📚 GCSE WJEC Chemistry Practical Guide | GCSE WJEC 化学实验操作指南
Welcome to the comprehensive practical guide for GCSE WJEC Chemistry. Mastering practical skills is essential not only for your exams but for understanding how chemistry works in the real world. This article covers key techniques, apparatus, and safety measures you will encounter in your practical assessments.
欢迎阅读 GCSE WJEC 化学综合实验操作指南。掌握实验技能不仅对考试至关重要，也有助于理解化学如何在现实世界中运作。本文涵盖了你在实验评估中会遇到的关键技术、仪器和安全措施。
1. Safety in the Laboratory | 实验室安全
Always wear safety goggles and a lab coat to protect your eyes and skin from chemical splashes. Long hair must be tied back and any dangling jewellery removed before starting work.
务必佩戴护目镜和实验服，以保护眼睛和皮肤免受化学飞溅的伤害。开始实验前，长发必须束起，并取下所有悬挂的首饰。
Never eat, drink or taste chemicals in the lab. Wash your hands thoroughly after handling any reagent, and ensure that all reagent bottles are clearly labelled.
在实验室不得饮食或品尝化学品。接触任何试剂后要彻底洗手，并确保所有试剂瓶都有清晰的标签。
When heating substances, always point the open end of a test tube away from yourself and others. Use a blue Bunsen flame for quick heating and a yellow safety flame when the burner is not in immediate use.
加热物质时，试管开口端务必远离自己和他人。快速加热时使用蓝色本生灯火焰，不立即使用时将火焰调至黄色安全焰。
In case of acid spills on the skin, wash the affected area with plenty of water. Report any accident, even a minor one, to your teacher immediately.
如果皮肤溅到酸液，立即用大量清水冲洗。任何意外，即使不严重，都必须立即报告老师。
2. Basic Laboratory Equipment | 基本实验室设备
Beakers are used for mixing, heating and holding liquids. They are not calibrated for accurate volume measurement and should only be used when approximate volumes are acceptable.
烧杯用于混合、加热和盛放液体。它们没有精确体积刻度，只适合在允许近似体积的场合使用。
Conical flasks are ideal for swirling solutions without spillage, making them a good choice for titrations. A volumetric flask is designed to prepare a very specific volume of solution with high accuracy.
锥形瓶适合晃动溶液而不溅出，非常适合滴定实验。容量瓶则用于配制精确体积的溶液，准确度很高。
Measuring cylinders provide reasonable accuracy for measuring liquid volumes. For precise work, a pipette or a burette should be used, as they can deliver volumes to the nearest drop or 0.05 cm³.
量筒在测量液体体积时能提供合理的准确度。需要高精度时，应使用移液管或滴定管，它们可以精确到一滴或 0.05 cm³。
A watch glass holds solid samples, while an evaporating dish is used to evaporate liquids and obtain solid residues. Crucibles are used with strong heating, especially for flame tests.
表面皿用于盛放固体样品，蒸发皿用于蒸发液体并获得固体残留物。坩埚用于强热，特别是在火焰测试时使用。
3. Measuring Mass and Volume | 测量质量与体积
Use a digital top-pan balance to measure mass, recording values to two decimal places. Always place a weighing boat or paper on the pan and reset the balance to zero before adding the substance.
使用数字顶盘天平测量质量，记录到小数点后两位。务必先在秤盘上放置称量舟或称量纸，归零后再添加物质。
When using a measuring cylinder, read the bottom of the meniscus at eye level to avoid parallax errors. For volumes of 25.0 cm³ or smaller, a pipette delivers a fixed volume more precisely.
使用量筒时，平视读取液面弯月形底部，以避免视差。对于 25.0 cm³ 或更小的体积，移液管能更精确地移取固定体积的液体。
A burette is essential for titration. It is graduated to 0.1 cm³, and readings should be recorded to two decimal places, with the second decimal being either 0 or 5 (e.g. 23.45 cm³) for consistency.
滴定管是滴定实验的必备仪器。其刻度为 0.1 cm³，读数应记录到小数点后两位，为使读数一致，第二位小数为 0 或 5（例如 23.45 cm³）。
To prepare a solution of known concentration, dissolve a weighed mass of solute in a small volume of water in a beaker, transfer it completely to a volumetric flask, and add water to the graduation mark.
