📚 Year 7 CIE Physics Unit Test Mock Paper Walkthrough | 七年级CIE物理单元测试模拟卷解析
Welcome to this detailed walkthrough of a typical Year 7 CIE Physics unit test mock paper. The questions have been designed to mirror the style and content of a real end‑of‑unit assessment, covering measurement, forces, energy, electricity, waves and space. Each section presents a sample question, explains the correct answer, clarifies common mistakes and reinforces the key concepts you need to master. Use this guide to identify your strengths and fill any gaps before the actual test.
欢迎阅读这份典型的七年级CIE物理单元测试模拟卷的详细解析。题目模拟了真实单元评估的风格与内容，涵盖测量、力、能量、电学、波动和太空等主题。每个小节给出一道例题，解释正确答案，分析常见错误并巩固必须掌握的核心概念。利用本指南找出自己的优势，并在正式考试前弥补短板。
1. Measurements and Units | 测量与单位
Question: A student uses a ruler to measure the length of a pencil as 0.18 m. Express this length in millimetres. Which piece of apparatus is most suitable for measuring exactly 25 cm³ of water?
题目：一名学生用直尺测得铅笔的长度为 0.18 m。请用毫米表示该长度。要精确量取 25 cm³ 的水，最适合的仪器是什么？
To convert metres to millimetres, multiply by 1000 because 1 m = 1000 mm. Therefore 0.18 m × 1000 = 180 mm. Always check the scale: going from a larger unit to a smaller unit means the number becomes larger. For measuring an accurate volume of liquid, a measuring cylinder is the correct choice. A beaker gives only a rough estimate, whereas a measuring cylinder has a fine scale graduated in cm³ or ml (1 cm³ = 1 ml).
将米转换为毫米要乘以 1000，因为 1 m = 1000 mm。因此 0.18 m × 1000 = 180 mm。始终注意单位尺度：从大单位转为小单位，数值会变大。要精确量取液体体积，应使用量筒。烧杯只能粗略估计，而量筒上标有以 cm³ 或 ml 为单位的精密刻度（1 cm³ = 1 ml）。
Common mistake: misplacing the decimal point when converting. A good trick is to remember that ‘milli-‘ means one‑thousandth, so 1 m contains 1000 mm. Students also often confuse cm³ with ml, but they are equivalent for water and water‑based solutions at room temperature.
常见错误：换算时点错小数点。一个好方法是记住“毫”表示千分之一，因此 1 m 包含 1000 mm。学生还常把 cm³ 和 ml 弄混，但在室温下的水和水溶液中它们是等同的。
2. Mass and Weight | 质量与重量
Question: An astronaut has a mass of 72 kg on Earth. What is her mass on the Moon? Explain why her weight would be different on the Moon.
题目：一名宇航员在地球上的质量为 72 kg。她在月球上的质量是多少？解释为什么她在月球上的重量会不同。
Mass is the amount of matter in an object; it does not change with location. Therefore the astronaut’s mass on the Moon is still 72 kg. Weight, however, is the pull of gravity on that mass. The Moon’s gravitational field strength is about one‑sixth of Earth’s, so her weight on the Moon is about one‑sixth of her Earth weight. On Earth, weight = mass × 10 N/kg (approximately 10 m/s²), giving 720 N. On the Moon, weight ≈ 72 kg × 1.6 N/kg ≈ 115 N.
质量是物体所含物质的多少，不随位置改变。因此宇航员在月球上的质量仍然是 72 kg。而重量是作用在该质量上的引力。月球表面的引力场强度约为地球的六分之一，所以她月球上的重量约为地球上重量的六分之一。在地球上，重量 = 质量 × 10 N/kg（约 10 m/s²），得 720 N。在月球上，重量 ≈ 72 kg × 1.6 N/kg ≈ 115 N。
Mass is measured in kilograms (kg) using a beam balance or digital balance. Weight is a force, so it is measured in newtons (N) using a spring balance or force metre. A common confusion is thinking a person ‘weighs 72 kg’; the correct statement is ‘has a mass of 72 kg’ and ‘weighs about 720 N on Earth’.
