📚 Year 7 OCR Science: Common Misconceptions and How to Correct Them | Year 7 OCR 科学：常见误区与纠正方法
Science is full of fascinating ideas, but it is easy to pick up misunderstandings that stick with us for years. In Year 7, you begin to develop a deeper view of the natural world, and that means unpacking some of the ‘obvious’ ideas you may have held before. This article identifies ten common misconceptions across biology, chemistry and physics, explains why they are wrong and shows you a clearer, more accurate way to think about each topic. By tackling these head‑on, you will build a stronger foundation for GCSE and beyond.
科学充满迷人的概念，但我们也容易形成一些误解，并在心里扎根多年。进入七年级，你会开始用更深入的眼光看待自然界，这就需要拆解一些过去认为“理所当然”的想法。本文梳理了生物、化学和物理中十个常见误区，解释它们为什么是错的，并指出更清晰、更准确的思考方式。直面这些误区，你将为 GCSE 及之后的学习打下更扎实的基础。
1. Plants Only Respire During the Day | 植物只在白天进行呼吸
Many students believe that plants breathe in carbon dioxide and breathe out oxygen during the day, but at night they do the opposite – or that they simply ‘stop respiring’ when the sun goes down. This wrong idea comes from mixing up photosynthesis and respiration. Photosynthesis does only happen in the light, so during the day a plant takes in CO₂ and releases O₂. Respiration, however, is happening all the time, day and night. In the dark, a plant cannot photosynthesise, so it only respires, taking in oxygen and giving out carbon dioxide. During the day, both processes run, but photosynthesis usually releases more oxygen than respiration uses, so the overall effect is oxygen release.
很多学生以为植物白天吸入二氧化碳、呼出氧气，晚上反过来——或者太阳下山后植物就“停止呼吸”。这个错误来源于把光合作用和呼吸作用混为一谈。光合作用的确只能在光下进行，因此白天植物吸收 CO₂、释放 O₂。然而呼吸作用全天进行，不论日夜。在黑暗中，植物不能进行光合作用，所以只进行呼吸，吸入氧气、呼出二氧化碳。白天两个过程同时发生，不过光合作用释放的氧气通常多于呼吸消耗的，因此总体表现为氧气的释放。
Correct understanding: Respiration is a continuous life process that releases energy from food in all living cells. It is not the same as breathing and does not stop at night. Photosynthesis, by contrast, is the way plants make their own food using light energy, and it only runs when light is available.
正确理解：呼吸是所有活细胞从食物中释放能量的持续生命过程，它和“喘气”不是一回事，也不会在夜晚停止。光合作用则是植物利用光能制造自己食物的方式，只在有光时进行。
2. A Force Keeps Things Moving | 力让物体保持运动
Everyday experience makes us say things like ‘you need to push a trolley to keep it moving’. From this, many students conclude that a constant force is necessary to maintain motion. In fact, if there were no friction or air resistance, an object would keep moving in a straight line at a steady speed without any force at all. A resultant force changes the motion – it can speed it up, slow it down or change its direction – but it is not needed to keep something moving. The trolley stops because friction acts against it; the push simply balances the friction, so the resultant force is zero and the trolley moves at a constant velocity.
日常经验让我们常说“推着购物车才能让它继续移动”。很多学生由此得出，维持运动需要一个恒定的力。实际上，假如没有摩擦或空气阻力，物体会沿着直线匀速运动下去，完全不需要力。合力的作用是改变运动——可以让物体加速、减速或改变方向——但并非维持运动的原因。购物车之所以停下来是因为摩擦在阻碍它；推它只是在平衡摩擦力，使合力为零，于是购物车能匀速前进。
- If all forces are balanced (resultant force = 0), an object stays at rest or moves at a constant speed in a straight line.
- 如果所有力平衡（合力 = 0），物体保持静止或沿直线匀速运动。
- An unbalanced force causes acceleration (speeding up, slowing down or changing direction).
- 不平衡的力导致加速（加速、减速或改变方向）。
3. Electricity Gets ‘Used Up’ in a Circuit | 电流在电路中被“用完”
A very persistent misconception is that electric current is consumed by bulbs or motors, so the current leaving a component is smaller than the current entering it. In a simple series circuit, the current is the same at every point. What gets transferred and used is energy, not electric charge. The battery provides energy to the charges, which then lose that energy in the bulb (making it light) or motor. The charges themselves continue around the circuit and return to the battery. Ammeters placed before and after a bulb will show identical readings.
