📚 Common Misconceptions in Year 7 CIE Physics and How to Correct Them | Year 7 CIE 物理常见误区与纠正方法
Physics in Year 7 introduces many new concepts, and it is easy to pick up misunderstandings that can affect later learning. This article highlights the most common misconceptions in the CIE Physics curriculum and provides clear corrections to help you build a solid foundation. Each section explains the mistake in simple English followed by the correct idea in Chinese, so you can master both the language and the science.
Year 7 物理引入许多新概念，学生很容易产生一些误解，这些误解会影响后续学习。本文指出 CIE 物理课程中最常见的误区，并给出清晰的纠正方法，帮助你打下扎实的基础。每个小节先用英文解释误区，再用中文阐明正确概念，让你同时掌握学科英语和科学原理。
1. Mass vs Weight | 质量与重量误区
Many students think mass and weight are the same thing. They often use a spring balance to measure mass and say the weight is '50 kilograms'. They also believe mass can change when you go to the Moon.
许多学生认为质量和重量是一回事。他们经常用弹簧秤来测质量，并说重量是 "50 千克"。他们还认为到了月球上质量会改变。
In physics, mass is the amount of matter in an object. It is measured in kilograms (kg) using a beam balance and does not change with location. Weight is the force of gravity pulling on the mass; its unit is the newton (N). You measure weight with a spring balance. The relationship is:
weight (N) = mass (kg) × gravitational field strength (N/kg)
物理中，质量是物体所含物质的多少，单位是千克 (kg)，用天平测量，不随位置变化。重量是地球对物体的引力，单位是牛顿 (N)，用弹簧秤测量。两者的关系是：重量 (N) = 质量 (kg) × 重力场强度 (N/kg)。
On Earth, the gravitational field strength is about 10 N/kg. So a 60 kg person weighs 600 N. On the Moon, the field strength is only 1.6 N/kg, so the person still has a mass of 60 kg but weighs just 96 N. Your mass never changes unless you gain or lose matter; your weight depends on where you are.
在地球上，重力场强度约为 10 N/kg，因此一个 60 kg 的人重 600 N。在月球上，重力场强度只有 1.6 N/kg，所以这个人的质量仍是 60 kg，但重量仅为 96 N。质量除非你增加或减少物质，否则永不改变；重量则取决于你所在的位置。
2. Speed vs Acceleration | 速度与加速度误区
Students often say 'the car is accelerating, so its speed must be very high'. They think speed and acceleration are the same, or that a fast-moving object must have a large acceleration.
学生常说 "汽车在加速，它的速度一定很快"。他们认为速度和加速度是一样的，或者运动快的物体加速度一定很大。
Speed is a measure of how fast something moves: distance travelled per unit time. Acceleration is the rate at which velocity changes. The formula for average acceleration is:
acceleration = change in velocity ÷ time taken
速度是描述物体运动快慢的量：单位时间内通过的距离。加速度是速度变化的快慢。平均加速度的公式是：加速度 = 速度变化量 ÷ 时间。
If a car travels at a steady 100 km/h in a straight line, its speed is high but its acceleration is zero because the velocity is not changing. If a rocket takes off from rest and quickly increases its speed, it has a large acceleration even though its speed at the first instant may be small.
如果一辆车以 100 km/h 匀速直线行驶，它的速度很大，但加速度为零，因为速度没有改变。如果火箭从静止起飞并迅速加快，它的加速度很大，即使初时刻速度很小。
3. Force and Motion | 力与运动误区
A common belief is that a force is needed to keep an object moving. Many think that if no force acts on a moving ball, it will stop by itself. This comes from everyday experience where friction slows things down.
一个普遍的误解是：物体运动需要力来维持。许多人认为，如果不对运动的球施加力，它会自己停下来。这源于日常经验中摩擦力使物体减速的现象。
According to Newton's First Law, an object will stay at rest or move in a straight line at a constant speed if the forces on it are balanced (or if there is no net force). It is unbalanced force that causes a change in motion – that is, acceleration or deceleration.