质量用千克（kg）表示，可用杠杆天平或电子天平测量。重量是力，因此用牛顿（N）表示，使用弹簧秤或测力计测量。一个常见的误区是说一个人“重 72 kg”；准确的说法是“质量为 72 kg”，而“在地球上重约 720 N”。
3. Density | 密度
Question: A metal block has a mass of 300 g and a volume of 60 cm³. Calculate its density. Will the block float or sink in water? Explain.
题目：一块金属的质量为 300 g，体积为 60 cm³。计算它的密度。该金属块在水中会浮起还是下沉？请解释。
Density is mass per unit volume. Use the formula:
density = mass ÷ volume
Plugging in the values: density = 300 g ÷ 60 cm³ = 5 g/cm³. The density of water is 1 g/cm³. Since 5 g/cm³ is greater than 1 g/cm³, the block will sink. An object floats only if its density is less than the density of the liquid.
密度是单位体积的质量。使用公式：
密度 = 质量 ÷ 体积
代入数值：密度 = 300 g ÷ 60 cm³ = 5 g/cm³。水的密度为 1 g/cm³。由于 5 g/cm³ 大于 1 g/cm³，金属块会下沉。只有当物体的密度小于液体密度时它才会浮起。
Common mistakes include mixing up mass and weight or forgetting to use the correct units. The density of a material does not change if you cut the block in half – each half still has a density of 5 g/cm³ because mass and volume are both halved, so their ratio stays the same.
常见错误包括混淆质量与重量，或忘记使用正确的单位。如果将金属块切成两半，密度并不改变——每一半的密度仍为 5 g/cm³，因为质量和体积都减半，其比值保持不变。
4. Forces and Motion | 力与运动
Question: A cyclist stops pedalling and gradually slows down on a flat road. Name the forces that cause the bicycle to decelerate. What would happen if those forces suddenly disappeared?
题目：一位骑行者停止踩踏，在平直道路上逐渐减速。说出使自行车减速的力。如果这些力突然消失会怎样？
The main opposing forces are friction between the tyres and the road, and air resistance (drag) pushing against the cyclist. There may also be friction in the bearings. These forces act in the direction opposite to motion, causing deceleration. If all opposing forces disappeared, the bicycle would continue moving at a constant speed in a straight line – this is an example of Newton’s first law of motion (inertia).
主要的阻碍力是轮胎与路面间的摩擦力，以及作用在骑行者身上的空气阻力（拖拽力）。轴承中也可能存在摩擦。这些力与运动方向相反，导致减速。如果所有阻碍力突然消失，自行车将沿直线保持匀速运动——这是牛顿第一运动定律（惯性）的体现。
In Year 7, it is enough to know that unbalanced forces change an object’s speed or direction. Balanced forces produce no change in motion. When the cyclist was pedalling, the driving force balanced the friction and air resistance; once the driving force is removed, the remaining forces are unbalanced, causing the bicycle to slow.
在七年级阶段，知道不平衡的力会改变物体的速度或方向就够了。平衡的力不改变运动状态。骑行者踩踏时，驱动力与摩擦和空气阻力平衡；一旦驱动力撤去，剩余力不平衡，自行车就会减速。
5. Speed, Distance and Time | 速度、距离与时间
Question: A car travels 180 km in 2 hours 30 minutes. Calculate its average speed in km/h. Then convert the speed to m/s.
题目：一辆汽车在 2 小时 30 分钟内行驶了 180 km。计算其平均速度（单位：km/h），再将速度换算为 m/s。
average speed = total distance ÷ total time
Convert 2 h 30 min to hours: 30 min = 0.5 h, so total time = 2.5 h. Average speed = 180 km ÷ 2.5 h = 72 km/h. To convert km/h to m/s, note that 1 km = 1000 m and 1 h = 3600 s. Thus divide by 3.6: 72 ÷ 3.6 = 20 m/s.
平均速度 = 总距离 ÷ 总时间。将 2 小时 30 分钟化为小时：30 min = 0.5 h，总时间为 2.5 h。平均速度 = 180 km ÷ 2.5 h = 72 km/h。将 km/h 换算为 m/s，注意 1 km = 1000 m，1 h = 3600 s。因此除以 3.6：72 ÷ 3.6 = 20 m/s。
average speed = total distance ÷ total time
A typical mistake is taking the average of two speeds, e.g. (60 + 80) ÷ 2, without considering the time spent at each speed. Always use total distance and total time. Also remember the conversion factor: m/s = km/h ÷ 3.6.
