📚 IB CCEA Chemistry: A Guide to Experimental Techniques | IB CCEA 化学：实验操作指南
Mastering practical skills is essential for success in IB and CCEA Chemistry, where laboratory work reinforces theoretical concepts and develops scientific inquiry. This guide covers safe practices, fundamental techniques, and common experimental procedures that form the backbone of any chemistry course. Whether you are preparing for an internal assessment, a practical exam, or simply aiming to become a confident experimentalist, the following sections will provide clear, step‑by‑step instructions and bilingual explanations.
掌握实验技能是学好 IB 和 CCEA 化学的关键，实验不但能巩固理论知识，还能培养科学探究能力。无论你是在准备内部评估、实验考试，还是希望成为一名自信的实验者，这份指南都会通过清晰的分步讲解和双语对照，为你介绍实验室安全、基本操作以及常见的实验方法。
1. Safety & Laboratory Rules | 安全与实验室规则
Always wear a lab coat, safety goggles, and closed‑toe shoes. Tie back long hair and avoid loose clothing. Eating, drinking, and chewing gum in the lab are strictly forbidden. Know the location of the fire extinguisher, eyewash station, and first‑aid kit before starting any experiment.
进入实验室必须穿实验服、戴护目镜并穿包头鞋。长头发要扎好，不穿宽松衣物。实验室内严禁饮食、嚼口香糖。开始实验前，应熟悉灭火器、洗眼器和急救箱的存放位置。
Read the risk assessment for each chemical. Flammable liquids must be handled in a fume cupboard and kept away from open flames. Always pour acids into water, never water into acid, to prevent violent boiling. Dispose of waste in the correctly labelled containers — never pour organic solvents down the sink.
实验前要阅读每种化学品的风险评估。易燃液体必须在通风橱中使用，并远离明火。稀释浓酸时应将酸缓慢加入水中，不可反向操作，以防剧烈沸腾。废弃物要放入对应标签的容器中，有机溶剂绝不能倒入水槽。
2. Basic Measurement Techniques | 基本测量技术
Accurate mass measurements are made with an electronic balance. Record the mass to at least 0.01 g or 0.001 g depending on the balance. Always use a clean weighing boat or paper, and never place chemicals directly on the pan. Tare the balance before adding the sample.
精确称量使用电子天平，根据天平的精度记录至 0.01 g 或 0.001 g。称量时应使用干净的称量舟或称量纸，切勿将药品直接放在托盘上。加样前要按去皮键调零。
Liquids are measured with graduated cylinders, volumetric pipettes, or burettes, depending on the required precision. A graduated cylinder is sufficient for approximate volumes, while a volumetric pipette gives a fixed volume (e.g. 25.0 cm³) with high accuracy. Read the bottom of the meniscus at eye level to avoid parallax error.
量取液体可根据精度需求选用量筒、移液管或滴定管。量筒适用于粗略体积，移液管则可准确移取固定体积（如 25.0 cm³）。读数时视线应与凹液面最低处水平，以避免视差。
Volume delivered = final reading – initial reading
Temperature is measured with a thermometer (‑10 °C to 110 °C range, ±0.5 °C precision) or a digital temperature probe for faster response and data logging.
温度测量使用水银或酒精温度计（量程 ‑10 °C 至 110 °C，精度 ±0.5 °C），也可使用数字温度探头，响应更快并支持数据采集。
3. Heating Methods | 加热方法
The Bunsen burner is the standard heat source. Use a blue roaring flame (air hole fully open) for strong heating, and a yellow safety flame (air hole closed) when the burner is not in immediate use. Heat flammable liquids only in a water bath or with an electric heating mantle to avoid ignition.
本生灯是标准热源。强热时使用蓝色火焰（气孔全开），暂时不用时调至黄色安全焰（关闭气孔）。加热易燃液体必须用水浴或电热套，严禁直接明火加热。
Water baths provide gentle, uniform heating up to 100 °C. They are ideal for organic preparations that require controlled temperature. An electric hot plate with a magnetic stirrer allows simultaneous heating and stirring, improving temperature uniformity and reaction rate.