一个非常顽固的误区是：灯泡或马达会“消耗”电流，因此进入元器件的电流比流出的要大。在简单的串联电路中，各点的电流是相同的。被传递和使用的是能量，而不是电荷。电池把能量给予电荷，电荷随后在灯泡（发光）或马达中失去这部分能量。电荷本身继续绕行电路，回到电池。把电流表接在灯泡前后，读数会完全相同。
Think of the current like a chain of people passing buckets of water. The buckets (charge) keep moving at the same rate everywhere, but the water (energy) is poured out at the point where work is done.
可以把电流想象成一队人传递水桶。水桶（电荷）在任何位置的移动速率都相同，但水（能量）在做功的地方被倒出。
4. Atoms Are Tiny Solid Balls That Cannot Be Divided | 原子是不可分割的实心小球
When atoms are first introduced, they are often drawn as small coloured spheres. This leads students to picture an atom as a hard, solid ball with no internal structure. In reality, an atom is mostly empty space. It has a tiny, dense nucleus containing protons and neutrons, surrounded by electrons that move in orbitals much further out. What appears ‘solid’ in everyday objects is the interaction of electric fields, not solid balls packed tightly together. Modern science shows that atoms can be split in nuclear reactions, revealing the sub‑atomic particles.
人们最初了解原子时，常把它们画成彩色小球。这使得学生把原子想象成坚硬的实心球体，没有内部结构。实际上，原子内部绝大部分是空的。它拥有一个极小、致密的原子核，由质子和中子组成，周围有电子在远得多的轨道上运动。日常物体之所以感觉“固体”，是电场相互作用的结果，而不是真的有许多实心小球紧紧挤在一起。现代科学表明，原子可以在核反应中被分裂，暴露出亚原子粒子。
| Sub‑atomic particle | Relative charge | Location |
| Proton | +1 | Nucleus |
| Neutron | 0 | Nucleus |
| Electron | -1 | Orbitals around nucleus |
亚原子粒子：质子（带+1电荷，位于原子核）、中子（不带电，位于原子核）、电子（带-1电荷，绕核运动）。
5. Mass Disappears or Appears in Chemical Reactions | 化学反应中质量会消失或创造出来
Observing a candle burn, rust form or a log turn to ash, students often think that matter is lost because the remaining solid weighs less. Others think gas bubbles appear ‘from nowhere’. The principle of conservation of mass states that in a chemical reaction, no atoms are created or destroyed; they are only rearranged. The total mass of reactants equals the total mass of products. In an open system, gases may escape into the air, making it seem that mass has vanished. If you capture all products (including gases), the mass stays the same.
看到蜡烛燃烧、铁生锈或木头变成灰烬，学生常常认为物质消失了，因为剩下的固体变轻了。还有人觉得气泡是凭空出现的。质量守恒定律指出，在化学反应中，原子不会被创造也不会被消灭，只是重新排列。反应物的总质量等于生成物的总质量。在开放体系中，气体会逃逸到空气中，看起来好像质量减少了。如果将所有产物（包括气体）都收集起来，总质量保持不变。
For example, when magnesium burns in air: 2Mg + O₂ → 2MgO. The mass of the magnesium oxide produced is the combined mass of magnesium and oxygen that reacted. The solid alone might seem heavier because oxygen from the air has joined it.
例如，镁在空气中燃烧：2Mg + O₂ → 2MgO。生成的氧化镁的质量等于参与反应的镁和氧气的质量之和。单看固体似乎变重了，那是因为空气中的氧气加入了反应。
6. All Microbes Are Harmful Germs | 所有微生物都是有害的病菌
Words like ‘germ’ and ‘bacteria’ immediately make many Year 7 students think of disease. In truth, most bacteria are harmless, and many are essential. Bacteria in our gut help digest food and produce vitamins. Microorganisms are used to make bread (yeast), yoghurt (bacteria), and to break down waste in compost heaps. Only a small fraction of microbes cause illness. Some fungi produce antibiotics, and soil bacteria cycle nutrients that plants need.