常见错误是直接求两个速度的平均值，比如 (60 + 80) ÷ 2，而不考虑每个速度耗时。必须使用总距离和总时间。还要记住换算因子：m/s = km/h ÷ 3.6。
6. Energy Forms and Transfers | 能量形式与转化
Question: In a battery‑powered torch, name the main energy changes that occur from the battery to the light emitted. State the principle of conservation of energy.
题目：在一个电池供电的手电筒中，说出从电池到发出光的主要能量变化。表述能量守恒原理。
The chemical energy stored in the battery is converted into electrical energy in the circuit. The electrical energy then flows to the bulb, where it is mostly transformed into light energy and some wasted thermal (heat) energy. Energy is never created or destroyed; it is only converted from one form to another. This is the principle of conservation of energy.
电池中储存的化学能转化为电路中的电能。电能流到灯泡，在那里大部分转化为光能，同时有部分废热（热）能散失。能量既不能创生也不能消灭，只能从一种形式转化为另一种形式。这就是能量守恒原理。
Useful energy transfers: chemical → electrical → light. Sankey diagrams or energy flow arrows help to show these conversions. In Year 7, you should be able to identify input and output energies for simple devices like a heater (electrical → thermal) or a solar panel (light → electrical). Remember that some energy is always transferred to the surroundings, usually as heat, which is why no device is 100% efficient.
有用的能量转化：化学能 → 电能 → 光能。桑基图或能量流向箭头可帮助展示这些转化。在七年级，你应能识别简单设备的输入和输出能量，例如电暖器（电能 → 热能）或太阳能电池板（光能 → 电能）。记住一部分能量总是转移到环境，通常以热的形式，所以没有任何设备是 100% 高效的。
7. Electric Circuits | 电路
Question: A student builds a series circuit containing one cell, a switch and two lamps. All components are connected one after another. What happens to the second lamp if the first lamp burns out? Name two materials that are good electrical conductors.
题目：一名学生搭建了一个包含一节电池、一个开关和两只灯泡的串联电路，所有元件依次连接。如果第一只灯泡烧坏，第二只灯泡会发生什么？说出两种良好的导电材料。
In a series circuit, there is only one path for the current. If one lamp burns out (the filament breaks), the circuit is broken; current stops flowing everywhere, and the second lamp goes out as well. Good conductors include metals such as copper and aluminium. Conductors have free electrons that move easily, allowing current to pass. Insulators, like plastic and rubber, do not allow current to flow through them easily and are used to coat wires for safety.
在串联电路中，电流只有一条通路。如果一只灯泡烧坏（灯丝断开），电路断开，电流在所有地方都停止，第二只灯泡也会熄灭。良好的导体包括铜和铝等金属。导体有易于移动的自由电子，允许电流通过。绝缘体，如塑料和橡胶，不易让电流通过，被用来包裹电线以保证安全。
Circuit symbols must be drawn clearly: a cell is a long thin line and a short thick line (+ and −), a lamp is a circle with a cross inside, and a switch is a break in the line that can be closed. Many students forget that in a series circuit, the same current passes through all components. If the cell voltage is increased, the current through each lamp increases (assuming resistance is constant), making them brighter – but this can also cause the lamp to blow.
电路符号必须清晰画出：电池是一个细长线和一个粗短线（正负极），灯泡是里面有一个叉的圆圈，开关是线上可闭合的缺口。许多学生忘了在串联电路中，流过所有元件的电流相同。如果电池电压增大，流过每只灯泡的电流增大（假设电阻恒定），灯泡变亮——但这也可能导致灯泡烧毁。
8. Sound | 声音
Question: A loudspeaker produces a sound of frequency 500 Hz. Describe how the sound travels to a listener’s ear and explain why the sound cannot be heard in a vacuum.
题目：一个扬声器发出频率为 500 Hz 的声音。描述声音如何传到听者的耳朵，并解释为什么在真空中听不到声音。
Sound is produced by vibrations. The loudspeaker cone vibrates, compressing and stretching the surrounding air particles. These compressions and rarefactions travel through the air as a longitudinal wave until they reach the ear, causing the eardrum to vibrate. Sound cannot travel through a vacuum because there are no particles to vibrate and pass on the energy. In space, where there is a vacuum, an explosion would be silent.