根据牛顿第一定律，若作用在物体上的力平衡（或没有净外力），物体将保持静止或匀速直线运动状态。正是不平衡的力引起了运动状态的改变——即加速或减速。
When you kick a football, the force of your boot accelerates it. Once in the air, friction and air resistance are unbalanced forces that slow it down. If there were no friction at all, the ball would keep moving forever at constant speed.
当你踢足球时，脚的力使它加速。一旦离开脚，摩擦力和空气阻力成为不平衡力，使其减速。如果没有摩擦力，球将永远匀速运动下去。
4. Current and Voltage | 电流与电压误区
Many learners think electric current gets 'used up' as it flows around a circuit, so the current is smaller after passing through a lamp. They also confuse voltage with current, saying 'voltage flows through the wires'.
许多学生认为电流在电路中流动时会被 "用掉"，因此经过灯泡后电流会变小。他们还混淆电压与电流，说 "电压在电线中流动"。
Electric current is the rate of flow of charge; it is not consumed. In a series circuit, the current is the same everywhere – the same number of charges pass per second at any point. Voltage (potential difference) is the 'push' that drives the current around. It is measured across a component, not through it.
电流是电荷流动的速率，并不会被消耗。在串联电路中，各处的电流都相等——每秒通过任何点的电荷数相同。电压（电势差）是推动电流流动的 "推力"，测量的是元件两端的电压，而不是流经元件的电压。
Think of a water analogy: current is like the flow rate of water in a pipe, while voltage is like the pressure difference from a pump or height difference. The water is not used up, just as charge is conserved. A battery provides a voltage rise, and the potential difference across a lamp causes it to light.
可以用水流作类比：电流如同水管中的水流速率，电压则像水泵提供的压力差或高度差。水并没有被用光，同样电荷是守恒的。电池提供一个电压，灯泡两端的电势差使其发光。
5. Heat and Temperature | 热量与温度误区
Students often treat heat and temperature as the same. They say 'a large bowl of warm water has more heat than a small cup of boiling water'. They also think that when two objects reach the same temperature, they contain the same amount of heat.
学生常把热量和温度混为一谈。他们说 "一大碗温水比一小杯沸水有更多热量"。他们还认为当两个物体温度相同时，它们所含的热量也相等。
Temperature is a measure of how hot or cold an object is – it tells us the average kinetic energy of its particles. Heat is the energy transferred from a hotter object to a colder one because of the temperature difference. Objects do not contain 'heat'; they contain internal energy.
温度是衡量物体冷热程度的物理量，它反映了粒子平均动能的大小。热量是由于温度差而从高温物体传递到低温物体的能量。物体并不 "含有热量"；它们含有内能。
A large bowl of water at 60 °C has more internal energy than a small cup at 60 °C because it has many more particles, even though their temperature is the same. When two items reach the same temperature, thermal equilibrium is reached, but their internal energies can still be very different.
一大碗 60 °C 的水比一小杯 60 °C 的水含有更多内能，因为它的粒子数量多得多，尽管温度相同。当两个物体达到相同温度时，它们达到了热平衡，但它们的内能可能仍然相差很大。
6. Energy Cannot Be 'Used Up' | 能量不会被 "用完"
A very common misconception is that energy is 'used up' or 'disappears' when a device runs. For example, 'the lamp used up all the electrical energy'. This goes against the principle of conservation of energy.
一个非常普遍的误区是：能量在使用设备时被 "用光" 或 "消失" 了。例如，"电灯用完了所有的电能"。这违背了能量守恒定律。
Energy is never destroyed; it is transferred from one store to another. In a lamp, electrical energy is transferred to light energy and thermal energy (which spreads into the surroundings). The total energy before and after remains exactly the same, though some has become less useful.