一听到“病菌”、“细菌”这些词，很多七年级学生立刻联想到疾病。事实上，大多数细菌是无害的，还有很多是必不可少的。肠道中的细菌帮助我们消化食物并产生维生素。微生物可以用来制作面包（酵母）、酸奶（细菌），还可以分解堆肥中的废物。只有一小部分微生物会导致疾病。一些真菌能产生抗生素，土壤中的细菌则循环植物所需的养分。
Useful examples: Lactobacillus turns milk into yoghurt; Saccharomyces cerevisiae (yeast) raises bread; nitrogen‑fixing bacteria in root nodules help legumes grow.
有用的例子：乳酸菌把牛奶变成酸奶；酿酒酵母（酵母菌）让面包膨发；根瘤中的固氮菌帮助豆科植物生长。
7. Weight and Mass Are the Same Thing | 重量和质量是一回事
In everyday language we often say ‘how much does it weigh?’ when we really mean ‘what is its mass?’. Mass is the amount of matter in an object and is measured in kilograms (kg). It does not change wherever you are in the universe. Weight is the force of gravity acting on that mass, measured in newtons (N). Your mass is the same on Earth and on the Moon, but your weight is about six times less on the Moon because the Moon’s gravity is weaker. This distinction becomes crucial when studying forces and motion.
在日常语言中，我们常问“它有多重？”，其实指的是“它的质量是多少？”。质量是物体所含物质的量，单位是千克（kg），无论在宇宙何处都不变。重量是作用在该质量上的重力，单位是牛顿（N）。你在地球和月球上的质量相同，但月球上的重量大约是地球上的六分之一，因为月球的引力更弱。在学习力和运动时，这个区别非常关键。
Weight (N) = Mass (kg) × Gravitational field strength (N/kg)
重量 (N) = 质量 (kg) × 重力场强度 (N/kg)
On Earth, g ≈ 10 N/kg, so a 5 kg object has a weight of 50 N. On the Moon, g ≈ 1.6 N/kg, so the same object weighs only about 8 N.
地球上 g ≈ 10 N/kg，因此 5 kg 的物体重约 50 N。月球上 g ≈ 1.6 N/kg，同一物体仅重约 8 N。
8. Shadows Are the Colour of the Object | 影子是物体本身的颜色
Younger children sometimes draw a green shadow for a green leaf, or imagine that a red ball casts a red shadow. A shadow is simply a region where light cannot reach because it is blocked by an opaque object. Shadows look dark (usually black or grey) because there is less light compared to the illuminated area around them. If the light source has a colour, the lit area may appear tinted, but the shadow itself remains dark. A coloured filter can change the colour of light, but a shadow is the absence of that light, not a projection of the object’s colour.
年幼的孩子有时会把绿叶的影子画成绿色，或想象红色的球投下红色的影子。影子其实只是一个光线无法到达的区域，因为它被不透明的物体挡住了。影子看起来是暗的（通常是黑色或灰色），是因为比起周围被照亮的区域，那里的光比较少。如果光源有颜色，被照亮的地方可能带上色彩，但影子本身仍然是暗的。彩色滤光片能改变光的颜色，但影子是光的缺失，不是物体颜色的投影。
Try it: Use a torch with different colour filters to cast a shadow. The wall behind the object changes colour, but the shadow remains dark.
试试看：用手电筒加上不同颜色的滤光片照出影子。物体背后的墙壁会变色，但影子始终是暗的。
9. Dissolving Means the Solid Disappears | 溶解意味着固体消失
When salt or sugar dissolves in water, it seems to ‘vanish’. This gives rise to the idea that matter is destroyed in dissolving. In reality, the solute particles separate and spread out evenly among the water particles, but they are still there. You can taste the sugar even if you cannot see it, and you can recover the solute by evaporating the water. Dissolving is a physical change, not a chemical one, because no new substances are formed. The total mass of solute plus solvent stays constant.
盐或糖在水中溶解时，看起来“不见了”。这让人以为物质在溶解过程中被消灭了。事实上，溶质粒子只是分散开来，均匀地分布在水分子之间，但它们仍然存在。即使看不见糖，你也能尝到它的甜味；通过蒸发掉水，就能重新得到溶质。溶解是一种物理变化，不是化学变化，因为没有生成新物质。溶质加溶剂的总质量保持不变。
Key evidence: If you weigh the beaker, water and salt before and after dissolving (without spilling), the total mass is unchanged.