声音由振动产生。扬声器纸盆振动，压缩和拉伸周围的空气粒子。这些疏密变化以纵波的形式通过空气传播，直到到达耳朵，使鼓膜振动。声音不能在真空中传播，因为没有粒子可以振动并传递能量。在太空的真空中，爆炸将是无声的。
The pitch of a sound depends on its frequency: a higher frequency means a higher‑pitched sound. Loudness depends on the amplitude of the vibration: a larger amplitude produces a louder sound. On an oscilloscope trace, a high‑pitched sound has many waves across the screen, while a loud sound has tall waves. Common misconception: thinking that higher frequency means louder sound.
音调的高低取决于频率：频率越高，音调越高。响度取决于振动幅度：振幅越大，声音越响。在示波器显示器上，高音调声音的波形密集，而响亮的声音波形幅度大。常见误解：认为频率越高声音越响。
9. Earth and the Solar System | 地球与太阳系
Question: List the eight planets in order of increasing distance from the Sun. Name the force that keeps the planets in orbit.
题目：按距离太阳由近到远的顺序列出八大行星。说出使行星保持在轨道上运行的力。
The correct order is: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Many students use a mnemonic such as ‘My Very Easy Method Just Speeds Up Naming’. The force that holds the planets in orbit is gravity. The Sun’s huge mass exerts a gravitational pull on each planet, constantly pulling them inward and preventing them from flying off in a straight line.
正确的顺序是：水星、金星、地球、火星、木星、土星、天王星、海王星。许多学生使用口诀记忆，如“水金地火木土天海”。使行星保持在轨道上运行的力是万有引力。太阳巨大的质量对每颗行星施加引力，不断将行星向内拉，防止它们沿直线飞离。
Gravity also explains why the Moon orbits the Earth, and why satellites orbit planets. The orbit is a balance between the planet’s forward motion and the inward pull of gravity. Without gravity, all planets would travel in straight lines out of the solar system. The Sun is a star at the centre of our solar system; it produces light and heat through nuclear fusion, though this detail is beyond Year 7.
万有引力也解释了为什么月球绕地球转、以及卫星绕行星转。轨道是行星前进运动与向内引力之间的平衡。没有引力，所有行星都会沿直线飞出太阳系。太阳是恒星，位于太阳系中心，通过核聚变产生光和热，不过这一细节超出了七年级范围。
10. Light and Shadows | 光与影子
Question: A small opaque ball is placed between a point light source and a screen. Explain how a shadow is formed and describe the appearance of the shadow on the screen. What happens to the shadow if the ball is moved closer to the light source?
题目：将一个不透明小球放在点光源和屏幕之间。解释影子是如何形成的，并描述屏幕上影子的外观。如果把球移近光源，影子会有何变化？
Light travels in straight lines. When the opaque ball blocks the light rays, an area of darkness – a shadow – forms on the screen. Because the source is a point, the shadow has a sharp edge and is a dark circle (umbra). If the ball moves closer to the light source, more light rays are blocked, so the shadow becomes larger on the screen. This is similar to how a hand closer to a torch casts a bigger shadow puppet.
光沿直线传播。当不透明小球阻挡光线时，屏幕上形成一片黑暗区域——影子。由于是点光源，影子边缘锐利，呈现一个深暗的圆圈（本影）。如果把球移近光源，被阻挡的光线更多，屏幕上的影子会变大。这就像手靠近手电筒时，手影会变大一样。
Materials are classified as transparent (allow light to pass through clearly, e.g. clear glass), translucent (allow some light to scatter, e.g. frosted glass) and opaque (block light completely, e.g. wood). A shadow needs a light source, an opaque object and a screen. Common error: thinking the shadow is the object’s reflection; a shadow is an absence of light, not a reflection.
材料可分为透明（光线清晰穿过，如透明玻璃）、半透明（部分光散射，如毛玻璃）和不透明（完全阻挡光线，如木头）。形成影子需要光源、不透明物体和屏幕。常见错误：以为影子是物体的反射；影子其实是光照缺失，而非反射。
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