📚 Year 7 WJEC Chemistry: Common Misconceptions and How to Correct Them | Year 7 WJEC 化学：常见误区与纠正方法
In Year 7 WJEC Chemistry, students encounter foundational ideas that shape their understanding of the material world. However, some concepts are often misunderstood, leading to persistent misconceptions. This article highlights the most common errors and provides clear corrections to help learners build a solid chemical knowledge base.
在 Year 7 WJEC 化学中，学生接触到塑造物质世界理解的基础概念。然而，一些概念常常被误解，导致持久的误区。本文指出最常见的错误并提供清晰的纠正，帮助学生建立坚实的化学知识基础。
1. Particles in Solids Are Motionless | 固体中的粒子是静止不动的
Many learners imagine solid particles as completely frozen in place, like statues. They think there is no movement at all because a solid keeps its shape and cannot be poured.
许多学生认为固体粒子像雕塑一样完全固定，没有任何运动。因为固体能保持形状且不能倾倒，他们就以为粒子不动。
In reality, particles in a solid do not move past each other, but they vibrate constantly around fixed positions. This vibration is evidence of their kinetic energy and explains why solids expand slightly when heated.
实际上，固体中的粒子不能彼此移动，但它们在固定位置不停地振动。这种振动是它们动能的证据，也解释了为什么固体受热会略微膨胀。
This tiny movement can be linked to temperature: the hotter the solid, the more vigorously its particles vibrate. Without motion, solids could not absorb heat energy and melt.
这种微小的运动与温度有关：固体越热，其粒子振动越剧烈。如果没有运动，固体无法吸收热量并熔化。
2. Bubbles in Boiling Water Are Air | 沸水中的气泡是空气
When water boils, large bubbles rise vigorously to the surface. Many Year 7 pupils believe these bubbles are made of air trapped in the liquid, escaping as the water gets hot.
当水沸腾时，大气泡剧烈地上升到表面。许多 Year 7 学生认为这些气泡是由被困在液体中的空气构成的，随着水温升高而逸出。
The bubbles are actually filled with water vapour – water in its gaseous state. Inside each bubble, liquid water has changed state into an invisible gas called steam. It is a change of state, not trapped air escaping.
这些气泡实际上充满了水蒸气——气态的水。在每一个气泡内部，液态水变成了看不见的水蒸气。这是状态变化，而不是被困的空气逸出。
You can prove this by observing that bubbles only form at the boiling point, whereas dissolved air would bubble out much sooner at lower temperatures.
你可以通过观察证明这一点：气泡只在沸点时大量形成，而溶解的空气在较低温度下就会提早逸出。
3. Dissolving Means the Substance Disappears | 溶解意味着物质消失了
When salt or sugar dissolves in water, students often say the substance has 'vanished' because the resulting liquid looks perfectly clear.
当盐或糖溶于水时，学生经常说物质“消失”了，因为得到的液体看起来完全透明。
The substance is still present; its particles have been pulled apart and spread evenly among water molecules to form a solution. The mass of the solute is conserved, and the solution is heavier than pure water.
该物质依然存在；它的粒子被拉开，均匀地分散在水分子之间，形成溶液。溶质的质量得以保存，溶液比纯水更重。
If you evaporate the water gently, the dissolved solid will be left behind, proving it did not disappear. Tasting the salt water also confirms the salt is still there, even though you cannot see it.
如果你轻轻蒸发水分，溶解的固体会残留下来，证明它并未消失。尝一口盐水也能证实盐依然存在，尽管你看不到它。
4. Mass Is Lost During Chemical Reactions | 化学反应中质量会消失
Pupils may think that mass decreases when a substance burns, because the remaining ash is lighter than the original material. Some also think gases have no mass and simply float away without affecting the total.
学生可能认为物质燃烧时质量会减少，因为剩下的灰烬比原材料轻。有些人还认为气体没有质量，飘走后不影响总质量。
In a closed system, the total mass before and after a reaction stays exactly the same. When a log burns, the gases produced (carbon dioxide and water vapour) escape into the room, so the solid leftovers weigh less. If you could trap all the gases, the total mass would remain unchanged.
在封闭系统中，反应前后的总质量完全相同。当木头燃烧时，产生的气体（二氧化碳和水蒸气）逸散到空气中，因此固体残余物重量减轻。如果你能收集所有气体，总质量将保持不变。
For example, magnesium burning in air gains mass because it combines with oxygen from the air to form magnesium oxide. Atoms are rearranged, never destroyed or created – this is the law of conservation of mass.
例如，镁在空气中燃烧质量增加，因为它与空气中的氧气结合形成氧化镁。原子重新排列，永远不会被消灭或创造——这就是质量守恒定律。
5. All Acids Are Dangerous, All Bases Are Safe | 所有酸都是危险的，所有碱都是安全的
Many students associate acid with burns and danger, while viewing bases like soap or baking soda as completely harmless. They often label all acids as 'strong' and all alkalis as 'weak'.
