📚 Experimental Skills for Edexcel IAL Chemistry Unit 1 (CH01) | 爱德思国际AS化学单元1（CH01）实验技能
Practical work forms the backbone of the International AS Chemistry qualification, and Unit 1 (CH01) assesses your understanding of essential laboratory techniques through written examination questions. Whether you are asked to describe how to make a standard solution, outline a titration procedure, or identify sources of error in a preparation, you need to be able to recall clear, step‑by‑step methods and explain the reasoning behind each action. This article covers all the important experimental operations that appear in Edexcel IAL Chemistry Unit 1, emphasising correct apparatus, measurement, heating, purification, and safety practices.
实验操作是国际AS化学课程的基石，单元1（CH01）通过笔试题目考查你对关键实验室技术的掌握。无论题目要求你描述如何配制标准溶液、概述滴定步骤，还是指出制备过程中的误差来源，你都需要回忆出清晰的分步方法并解释每一步的理由。本文涵盖了爱德思国际AS化学单元1中所有重要的实验操作，重点介绍正确的仪器使用、测量、加热、提纯和安全规范。
1. Introduction to Practical Work in Unit 1 | 单元1实验概论
The practical questions in Unit 1 are designed to test your knowledge of common procedures such as preparing a soluble salt, performing a titration, and measuring the volume of a gas. You should be able to name the apparatus, justify the choice of equipment, and describe the observations that confirm a reaction is complete. Marks are awarded for precise wording, so using key terms like ‘meniscus’, ‘tare’, ‘to constant mass’, and ‘swirl’ is essential.
单元1的实验题目旨在考查你对常见操作（如制备可溶性盐、进行滴定、测量气体体积）的理解。你需要能够说出仪器名称、说明选择某种设备的原因，并描述证明反应完全的实验现象。评分标准要求用语准确，因此使用“弯液面”、“去皮”、“恒重”、“旋转摇动”等关键词至关重要。
2. Accurate Measurement of Mass | 质量的精确测量
A digital balance reading to ±0.01 g or ±0.001 g is used for most quantitative work. Before weighing, press the tare button with an empty container on the pan to zero the balance. Solid samples are placed in a weighing boat or directly into a beaker. For hygroscopic solids that absorb moisture from the air, a stoppered weighing bottle should be used and the mass recorded quickly.
多数定量实验使用精度为±0.01 g或±0.001 g的电子天平。称量前，将空容器放在秤盘上按去皮键归零。固体样品放在称量舟中或称入烧杯。对于会从空气中吸收水分的易潮解固体，应使用带盖的称量瓶并快速记录质量。
When preparing a standard solution by dissolving a solid, the weighed solute is transferred into a beaker, dissolved in deionised water, and then transferred quantitatively into a volumetric flask. Any solid remaining in the beaker must be rinsed into the flask with washings three times to ensure a complete transfer.
通过溶解固体制备标准溶液时，称好的溶质转入烧杯，用去离子水溶解，然后定量转移至容量瓶中。烧杯中残留的固体必须用洗液冲洗三次，一并转入容量瓶，以确保完全转移。
3. Measuring Volumes: Pipettes and Burettes | 体积测量：移液管与滴定管
A volumetric pipette delivers a fixed volume, typically 25.0 cm³, with high accuracy (±0.06 cm³). After filling using a pipette filler, the solution is allowed to drain freely, and the last drop touched off against the inside of the receiving flask. Never blow out the pipette; the calibrated volume accounts for the small amount left in the tip.
单标移液管可精确移取固定体积（通常为25.0 cm³），准确度高达±0.06 cm³。用洗耳球吸取溶液后，让溶液自然流出，然后将尖端轻触接收容器内壁去掉最后一滴。切勿吹出移液管尖端残留的溶液，因为校准体积已包含这部分微量液体。
A burette is read from the bottom of the meniscus with the eye level at the meniscus to avoid parallax errors. The burette must be rinsed first with deionised water and then with the solution it will contain. The jet space below the tap must be filled and free of air bubbles before the initial reading is taken.
滴定管读数时需以弯液面底部为准，眼睛与弯液面保持水平以避免视差。滴定管须先用去离子水润洗，再用待装溶液润洗。读取初读数前，必须使旋塞下方的尖嘴充满溶液，不能有气泡。
4. Performing a Titration | 滴定操作
A titration begins with a rough trial to estimate the end‑point volume. The conical flask containing the analyte and a few drops of indicator is placed on a white tile, and the titrant is added from the burette with constant swirling. Near the end‑point, the titrant is added dropwise until a permanent colour change is observed.
滴定首先进行一次粗滴以估计终点体积。将盛有分析物与几滴指示剂的锥形瓶放在白色瓷砖上，边旋转摇动边从滴定管滴加滴定剂。接近终点时，一滴一滴地加入滴定剂，直到出现持久的颜色变化。
Three concordant titres (within ±0.10 cm³) are required for a reliable mean. If an air bubble is trapped in the jet during titration, the titre volume will be greater than the true volume, leading to systematic error. The burette should be refilled to the zero mark before each accurate titration.