配制已知浓度的溶液时，先在烧杯中用少量水溶解称量好的溶质，再全部转移至容量瓶中，加水至刻度线。
4. Heating Techniques and the Bunsen Burner | 加热技术与本生灯
The Bunsen burner has two main flame types: the yellow safety flame, visible and relatively cool, and the roaring blue flame, which is hot and almost invisible. Always light the burner with a slightly open air hole to produce a gentle blue flame.
本生灯有两种主要火焰：黄色安全焰可见且温度较低，而蓝色启燃焰温度高且几乎看不见。点火时应将气孔稍微打开，产生柔和的蓝色火焰。
Direct heating of a liquid in a test tube should be done gently, moving the tube in and out of the flame on a slant, not at the bottom centre, to avoid bumping. Use a water bath for flammable liquids.
直接加热试管中的液体时应温和进行，倾斜试管并在火焰中进出移动，不可固定加热底部中央，以防暴沸。加热易燃液体必须使用水浴。
A crucible and lid are used for strong heating of solids, such as in flame tests or thermal decomposition. Hold the crucible with tongs, and always allow it to cool on a heatproof mat.
坩埚与盖用于强热固体，例如火焰测试或热分解。用坩埚钳夹取坩埚，之后务必放在隔热垫上冷却。
When heating a beaker of water, place a tripod and gauze over the Bunsen burner. The gauze spreads the flame and supports the beaker evenly. Never heat a closed container.
加热烧杯中的水时，在本生灯上方放置三脚架和网垫。网垫分散火焰并能均匀支撑烧杯。严禁加热密闭容器。
5. Preparing and Collecting Gases | 气体制备与收集
To prepare oxygen, decomposing hydrogen peroxide using manganese(IV) oxide as a catalyst is the most common method. The reaction is quick and produces a colourless gas.
最常用的制氧方法是过氧化氢在二氧化锰催化下分解。反应快速，产生无色气体。
2H₂O₂(aq) → 2H₂O(l) + O₂(g)
Carbon dioxide is prepared by reacting a carbonate with a dilute acid, for instance calcium carbonate with hydrochloric acid. This gas turns limewater milky.
二氧化碳可通过碳酸盐与稀酸反应制备，例如碳酸钙与盐酸反应。该气体能使石灰水变浑浊。
CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)
Hydrogen can be generated by adding a reactive metal such as zinc to dilute sulfuric or hydrochloric acid. It burns with a squeaky pop when tested with a lit splint.
氢气可通过将锌等活泼金属加入稀硫酸或盐酸中制得。用点燃的木条检验时，氢气燃烧会发出爆鸣声。
Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)
Gases are collected by downward delivery (for gases denser than air, e.g. CO₂, Cl₂), upward delivery (for gases less dense than air, e.g. H₂, NH₃), or over water (for gases that are insoluble or only slightly soluble, e.g. O₂, H₂). Always check that the gas does not react with water before using the water method.
收集气体可采用向下排空气法（适用于比空气重的气体，如 CO₂、Cl₂）、向上排空气法（适用于比空气轻的气体，如 H₂、NH₃）或排水集气法（适用于难溶或微溶于水的气体，如 O₂、H₂）。使用排水法前务必确认气体不与水反应。
6. Filtration, Evaporation and Crystallisation | 过滤、蒸发与结晶
Filtration separates an insoluble solid from a liquid. Fold filter paper into a cone, place it in a funnel, and pour the mixture carefully so the filtrate passes through while the residue stays on the paper.
过滤用于分离不溶性固体和液体。将滤纸折叠成锥形放入漏斗中，小心倒入混合物，滤液通过滤纸而残渣留在纸面上。
Evaporation is used to recover a soluble solid from a solution, such as obtaining sodium chloride from salt water. Pour the solution into an evaporating dish and heat gently over a water bath until crystals start to form, then stop heating and allow the rest of the water to evaporate at room temperature.
蒸发用于从溶液中回收可溶性固体，例如从盐水中获取氯化钠。将溶液倒入蒸发皿，在水浴上缓缓加热，直至晶体开始析出，停止加热，让剩余水分在室温下蒸干。
Crystallisation yields pure, well-shaped crystals. For example, to prepare copper(II) sulfate crystals, heat the solution to make it saturated, allow it to cool slowly, and collect the crystals by filtration. Dry them between sheets of filter paper.