水浴可提供温和均匀的加热，最高可达 100 °C。它适用于需要控温的有机合成。电热板配合磁力搅拌器可同时加热和搅拌，使温度更均匀、反应更快。
Always use a clamp stand and a tripod with wire gauze when heating a beaker or flask over a Bunsen burner. Never heat a sealed container — it may explode. Point the mouth of a test tube away from yourself and others when heating its contents.
在本生灯上加热烧杯或烧瓶时，务必使用铁架台、三脚架和石棉网。不能加热密闭容器，否则可能爆炸。加热试管内容物时，管口应朝向无人处。
4. Separation & Purification Techniques | 分离与纯化技术
Filtration separates an insoluble solid from a liquid. Flute a filter paper and place it in a funnel. Pour the mixture slowly down a glass rod to prevent splashing. The solid collected on the paper is the residue; the liquid passing through is the filtrate. For hot filtration, pre‑heat the funnel and use a fluted paper to speed up the process.
过滤用于分离不溶性固体和液体。将滤纸折叠成扇状放入漏斗，混合物沿玻璃棒缓慢倾入以防飞溅。滤纸上收集的固体叫残渣，透过的液体叫滤液。热过滤时需预热漏斗并使用折叠滤纸以加快速度。
Evaporation and crystallisation are used to obtain a soluble solid from a solution. Gently heat the solution in an evaporating dish to concentrate it until crystals begin to form at the edge (the crystallisation point). Then allow it to cool slowly. Collect the crystals by filtration, wash with a little cold solvent, and dry between sheets of filter paper.
蒸发和结晶用于从溶液中获得可溶性固体。将溶液置于蒸发皿中缓慢加热浓缩，直至边缘出现晶膜（结晶点）。随后自然冷却，过滤收集晶体，用少量冷溶剂洗涤，最后用滤纸吸干。
Simple distillation separates a solvent from a solution or separates liquids with boiling points that differ by more than 25 °C. The thermometer bulb should be placed at the junction of the side arm to measure the vapour temperature. Anti‑bumping granules provide smooth boiling.
简单蒸馏用于分离溶剂与溶液或沸点相差 25 °C 以上的液体。温度计水银球应正对侧管接口处，以测量蒸气温度。加入沸石可防止暴沸。
Paper chromatography separates small quantities of dissolved substances. Draw a pencil baseline 2 cm from the bottom of the paper, spot the sample, and place the paper in a suitable solvent so that the baseline is above the solvent level. When the solvent front has risen close to the top, remove the paper, mark the front, and calculate Rf values: Rf = distance moved by spot ÷ distance moved by solvent front.
纸色谱用于分离少量溶解物质。在距底端 2 cm 处用铅笔画基线，点样后放入溶剂，基线要高于液面。当溶剂前沿接近顶端时取出，标记前沿位置，计算 Rf 值：Rf = 斑点移动距离 ÷ 溶剂前沿移动距离。
5. Titration Technique | 滴定技术
Titration is a quantitative technique for determining the concentration of an unknown solution. Both acid‑base and redox titrations (e.g. using potassium manganate(VII)) follow the same core procedure. A burette is rinsed first with deionised water and then with the solution it will contain. The conical flask should be clean but can be wet with water, as water does not alter the number of moles of the analyte.
滴定是一种测定未知溶液浓度的定量技术。酸碱滴定和氧化还原滴定（如使用高锰酸钾 KMnO₄）遵循相同的核心步骤。滴定管先用水润洗，再用待装溶液润洗；锥形瓶只需清洁，可用水湿润，因为水不会改变待测物质的物质的量。
Fill the burette and record the initial reading to the nearest 0.05 cm³. Use a white tile under the flask to detect the endpoint colour change clearly. Swirl the flask continuously while adding the titrant drop by drop near the endpoint. Repeat until two concordant titres (within 0.10 cm³) are obtained.
