📚 Common Misconceptions in GCSE WJEC Science | GCSE WJEC科学常见误区
Many students lose marks in GCSE WJEC Science not because they don’t study, but because they carry deep-seated misconceptions about basic scientific ideas. These errors arise from everyday language, oversimplified teaching, or intuitive assumptions that conflict with the scientific model. This article uncovers the most common pitfalls across biology, chemistry, and physics and replaces them with the accurate knowledge required for the exam.
很多学生在GCSE WJEC科学考试中丢分，并不是因为没有复习，而是因为对一些基本科学概念抱有根深蒂固的误解。这些错误来源于日常用语、过度简化的教学或与科学模型相抵触的直觉假设。本文将揭示生物、化学和物理中最常见的误区，并用考试所需的准确知识加以纠正。
1. Forces and Motion: Constant Force Means Constant Speed? | 力与运动：恒力等于恒速度？
A widespread mistake is the belief that if a constant force is applied to an object, it will move at a constant speed. This comes from everyday experience, such as pushing a trolley at a steady pace. In reality, you are applying a force to overcome friction, so the net force is zero.
一个普遍的错误是认为若对物体施加恒定的力，它就会以恒定速度运动。这来自于日常经验，比如匀速推购物车。实际上，你施加力是为了克服摩擦力，因此合外力为零。
Newton’s second law states that a resultant (net) force causes acceleration, not steady speed. If a single constant force acts forward with no opposing forces, the object will continuously speed up (accelerate uniformly). It only moves at constant velocity when all forces are balanced—net force = 0.
牛顿第二定律指出，合（净）外力产生加速度，而不是恒定的速度。如果只有向前的恒定力且没有阻力，物体就会不断加速（匀加速）。只有当所有力平衡，即合外力为零时，物体才会保持恒定速度。
2. Cells: All Bacteria Are Harmful | 细胞：所有细菌都是有害的？
It is common for learners to label all bacteria as ‘germs’ and assume they always cause disease. This misconception overlooks the vast number of beneficial bacteria essential for life on Earth.
学生们常把所有细菌都标为“病菌”，并认为它们总会引起疾病。这个误解忽视了地球上大量对生命至关重要的有益细菌。
Beneficial bacteria live in our gut and help with digestion, while others are used to make yoghurt and cheese. Decomposer bacteria recycle nutrients in ecosystems, and nitrogen-fixing bacteria convert atmospheric nitrogen into forms plants can use. Only a small fraction of bacterial species are pathogenic.
有益细菌生活在我们的肠道内帮助消化，还有一些用于制作酸奶和奶酪。分解细菌在生态系统中循环养分，固氮细菌把大气中的氮转化为植物可用的形式。只有一小部分细菌物种是病原菌。
3. Energy: Energy Can Be ‘Used Up’ | 能量：能量会被“用完”？
The phrase ‘we have used up the energy’ is misleading. Many students think energy disappears after it has been used. The scientific principle of conservation of energy tells us energy cannot be created or destroyed, only transferred or transformed from one type to another.
“我们把能量用光了”这句话会误导。很多学生认为能量用完就消失了。能量守恒的科学原理告诉我们，能量既不能凭空产生，也不会凭空消失，只能从一种形式转移或转换为另一种形式。
For example, in a lamp, electrical energy is converted into light and heat. The total amount of energy remains the same, but some is dissipated as thermal energy to the surroundings, making it less useful for doing work. It is not ‘lost’, just spread out.
例如，在灯里，电能被转换成光和热。能量的总量不变，但一部分会以热能形式散失到周围环境中，使其不能再做有用的功。能量并没有“消失”，只是分散了。
4. Photosynthesis: Plants Get Their Food from the Soil | 光合作用：植物从土壤获取食物？
Many students think plants absorb food through their roots from the soil. This is incorrect. Plants are autotrophs; they manufacture their own food—glucose—via photosynthesis using carbon dioxide and water, powered by light energy absorbed by chlorophyll.