结晶法可获得纯净、形状完好的晶体。例如制备硫酸铜晶体时，加热溶液使其饱和，再缓慢冷却，过滤收集晶体，最后在滤纸间吸干。
Never evaporate to dryness if you want crystals because impurities may also remain solid. Slow cooling produces larger crystals while rapid cooling gives small, irregular ones.
若想获得晶体，切勿蒸干，因为杂质也可能同时残留在固体中。缓慢冷却会生成较大晶体，快速冷却则获得细小而不规则的晶体。
7. Acid-Base Titration | 酸碱滴定
Titration is a quantitative technique to determine the concentration of an unknown solution by reacting it with a solution of known concentration. Rinse the burette with the titrant, fill it, and record the initial volume to two decimal places.
滴定是一种定量技术，通过将未知溶液与已知浓度的溶液反应来测定其浓度。先用滴定剂润洗滴定管，装入溶液后记录初始体积，读数至小数点后两位。
Use a pipette and pipette filler to transfer exactly 25.0 cm³ of the analyte into a clean conical flask. Add 2–3 drops of a suitable indicator, such as phenolphthalein for a strong acid–strong base titration, which changes from colourless to pink at the endpoint.
用移液管和洗耳球准确移取 25.0 cm³ 待测液于干净的锥形瓶中，加入 2–3 滴合适的指示剂。例如强酸强碱滴定时使用酚酞，终点时由无色变为粉红色。
Place the conical flask on a white tile under the burette tip. Run the titrant in while swirling the flask constantly. When the indicator begins to change colour, add the titrant dropwise until a permanent colour change is achieved.
将锥形瓶放在滴定管下方白瓷板上。一边旋转锥形瓶一边加入滴定剂。当指示剂开始变色时，应逐滴加入，直至颜色产生持久变化。
Record the final burette reading. Repeat the titration until you obtain concordant results (within 0.10 cm³ of each other), then calculate the average volume of titrant used.
记录滴定管最终读数。重复滴定，直到获得一致性结果（彼此相差在 0.10 cm³ 以内），然后计算所用滴定剂的平均体积。
| Common indicator | Colour in acid | Colour in alkali | 常用指示剂 | 酸性中颜色 | 碱性中颜色 |
|---|---|---|---|---|---|
| Phenolphthalein | Colourless | Pink | 酚酞 | 无色 | 粉红 |
| Methyl orange | Red | Yellow | 甲基橙 | 红 | 黄 |
8. Chromatography | 色谱法
Paper chromatography separates mixtures of soluble substances, such as inks or food colourings. Draw a pencil baseline about 1.5 cm from the bottom edge of the filter paper; never use ink because it will also separate.
纸色谱法用于分离可溶物质的混合物，如墨水或食用色素。在滤纸底端约 1.5 cm 处用铅笔画一条基线，绝不可使用墨水，因为它也会被分离。
Place a small spot of the mixture on the baseline using a fine capillary tube. Allow the spot to dry, then apply a second spot on top to increase concentration.
用细毛细管在基线上点一小点混合物，待其干燥后再在原处点一次，以增加浓度。
Suspend the paper in a beaker with a small amount of solvent (e.g. water or ethanol) so that the baseline is above the solvent level. As the solvent rises, the different components move up the paper at different rates.
将滤纸悬挂在盛有少量溶剂（如水或乙醇）的烧杯中，基线应位于溶剂液面上方。随着溶剂上升，不同组分会以不同速率上移。
When the solvent front has travelled about two-thirds of the way up, remove the paper and mark the solvent front immediately with pencil. Calculate the Rf value for each component: Rf = distance moved by solute spot ÷ distance moved by solvent front.
当溶剂前沿上升到约三分之二高度时，取出滤纸，立即用铅笔标出溶剂前沿。计算各组分的 Rf 值：Rf = 溶质点移动距离 ÷ 溶剂前沿移动距离。
Since Rf values are characteristic of a substance under fixed conditions, they can be used to identify unknown components. Make sure to use the same paper and solvent for reliable comparison.