许多学生将酸与烧伤和危险联系在一起，而认为像肥皂或小苏打之类的碱完全无害。他们常把所有酸标为“强”，所有碱标为“弱”。
The hazard depends on concentration, not just identity. Both concentrated acids and concentrated alkalis can be corrosive and cause skin burns. A strong base such as sodium hydroxide can be just as dangerous as hydrochloric acid.
危害取决于浓度，而不仅仅是物质的性质。浓酸和浓碱都可能具有腐蚀性并导致皮肤灼伤。强碱如氢氧化钠可以和盐酸一样危险。
Weak acids like citric acid in lemon juice are safe to consume, while common kitchen bases include ammonia-based cleaners that are hazardous. The pH scale tells us acidity or alkalinity, but does not directly indicate safety.
柠檬汁中的柠檬酸等弱酸可以安全食用，而含氨清洁剂等常见家用碱却是危险的。pH 值标度告诉我们酸性或碱性，但不能直接表明安全性。
6. Natural Means Pure | 天然就是纯净
Students often describe milk, orange juice, or sea water as 'pure' substances because they come from nature and look uniform. They confuse the everyday meaning of pure (clean, unprocessed) with the scientific meaning.
学生经常将牛奶、橙汁或海水描述为“纯”物质，因为它们来自自然界且看起来均匀。他们混淆了日常用语（干净、未加工）和科学含义中的“纯”。
In chemistry, a pure substance consists of only one type of particle – either a single element like gold or a single compound like distilled water (H₂O). Mixtures contain two or more different substances not chemically combined.
在化学中，纯物质只包含一种粒子——单一元素如黄金，或单一化合物如蒸馏水（H₂O）。混合物含有两种或更多未化学结合的不同物质。
Milk is a mixture of water, fats, proteins, and sugars. Seawater contains dissolved salts and minerals. These natural liquids are mixtures, not chemically pure.
牛奶是水、脂肪、蛋白质和糖的混合物。海水含有溶解的盐和矿物质。这些天然液体是混合物，不是化学纯的。
7. Evaporation Only Happens at the Boiling Point | 蒸发只在沸点发生
Some pupils believe that a puddle of water can only turn into vapour when it reaches 100 °C. They think evaporation is the same as boiling, just a bit slower.
一些学生认为水坑只有在达到 100 °C 时才能变成水蒸气。他们以为蒸发和沸腾是一回事，只是慢一点。
Evaporation occurs at any temperature from the surface of a liquid. Wet clothes dry on a line even on a cold, windy day because high-energy particles near the surface escape into the air.
蒸发在任何温度下都会从液体表面发生。湿衣服即使在寒冷的刮风天也会晾干，因为表面附近高能量的粒子逸散到空气中。
Boiling is different: it happens rapidly throughout the entire liquid at a specific temperature – the boiling point – forming bubbles of vapour everywhere. Evaporation is a slower, surface-only process.
沸腾则不同：它在特定温度（沸点）下整个液体内部快速发生，到处形成蒸气泡。蒸发是较慢的、仅发生在表面的过程。
8. Gases Have No Mass | 气体没有质量
Because gases are often invisible and seem to 'disappear' when a bottle is opened, many children think gases weigh nothing at all.
由于气体通常是看不见的，并且打开瓶子似乎就“消失”了，许多孩子认为气体完全没有重量。
All matter, including gases, has mass. A deflated balloon weighs less than the same balloon after it has been inflated, because the air inside adds a measurable amount of mass.
所有物质，包括气体，都有质量。瘪的气球比同一个气球充气后轻，因为内部的空气增加了可测量的质量。
Gases such as oxygen (O₂) and carbon dioxide (CO₂) are made of particles. A balloon filled with carbon dioxide is noticeably heavier than one filled with air, showing that different gases have different masses.
氧气（O₂）和二氧化碳（CO₂）等气体由粒子构成。充满二氧化碳的气球明显比充满空气的气球重，这表明不同气体具有不同的质量。
9. Filtration Can Separate Dissolved Solids | 过滤可以分离溶解的固体
A common mistake is to suggest using filter paper and a funnel to remove salt from salty water. Students imagine the salt getting 'caught' like sand.
一个常见错误是建议使用滤纸和漏斗从盐水中去除盐。学生想象盐会像沙子一样被“截住”。
Filtration only separates an insoluble solid from a liquid. The tiny dissolved salt particles pass straight through the pores of the filter paper, so the filtered water still tastes salty.
过滤只能分离不溶性固体与液体。微小的溶解盐粒子直接穿过滤纸的孔隙，因此过滤后的水尝起来仍是咸
Published by TutorHao | Year 7 Chemistry Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图