需要三次相符的滴定读数（彼此相差≤±0.10 cm³）才能取平均值。如果滴定过程中尖嘴内有气泡，滴定体积将偏大，造成系统误差。每次精确滴定前都应将滴定管补加溶液至零刻度。
| Indicator | Colour in acid | Colour in alkali | pH range |
|---|---|---|---|
| Phenolphthalein | Colourless | Pink | 8.2–10.0 |
| Methyl orange | Red | Yellow | 3.1–4.4 |
5. Preparation of a Soluble Salt: Making Copper(II) Sulfate Crystals | 可溶性盐的制备：制取硫酸铜晶体
The classic preparation involves reacting excess copper(II) oxide with warm dilute sulfuric acid. An excess of the black solid ensures all the acid is neutralised. The mixture is heated gently with stirring; the reaction is complete when no more copper(II) oxide dissolves and the solution turns a clear blue colour.
经典的制备反应是使过量氧化铜与温热稀硫酸反应。过量黑色固体确保酸被完全中和。在搅拌下温和加热混合物；当不再有氧化铜溶解、溶液变为清亮的蓝色时，反应即完成。
The equation is:
CuO (s) + H₂SO₄ (aq) → CuSO₄ (aq) + H₂O (l)
After filtering off the unreacted solid, the blue filtrate is evaporated gently until a small volume remains and then left to crystallise. Large, well‑shaped crystals form on slow cooling. The crystals are collected by filtration, washed with a little cold deionised water, and dried by pressing between filter papers.
滤除未反应的固体后，将蓝色滤液缓慢蒸发至剩余少量体积，然后静置结晶。缓慢冷却能形成大而规则的晶体。通过过滤收集晶体，用少量冷去离子水洗涤，在滤纸之间压干。
6. Heating Techniques: Water Bath, Bunsen Burner, and Heating Under Reflux | 加热技术：水浴、本生灯与回流
Flammable organic solvents must never be heated with a direct flame. A water bath provides gentle, even heating and is ideal for evaporating aqueous solutions or for maintaining a temperature below 100 °C. When using a Bunsen burner, the blue flame should be applied with a tripod and gauze to spread the heat evenly.
易燃有机溶剂绝不能直接明火加热。水浴能提供温和均匀的加热，适用于蒸发水溶液或维持100 °C以下的温度。使用本生灯时，应在三脚架和石棉网上用蓝色火焰加热，以使热量均匀分布。
Heating under reflux is used to carry out a reaction at the boiling point of the solvent without loss of volatile components. The flask is fitted with a vertical condenser; vapours condense and drip back into the reaction mixture. Anti‑bumping granules are added to promote smooth boiling.
回流加热用于在溶剂沸点进行反应而不损失挥发性组分。烧瓶装配竖直冷凝管，蒸气冷凝后滴回反应混合物。需加入沸石（防暴沸颗粒）以促进平稳沸腾。
7. Filtration, Evaporation, and Crystallization | 过滤、蒸发与结晶
Gravity filtration through a fluted filter paper in a glass funnel is used to remove an insoluble solid from a liquid. The filtrate should be collected in a clean beaker. For hot filtration, the apparatus is pre‑warmed to prevent crystallisation in the funnel.
重力过滤使用放入玻璃漏斗中的折叠滤纸，用以从液体中分离不溶性固体。滤液应收集在洁净烧杯中。热过滤时需预热仪器，防止晶体在漏斗中析出。
Evaporation is carried out in an evaporating dish on a steam bath or gentle hot‑plate. For crystallisation, the solution is evaporated until a small volume remains, then allowed to cool. Scratching the inside of the beaker with a glass rod may induce crystallisation if none occurs spontaneously.
蒸发在蒸发皿中借助蒸气浴或温和热板进行。结晶时，溶液蒸发至剩余少量体积后静置冷却。若未自发结晶，可用玻璃棒刮擦烧杯内壁以诱发结晶。
8. Drying and Purification | 干燥与纯化
Filtered crystals are dried by pressing between two sheets of dry filter paper or left in a warm, dry place. Heating in an oven is possible only if the compound is thermally stable. A desiccator containing silica gel or anhydrous calcium chloride can be used to dry solids without heating.
过滤得到的晶体可在两张干燥滤纸间压干，或放在温暖干燥处晾干。只有在化合物热稳定的情况下才能用烘箱加热干燥。装有硅胶或无水氯化钙的干燥器可用于不加热干燥固体。
Recrystallisation is the main purification method for solid organic products and some inorganic salts. The impure solid is dissolved in the minimum volume of hot solvent, hot‑filtered if necessary, and then cooled slowly. The pure crystals form while soluble impurities remain in the mother liquor. A melting point determination can be used to confirm purity.