由于在固定条件下 Rf 值是物质的特征值，可用于鉴别未知组分。为进行可靠的比较，必须使用相同的滤纸和溶剂。
9. Testing for Ions and Gases | 离子与气体的检验
For gases, simple chemical tests give quick confirmation. Insert a glowing splint into a test tube of gas; if it relights, oxygen is present. A lit splint placed into the mouth of a test tube produces a squeaky pop with hydrogen.
简单的化学检验可快速确认气体。将带火星的木条伸入装有气体的试管，若重新燃烧，说明存在氧气。用点燃的木条在试管口检验，若发出爆鸣声则为氢气。
Bubble the gas through limewater; carbon dioxide turns it milky. Damp blue litmus paper turns red then bleaches white in the presence of chlorine gas. Ammonia turns damp red litmus paper blue.
将气体通入石灰水，出现白色浑浊证明是二氧化碳。湿润的蓝色石蕊试纸遇到氯气先变红后褪色变白。氨气能使湿润的红色石蕊试纸变蓝。
For anions, sulfate ions are detected by adding dilute hydrochloric acid and then barium chloride solution; a white precipitate of barium sulfate forms. Carbonate ions fizz when acid is added; the gas evolved can be tested with limewater.
检验阴离子时，先加稀盐酸再加氯化钡溶液可检测硫酸根离子，生成白色硫酸钡沉淀。加入酸时产生气泡说明存在碳酸根离子，逸出的气体可用石灰水检验。
Halide ions form coloured precipitates with silver nitrate solution followed by dilute nitric acid: chloride gives white silver chloride, bromide yields cream silver bromide, and iodide forms yellow silver iodide.
卤素离子与硝酸银溶液和稀硝酸反应生成有色沉淀：氯离子生成白色氯化银，溴离子生成淡黄色溴化银，碘离子生成黄色碘化银。
| Test | Observation | 检验项目 | 现象 |
|---|---|---|---|
| Flame test: Li⁺ | Crimson red | 焰色反应：Li⁺ | 深红色 |
| Flame test: Na⁺ | Yellow | 焰色反应：Na⁺ | 黄色 |
| Flame test: K⁺ | Lilac | 焰色反应：K⁺ | 淡紫色 |
| Flame test: Ca²⁺ | Orange-red | 焰色反应：Ca²⁺ | 橙红色 |
| Flame test: Cu²⁺ | Green-blue | 焰色反应：Cu²⁺ | 蓝绿色 |
10. Flame Tests and pH Measurement | 火焰测试与pH测量
Flame tests help identify certain metal cations by the characteristic colour they impart to a Bunsen flame. Clean a nichrome wire loop in concentrated hydrochloric acid, dip it in the sample powder, and hold the loop in the edge of a roaring blue flame.
火焰测试通过特定金属阳离子在本生灯火焰中产生的特征颜色来鉴别。将镍铬丝环在浓盐酸中清洗，沾取少量样品粉末，在蓝色火焰边缘灼烧。
Observe the flame colour quickly because some emissions are brief. Sodium ions give an intense yellow flame that can mask other colours; to see the lilac of potassium, use a blue cobalt glass to filter out the yellow light.
迅速观察火焰颜色，因为有些发光非常短暂。钠离子产生强黄色火焰，可能掩盖其他颜色；观察钾离子的淡紫色时，可使用蓝色钴玻璃滤去黄光。
The pH of a solution indicates its acidity or alkalinity. Universal indicator solution, pH paper, or a calibrated pH meter can all be used to measure pH. A pH below 7 is acidic, pH 7 is neutral, and above 7 is alkaline.
溶液的 pH 指示其酸碱度。可使用通用指示剂、pH 试纸或校准后的 pH 计来测量 pH。pH 小于 7 为酸性，等于 7 为中性，大于 7 为碱性。
When testing a large number of samples, pH paper is convenient: dip the strip into the solution and compare the colour to the chart provided. A pH meter gives the most precise digital reading, ideal for soil analysis or acid rain investigations.
测试大量样品时，pH 试纸较为便捷：将试纸浸入溶液，再与标样比色卡对比。pH 计能给出最精确的数字读数，非常适用于土壤分析或酸雨研究。
Always rinse the electrode of a pH meter with distilled water before and after each measurement. Store it in a suitable solution to prevent it from drying out.
每次测量前后均用蒸馏水冲洗 pH 计电极，并将其保存在适宜的溶液中，以防干燥。
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