A-Level CIE Science: Busting Common Concept Myths | A-Level CIE 科学：常见概念辨析

📚 A-Level CIE Science: Busting Common Concept Myths | A-Level CIE 科学：常见概念辨析

In A-Level CIE Science exams, many students lose marks by confusing closely related terms. This article clarifies the distinctions between commonly muddled concepts in Physics, Chemistry, and Biology, helping you avoid traps and write precise answers.

在 A-Level CIE 科学考试中，许多学生因混淆相近术语而失分。本文辨析物理、化学、生物中常见易混概念的区别，助你避开陷阱，写出精准答案。

1. Speed vs. Velocity | 速率与速度

Speed is a scalar quantity; it tells you how fast an object is moving regardless of direction. It is defined as the distance travelled per unit time: speed = distance / time.

速率是标量，只表示物体运动的快慢，不涉及方向。定义为单位时间内通过的路程：速率 = 路程 / 时间。

Velocity is a vector quantity that specifies both the magnitude (speed) and the direction of motion. It is defined as displacement per unit time: velocity = displacement / time.

速度是矢量，既包含大小（速率）又包含方向。定义为单位时间内的位移：速度 = 位移 / 时间。

For example, a car circling a roundabout at a constant speed of 30 km/h has a continuously changing velocity because its direction changes. If you confuse speed with velocity, you might incorrectly claim the car is accelerating without a change in speed.

例如，一辆车以恒定速率 30 km/h 绕环岛行驶，其速度不断改变，因为方向在变。如果混淆速率与速度，你可能错误地认为速度不变时没有加速度。

2. Mass vs. Weight | 质量与重量

Mass is the amount of matter in an object. It is a scalar quantity, measured in kilograms (kg), and does not depend on location. The mass of a textbook is the same on Earth, the Moon, or in deep space.

质量是物体所含物质的多少，是标量，单位为千克 (kg)，不随位置改变。一本书的质量在地球、月球或深空中都相同。

Weight is the gravitational force acting on an object. It is a vector quantity, measured in newtons (N), and varies with the gravitational field strength, g. Weight = mass x g (W = mg).

重量是作用在物体上的重力，是矢量，单位为牛顿 (N)，随重力场强度 g 变化。重量 = 质量 x g (W = mg)。

In exam questions, using ‘weight’ when you mean ‘mass’ can lead to unit errors and incorrect calculations. On the Moon your weight is about 1/6 of Earth, but your mass is unchanged.

考试中，误将质量写成重量会导致单位错误和计算失误。在月球上你的重量约为地球的 1/6，但质量不变。

3. Energy vs. Power | 能量与功率

Energy is the capacity to do work. It is a scalar quantity measured in joules (J). Forms include kinetic energy, gravitational potential energy, and thermal energy. The principle of conservation of energy states that energy cannot be created or destroyed, only transferred or transformed.

能量是做功的能力，是标量，单位为焦耳 (J)。形式有动能、重力势能、热能等。能量守恒定律指出，能量不能创生或消灭，只能转移或转化。

Power is the rate at which energy is transferred or work is done. It is measured in watts (W), where 1 W = 1 J/s. A device with high power does work quickly. The relationship is P = E/t or P = W/t.

功率是能量转移或做功的速率，单位为瓦特 (W)，1 W = 1 J/s。高功率设备做功能快速。关系式为 P =

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