重结晶是固体有机产物和某些无机盐的主要提纯方法。将不纯固体溶于尽量少的热溶剂中，若需要则趁热过滤，然后缓慢冷却。纯晶体析出，而可溶性杂质留在母液中。熔点的测定可验证纯度。
9. Collecting and Measuring Gases | 气体的收集与测量
The volume of gas produced in a reaction can be measured using a gas syringe or by displacement of water in an inverted measuring cylinder. A gas syringe allows dry gases to be measured directly, while the water‑displacement method is suitable for gases that are insoluble or only slightly soluble in water, such as hydrogen and oxygen.
反应生成的气体体积可用气体注射器或通过倒置量筒排水法测量。气体注射器可直接测量干燥气体，而排水法适合不溶于或微溶于水的气体，如氢气和氧气。
Before starting, the apparatus must be checked for leaks. When using a gas syringe, the plunger should move smoothly; any sticking indicates a problem. All tubing connections must be tight. The initial volume should be noted before the reaction, and measurements taken at regular time intervals if studying rate.
实验开始前必须检查装置是否漏气。使用气体注射器时，活塞应能平滑移动，阻力变大表示有问题。所有管路连接必须紧密。在反应前记录初始体积，如果是研究反应速率，则应每隔固定时间记录数据。
10. Using Indicators and Choosing the Right One | 指示剂的使用与选择
Proper indicator selection depends on the pH range over which the colour change occurs and the pH at the equivalence point of the titration. For a strong acid–strong base titration, either phenolphthalein or methyl orange is suitable because the equivalence point lies near pH 7 and the vertical section of the pH curve covers the indicator’s range.
指示剂的恰当选择取决于其变色范围以及滴定等当点的pH。强酸强碱滴定中，酚酞和甲基橙都适用，因为等当点在pH 7附近，且pH突跃范围覆盖指示剂的变色区间。
For a weak acid with a strong base, phenolphthalein is preferred because the equivalence point is slightly alkaline. Methyl orange would change colour too early, before the equivalence point. Only a few drops of indicator are used; adding too much can itself affect the titre because indicators are weak acids or bases.
弱酸与强碱滴定时优选酚酞，因为等当点略呈碱性。甲基橙会在达到等当点之前就变色，过早指示。指示剂只用几滴即可；加入过多会因其本身是弱酸或弱碱而影响滴定体积。
11. Common Sources of Error and How to Minimize Them | 常见误差来源与减少方法
Systematic errors affect all readings in the same direction. Examples include using a burette with a faulty scale, misreading the meniscus consistently, or an air‑leak in the gas collection apparatus. These cannot be reduced by repeating the experiment but can be minimised by calibrating equipment and following a careful technique.
系统误差使所有读数朝同一方向偏离，例如使用刻度不准的滴定管、始终错误读取弯液面或气体收集装置漏气。重复实验不能减少系统误差，但可通过校准仪器和谨慎操作将其降到最低。
Random errors cause readings to be scattered around the true value. Reading the meniscus from a slightly different angle or small temperature fluctuations contribute to random error. These can be reduced by taking multiple readings and calculating a mean, and by ensuring the laboratory environment is stable.
随机误差导致读数分散在真实值周围。从略微不同的角度读取弯液面或微小的温度波动都会产生随机误差。多次读取并取平均值，以及保持实验环境稳定，可以减少随机误差。
Percentage uncertainty can be calculated for key measurements. For a 25.0 cm³ pipette with an uncertainty of ±0.06 cm³, the percentage uncertainty is (0.06 / 25.0) × 100 = 0.24%. For a mass of 2.50 g measured on a balance with ±0.01 g uncertainty, the percentage uncertainty is (0.01 / 2.50) × 100 = 0.40%. This helps identify the measurement that contributes most to the overall error.
关键测量的百分误差可以计算。一支25.0 cm³移液管，其不确定度±0.06 cm³，百分误差为(0.06 / 25.0) × 100 = 0.24%。若天平称量2.50 g，不确定度±0.01 g，百分误差为(0.01 / 2.50) × 100 = 0.40%。这有助于判断哪项测量对总误差贡献最大。
12. Safety in the Chemistry Laboratory | 化学实验室安全
All experimental descriptions in exam answers should mention relevant safety precautions. Eye protection must be worn at all times. When handling concentrated acids or alkalis, gloves should be used and the work carried out in a fume cupboard if fumes are evolved. Hair must be tied back and loose clothing secured.
所有考试答案中涉及实验描述时都应当提及相关的安全措施。必须始终佩戴护目镜。操作浓酸或浓碱时应戴手套，若产生有毒烟气则需在通风橱中进行。头发必须束起，宽松衣物要扎紧。
Specific hazards linked to Unit 1 experiments include the corrosiveness of sulfuric acid, the flammability of organic solvents such as ethanol when heating, and the toxicity of heavy‑metal compounds. If a question asks how to dilute concentrated acid, always state that the acid should be added slowly to water, not the reverse, while stirring and cooling.
单元1实验涉及的具体危险包括硫酸的腐蚀性、乙醇等有机溶剂在加热时的易燃性，以及重金属化合物的毒性。如果题目问如何稀释浓酸，一定要说明应将浓酸缓慢倒入水中并搅拌冷却，绝不能将水倒入酸中。
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