变，转弯时速度也在变化，因为方向发生了变化。
4. Heat and Temperature | 热量与温度
Temperature is a measure of the average kinetic energy of the particles in a substance. It is a scalar, measured in degrees Celsius (°C) or kelvin (K).
温度是物质内粒子平均动能的量度。它是标量，以摄氏度 (°C) 或开尔文 (K) 为单位。
Heat is the transfer of thermal energy from a region of higher temperature to a region of lower temperature. It is energy in transit and is measured in joules (J).
热量是热能从较高温区向较低温区的转移。它是传递中的能量，以焦耳 (J) 为单位。
An object does not ‘contain’ heat; it possesses internal energy. You can increase an object’s internal energy by heating it or by doing work on it.
物体并不“包含”热量；它拥有内能。通过加热或对物体做功可以增加其内能。
During melting or boiling, the temperature stays constant even though the substance is absorbing heat – the energy goes into breaking bonds rather than increasing kinetic energy.
在熔化或沸腾过程中，尽管物质在吸收热量，温度却保持不变——因为能量用于打破键，而不是增加动能。
5. Evaporation and Boiling | 蒸发与沸腾
Evaporation is a surface phenomenon that can occur at any temperature. The fastest-moving particles escape from the liquid surface, cooling the remaining liquid.
蒸发是一种表面现象，可在任何温度下发生。运动最快的粒子从液体表面逸出，使剩余液体冷却。
Boiling happens throughout the liquid at a fixed temperature – the boiling point. Bubbles of vapour form throughout and rise to the surface.
沸腾发生在整个液体中，需要在固定的温度——沸点下进行。整个液体内形成气泡并上升到表面。
The rate of evaporation increases with temperature, surface area and air movement, and decreases with humidity.
蒸发速率随温度、表面积和空气流动的增大而加快，随湿度增大而减慢。
The boiling point of a liquid depends on the external pressure: at higher altitudes, atmospheric pressure is lower, so water boils at a temperature below 100 °C.
液体的沸点取决于外部压强：在高海拔地区，大气压较低，因此水在低于 100 °C 时沸腾。
6. Series and Parallel Circuits | 串联与并联电路
In a series circuit, components are connected one after another, so there is only a single path for the current. The current is the same everywhere.
在串联电路中，元件一个接一个地连接，电流只有一条通路。各处电流相同。
In a parallel circuit, components are connected on separate branches, giving the current multiple paths. The total current from the source splits at a junction and recombines later.
在并联电路中，元件连接在独立的分支上，电流有多条通路。来自电源的总电流在节点分流，之后再汇合。
In series, the total resistance R = R₁ + R₂ + … and is larger than any single resistor. In parallel, 1/R = 1/R₁ + 1/R₂ + … and the combined resistance is always less than the smallest branch resistance.
串联电路中，总电阻 R = R₁ + R₂ + …，且大于任何一个电阻。并联电路中，1/R = 1/R₁ + 1/R₂ + …，总电阻始终小于最小分支电阻。
Voltage divides across series components (potential divider effect), whereas in parallel each branch gets the full source voltage.
电压在串联元件上分配（分压效应），而在并联电路中每个支路都获得全部电源电压。
If one component in a series circuit fails, the whole circuit stops working. In a parallel circuit, other branches can continue to work.
如果串联电路中一个元件损坏，整个电路停止工作。在并联电路中，其他支路可以继续工作。
7. Reflection and Refraction | 反射与折射
Reflection occurs when a wave bounces off a surface. The angle of incidence equals the angle of reflection, with both angles measured from the normal (a line perpendicular to the surface).
反射发生在波从表面弹回时。入射角等于反射角，两者均从法线（垂直于表面的线）量起。
Refraction is the bending of a wave as it crosses the boundary between two media, caused by a change in wave speed.
折射是波穿过两种介质间的交界面时因波速改变而发生的弯曲。
When light goes from air into glass (optically denser), it slows down and bends towards the normal. Going from glass into air, it speeds up and bends away from the normal.
光从空气进入玻璃（光密介质）时速度减慢，向法线偏折。从玻璃进入空气时速度加快，偏离法线。
Total internal reflection can happen when light tries to move from a denser medium to a less dense one at an angle of incidence greater than the critical angle. This principle is used in optical fibres.
当光试图从光密介质进入光疏介质，且入射角大于临界角时，可发生全内反射。这一原理用于光纤。
8. Kinetic Energy and Gravitational Potential Energy | 动能与重力势能
Kinetic energy (Eₖ) is the energy an object possesses because of its motion. It is a scalar, given by Eₖ = ½ m v², where m is mass and v is speed.
动能 (Eₖ) 是物体由于运动而具有的能量。它是标量，公式为 Eₖ = ½ m v²，其中 m 为质量，v 为速率。
Gravitational potential energy (Eₚ) is the energy stored in an object due to its height above a reference level. Eₚ = m g h, where h is the height and g is gravitational field strength.
重力势能 (Eₚ) 是物体因高于参考水平面而储存的能量。Eₚ = m g h，其中 h 是高度，g 是引力场强。
Both are measured in joules (J) and are forms of mechanical energy. In many situations, energy converts between kinetic and potential forms (e.g. a swinging pendulum or a falling object).
两者均以焦耳 (J) 为单位，都是机械能的形式。在许多情况下，能量在动能和势能之间相互转化（如摆动的钟摆或下落的物体）。
In the absence of air resistance, the total mechanical energy (Eₖ + Eₚ) remains constant, illustrating the principle of conservation of energy.
在没有空气阻力的情况下，总机械能 (Eₖ + Eₚ) 保持恒定，体现了能量守恒定律。
9. Work and Power | 功与功率
Work is done when a force moves an object through a distance in the direction of the force. Work = force × distance (W = F × d) and is measured in joules (J).
当一个力使物体沿着力的方向移动一段距离时，就做了功。功 = 力 × 距离 (W = F × d)，单位为焦耳 (J)。
Power is the rate at which work is done or the rate of energy transfer. Power = work done ÷ time (P = W / t), and the unit is the watt (W), where 1 W = 1 J/s.
功率是做功或能量转换的速率。功率 = 做功 ÷ 时间 (P = W / t)，单位是瓦特 (W)，1 W = 1 J/s。
If you lift a heavy box slowly or quickly, the work done against gravity is the same, but the faster you lift, the higher the power output.
无论缓慢还是快速地提起重箱子，克服重力所做的功是相同的，但提起得越快，输出的功率就越大。
A machine that transfers a large amount of energy in a short time has a high power rating. For example, a 2000 W kettle transfers energy much faster than a 20 W lamp.
在短时间内传输大量能量的机器功率较高。例如，2000 W 的电热水壶传输能量的速度远快于 20 W 的灯泡。
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