关键证据：如果称量烧杯、水和盐溶解前后的总质量（没有洒出），总质量不变。
10. All Acids Are Dangerous and Eat Through Everything | 所有酸都是危险的，能腐蚀一切
Television and films often show acids as green, fuming liquids that dissolve metal and flesh instantly. This creates an exaggerated fear. Many acids we encounter daily are weak and safe to handle. Citric acid in lemons, ethanoic acid in vinegar, and carbonic acid in fizzy drinks are all acids. Strong laboratory acids (hydrochloric, sulfuric, nitric) are corrosive, but they can be used safely with proper precautions. What makes an acid an acid is the presence of hydrogen ions (H⁺); it does not automatically mean it is deadly.
电视和电影经常把酸描绘成冒着绿烟的液体，能瞬间溶解金属和肉体。这造成了夸大的恐惧。我们日常接触的许多酸是弱酸，能安全处理。柠檬中的柠檬酸、醋中的乙酸、气泡饮料中的碳酸都是酸。实验室里的强酸（盐酸、硫酸、硝酸）具有腐蚀性，但只要采取正确的防护措施就能安全使用。使酸成为酸的是氢离子（H⁺）的存在，并不自动意味着它是致命的。
Safe acids in the kitchen: lemon juice (pH ~2-3), vinegar (pH ~2.4), fizzy cola (pH ~2.5). Even your stomach contains hydrochloric acid to help digest food.
厨房中安全的酸：柠檬汁（pH 约 2-3）、醋（pH 约 2.4）、可乐（pH 约 2.5）。就连你的胃里也含有帮助消化食物的盐酸。
11. Food Chains Start with the Sun | 食物链的起点是太阳
A frequent error in drawing food chains is to put the Sun at the beginning as the first ‘organism’. Food chains represent feeding relationships between living things. The Sun is not a living organism; it provides the energy that producers (plants and algae) use to make food. A correct food chain always starts with a producer, such as grass or a phytoplankton. The arrows show the direction of energy transfer, from eaten to eater. Example: grass → rabbit → fox. The Sun can be mentioned as the energy source, but it is not part of the chain itself.
绘制食物链时常见的错误是把太阳作为第一个“生物”放在开头。食物链表示的是生物之间的摄食关系。太阳不是生物；它为生产者（植物和藻类）制造食物提供能量。正确的食物链总是从生产者开始，比如草或浮游植物。箭头表示能量传递的方向，从被吃者指向吃者。例如：草 → 兔子 → 狐狸。太阳可以作为能量来源提及，但它不属于食物链本身。
Tip: When asked to ‘draw a food chain’, do not include the Sun or arrows pointing from the Sun. Start with a green plant.
提示：要求“画一条食物链”时，不要把太阳放进去，也不要画出从太阳出发的箭头。从一个绿色植物开始。
12. Sound Travels Through Empty Space | 声音能在真空中传播
Science‑fiction films often show explosions in space with loud bangs, leading many students to believe sound can travel through a vacuum. Sound is a mechanical wave that needs a medium (solid, liquid or gas) to vibrate particles. In the near‑vacuum of space, there are too few particles to carry the vibrations, so sound cannot travel. That is why astronauts use radio communication, which is electromagnetic and does not need a medium. Light, on the other hand, can travel through empty space.
科幻电影经常展示太空中的爆炸伴随巨大响声，这让许多学生以为声音能在真空中传播。声音是一种机械波，需要介质（固体、液体或气体）让粒子振动。在近乎真空的太空里，粒子太少，无法传递振动，所以声音不能传播。这就是为什么宇航员使用无线电通信——无线电是电磁波，不需要介质。而光却能在真空中传播。
Classroom demonstration: Place a ringing bell inside a vacuum jar and pump out the air. The sound fades away even though you can still see the hammer moving.
课堂演示：把响铃放进真空罩里，抽出空气。随着空气被抽走，铃声逐渐消失，但你仍然能看见铃锤在动。
Published by TutorHao | Science Revision Series | aleveler.com
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