能量永远不会被消灭；它从一种储存形式转移到另一种。在电灯中，电能转移为光能和热能（散布到周围环境中）。转移前后的总能量完全相等，尽管部分能量变得不太有用了。
When you rub your hands together, mechanical energy is transferred to thermal energy, warming your skin. No energy has been destroyed. The idea that energy is 'lost' really means it has spread out as heat that we can no longer use easily.
当你搓手时，机械能转移为热能，温暖了皮肤。没有能量被消灭。所谓能量 "损耗" 实际上是指能量以热能形式散逸，无法再方便地利用。
7. Light Reflection and Refraction | 光的反射与折射误区
Students often draw the angle of incidence between the incident ray and the mirror surface, not the normal. They may think light always travels in straight lines no matter what, and that when light refracts, the ray bends in a random direction.
学生画入射角时常画入射线与镜面的夹角，而不是与法线的夹角。他们认为光在任何情况下都沿直线传播，折射时光线会随意偏折。
In reflection, the angle of incidence (i) is always equal to the angle of reflection (r), both measured from the normal – an imaginary line perpendicular to the surface. The incident ray, reflected ray and normal all lie in the same plane.
反射时，入射角 (i) 永远等于反射角 (r)，两者都是从法线（垂直于表面的假想线）量起。入射线、反射线和法线在同一平面内。
Refraction happens when light passes from one medium to another, e.g. air to water. If light enters a denser medium, it bends towards the normal; if it enters a less dense medium, it bends away from the normal. This is why a straw in a glass of water looks bent at the surface.
当光从一种介质进入另一种介质（如从空气到水）时会发生折射。光进入光密介质时，会偏向法线；进入光疏介质时，会偏离法线。这就是为什么放在水杯里的吸管看起来在水面处弯折。
8. Sound Needs a Medium | 声音传播误区
Many students believe that sound can travel through empty space, often because they watch space movies where explosions make loud noises. They also think sound travels best in air compared to solids or liquids.
许多学生认为声音可以在真空中传播，常常因为他们看的太空电影里爆炸发出巨大响声。他们还认为声音在空气中比在固体或液体中传播得更好。
Sound is produced by vibrations and must have a medium (solid, liquid or gas) to travel. In a vacuum there are no particles, so sound cannot propagate. An electric bell in a vacuum jar will not be heard even if it is ringing.
声音由振动产生，必须靠介质（固体、液体或气体）传播。真空中没有粒子，因此声音无法传播。真空罩里的电铃即使在响也听不见铃声。
Sound actually travels faster in solids than in liquids, and faster in liquids than in gases, because particles are closer together and pass on the vibrations more quickly. Astronauts on the Moon must use radio to communicate since there is no atmosphere to carry sound.
实际上，声音在固体中传播最快，液体中其次，气体中最慢，因为固体粒子排列更紧密，振动传递更迅速。月球上的宇航员必须使用无线电通讯，因为月球没有大气层来传递声音。
9. State Changes and Temperature | 物态变化与温度误区
When heating ice, students often expect the temperature to keep rising smoothly, even while the ice is melting. They also confuse evaporation with boiling, and think the bubbles in boiling water are air escaping.
在加热冰时，学生通常以为温度会一直平稳上升，即使在冰熔化期间也一样。他们还混淆蒸发与沸腾，并认为沸水中的气泡是逸出的空气。
During a change of state – melting, boiling or freezing – the temperature stays constant even though heating continues. For pure ice at 0 °C, the temperature remains at 0 °C until all the ice has melted. The energy absorbed is used to break bonds between particles, not to raise temperature.
在物态变化过程中——熔化、沸腾或凝固——尽管继续加热，温度却保持不变。对于纯净的冰，在 0 °C 时直到全部熔化完毕，温度始终保持在 0 °C。吸收的能量用于破坏粒子间的键，而不是升高温度。
Evaporation happens at the surface of a liquid at any temperature, while boiling happens throughout the liquid at a fixed temperature (boiling point).
Published by TutorHao | Year 7 Physics Revision Series | aleveler.com
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