许多学生以为植物通过根从土壤吸收食物。这是错误的。植物是自养生物，它们通过光合作用自己制造食物——葡萄糖——使用二氧化碳和水，并依靠叶绿素吸收的光能驱动。
Roots absorb water and dissolved mineral ions, but these are not food; they are raw materials needed for plant growth and metabolism. The food plants produce is glucose, which is then used for respiration or stored as starch.
根吸收水分和溶解的矿物离子，但这些不是食物；它们是植物生长和代谢所需的原料。植物制造的食物是葡萄糖，随后用于呼吸作用或储存为淀粉。
5. Electricity: Current Is ‘Used Up’ in a Circuit | 电流在电路中被“消耗”？
A very common error is to think that electric current gets ‘used up’ as it flows through components, so that the current leaving a bulb is smaller than the current entering it. This does not match the scientific model of charge flow.
一个极常见的错误是认为电流在流经用电器时被“消耗”，因此流出灯泡的电流小于流入的电流。这与电荷流动的科学模型不符。
Current is the rate of flow of charge. In a series circuit, the current is the same everywhere. Charge is conserved; it is not consumed. Energy is transferred from the cell to the components (e.g. light and heat in a bulb), but the number of charges flowing per second remains constant.
电流是电荷的流动速率。在串联电路中，各处的电流都相等。电荷是守恒的，不会被消耗。能量从电池转移到元件（例如灯泡的光和热），但每秒通过的电荷数量保持不变。
6. Chemical Reactions: Mass Disappears When a Gas Is Produced | 化学反应：产生气体时质量会减少？
When a reaction produces a gas that escapes, students often conclude that mass is lost because the reading on a balance drops. This leads to the wrong idea that mass isn’t conserved in open systems.
当反应产生气体并使气体逸出时，学生常因天平读数下降而认为质量减少了。这导致错误观念，即在开放体系中质量不守恒。
The law of conservation of mass states that the total mass of products equals the total mass of reactants, provided no material enters or leaves the system. If the reaction is carried out in a sealed container, the mass stays the same. The apparent loss is simply because the gas has escaped the open reaction vessel.
质量守恒定律指出，只要没有物质进出体系，产物的总质量等于反应物的总质量。如果在密封容器中进行反应，质量不变。表面上的质量减少只是因为气体从敞口容器中逸出了。
7. Evolution: ‘Survival of the Fittest’ Means the Strongest | 进化：“适者生存”意味着最强壮？
The phrase ‘survival of the fittest’ leads many to picture the physically largest or most aggressive organism winning. In biology, however, ‘fitness’ refers to the ability of an organism to survive and reproduce in its specific environment.
“适者生存”这个说法让很多人联想到体型最大或最具攻击性的生物获胜。然而在生物学中，“适应性”指的是生物在其特定环境中生存和繁殖的能力。
An organism can be ‘fit’ because it has better camouflage, can resist a disease, can find food more efficiently, or has a faster reproductive cycle. Natural selection favours organisms with advantageous inherited characteristics—not necessarily the strongest.
一个生物“适应性强”可能是因为它有更好的伪装、能抵抗疾病、能更有效地寻找食物或有更快的繁殖周期。自然选择有利于具有有利遗传特征的生物——未必是最强壮的。
8. States of Matter: Particles Expand When Heated | 物态：粒子受热膨胀？
Students frequently draw diagrams showing particles (atoms or molecules) getting bigger when a substance is heated. This is incorrect. Heating does not change the physical size of the individual particles.
学生画图时经常把受热后的粒子（原子或分子）画得更大。这是错误的。加热并不会改变单个粒子的实际大小。
When a substance is heated, the particles gain kinetic energy and move or vibrate more vigorously. In solids and liquids, the increased movement results in the particles moving slightly further apart on average, which causes expansion. In gases, the particles move faster and occupy a larger volume, but the particles themselves stay the same size.
加热物质时，粒子获得动能，振动或运动更加剧烈。在固体和液体中，运动加剧导致粒子间的平均间距略微增大，从而引起膨胀。在气体中，粒子运动更快并占据更大体积，但粒子本身大小不变。
9. Heart and Circulation: Arteries Always Carry Oxygenated Blood | 心脏与循环：动脉总是携带充氧血？
‘Arteries carry oxygenated blood and veins carry deoxygenated blood’ is a rule many students learn—but it has an important exception. The definition of an artery is a blood vessel that carries blood away from the heart, regardless of its oxygen content.
“动脉输送充氧血，静脉输送缺氧血”是很多学生记住的规则——但有一个重要例外。动脉的定义是将血液带离心脏的血管，无论其含氧量如何。
The pulmonary artery carries deoxygenated blood from the heart to the lungs, and the pulmonary vein carries oxygenated blood from the lungs back to the heart. In the systemic circulation, arteries do carry oxygenated blood, but the pulmonary circuit is the key counter-example.
肺动脉将缺氧血从心脏运送至肺部，而肺静脉将充氧血从肺部运回心脏。在体循环中动脉确实输送充氧血，但肺循环是关键的例外。
10. Acids and Alkalis: A Strong Acid Is Always Concentrated | 酸与碱：强酸总是浓酸？
Everyday language often treats ‘strong’ and ‘concentrated’ as synonyms, but in chemistry they mean very different things. This confusion causes frequent errors when discussing pH and reactivity.
日常用语常把“强”和“浓”当作同义词，但在化学中它们含义截然不同。讨论pH和反应活性时常会因此出错。
The strength of an acid refers to the extent of ionisation in water. Strong acids like hydrochloric acid (HCl) fully dissociate into H⁺ and Cl⁻ ions, while weak acids such as ethanoic acid only partially dissociate. Concentration refers to how much acid is dissolved in a given volume of water. You can have a dilute strong acid and a concentrated weak acid.
酸的强度指其在水中的电离程度。强酸如盐酸(HCl)能完全解离成H⁺和Cl⁻离子，而弱酸如乙酸仅部分解离。浓度指单位体积水中溶解的酸的多少。可以有稀的强酸，也可以有浓的弱酸。
11. Respiration: Plants Only Respire at Night | 呼吸作用：植物只在夜晚呼吸？
Because plants produce oxygen during photosynthesis in the daytime, some students assume they only need to respire at night. This is a serious error: respiration is required for energy release at all times.
由于植物白天通过光合作用产生氧气，一些学生因而认为它们只在晚上才需要呼吸。这是个严重错误：呼吸作用为生命活动供能，需要全天进行。
Plant cells respire continuously, day and night, to release energy from glucose for active transport, growth, and other processes. During daylight, the rate of photosynthesis often exceeds the rate of respiration, so the net gas exchange shows oxygen release, but respiration never stops.
植物细胞日夜不停地进行呼吸作用，从葡萄糖中释放能量，用于主动运输、生长等过程。白天，光合作用速率通常超过呼吸速率，因此净气体交换表现为释放氧气，但呼吸从不停止。
12. Diffusion: Diffusion Requires a Membrane | 扩散：扩散需要膜？
After studying osmosis and active transport across cell membranes, students often wrongly link diffusion exclusively to membranes. Diffusion is a fundamental physical process that occurs in any fluid without the need for a barrier.
学完跨细胞膜的渗透作用和主动运输后，学生常错误地把扩散与膜绑定。扩散是一种基本的物理过程，在任何流体中都能发生，无需屏障。
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, resulting from random particle motion. It can happen in open air (e.g., perfume spreading in a room) or in liquids (e.g., a drop of ink dispersing in water). A membrane can influence which substances diffuse across it, but it is not a requirement for diffusion to take place.
扩散是粒子从高浓度区域向低浓度区域的净运动，源于粒子的随机运动。它可以在空气中发生（如香水的扩散），或在液体中发生（如墨水滴在水里散开）。膜可以影响哪些物质可以扩散通过，但膜并非扩散发生的必要条件。
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