装液后记录初始读数，估读到 0.05 cm³。锥形瓶下放白瓷板以便观察终点颜色变化。接近终点时逐滴加入滴定剂，同时不停摇动锥形瓶。重复滴定至获得两次相差不超过 0.10 cm³ 的契合结果。
n = c × V (in dm³)
Record all readings in a table and calculate the mean titre from the concordant results. For acid‑base titrations using phenolphthalein, the endpoint is from pale pink to colourless (or vice versa). For manganate(VII) titrations, the endpoint is the first permanent pale pink colour — no indicator is needed because MnO₄⁻ acts as its own indicator.
将所有读数记录在表格中，用契合结果计算平均滴定体积。使用酚酞的酸碱滴定终点为淡粉色变无色（或反之）。高锰酸钾滴定中，终点是出现的第一抹持久淡粉色——无需额外指示剂，因为 MnO₄⁻ 自身作指示剂。
6. Gas Collection & Measurement | 气体收集与测量
Gases that are insoluble or slightly soluble in water, such as hydrogen, oxygen, and carbon dioxide, can be collected by downward displacement of water. Fill a gas jar completely with water, invert it into a water trough, and bubble the gas through the delivery tube. The gas rises and displaces the water. When full, a glass plate is slid under the jar before removing it from the trough.
不溶于或微溶于水的气体（如氢气、氧气、二氧化碳）可用排水集气法收集。将集气瓶装满水，倒扣入水槽中，导气管将气体通入瓶内。气体上升，将水排出。集满后用玻璃片盖住瓶口再移出水面。
Gases denser than air (e.g. Cl₂, HCl, SO₂) are collected by upward delivery, as they sink and displace air downwards. Gases less dense than air (e.g. NH₃, H₂) are collected by downward delivery, with the collecting vessel inverted. Always work in a fume cupboard when collecting toxic gases.
比空气密度大的气体（如 Cl₂、HCl、SO₂）用向上排空气法收集，它们会沉底并将空气向上排出。比空气轻的气体（如 NH₃、H₂）用向下排空气法，集气瓶倒置。收集有毒气体必须在通风橱内操作。
To measure the volume of a gas evolved in a reaction, attach a gas syringe or an inverted burette filled with water. Record the volume at regular time intervals if studying reaction kinetics. Correct for atmospheric pressure and temperature if absolute moles are required, although for rate comparisons the raw volume data often suffice.
测量反应生成的气体体积，可连接气体注射器或倒置的充水滴定管。研究动力学时每隔一定时间记录体积。如需计算物质的量，应对气压和温度进行校正；但在比较速率时，原始体积数据往往已经足够。
7. Reaction Rate Experiments | 反应速率实验
A typical rate experiment examines how concentration, temperature, or surface area affects the speed of a reaction. For the sodium thiosulfate and hydrochloric acid reaction (producing a sulfur precipitate), the time for a cross drawn on paper to ‘disappear’ is recorded. Keep the volume of the conical flask and the total volume constant to ensure fair testing.
典型的速率实验研究浓度、温度或表面积对反应快慢的影响。硫代硫酸钠与盐酸反应会生成硫沉淀，记录烧杯下“十字”消失所需的时间。要保持锥形瓶规格和溶液总体积一致，以确保公平测试。
Rate ∝ 1/time (for a fixed change)
For reactions that produce a gas, measure the volume of gas collected at set intervals. Plot a graph of volume against time. The initial rate is proportional to the gradient of the tangent at t = 0. Compare initial rates under different conditions to deduce the rate law. Always start timing the moment the reagents are mixed and swirl continuously unless the procedure states otherwise.
对有气体生成的反应，可定时测量收集到的气体体积，并绘制体积‑时间图。初始速率与图中 t = 0 处切线的斜率成正比。比较不同条件下的初始速率可推导速率方程。计时应从试剂混合那一刻开始，除非方案另有说明，否则反应过程中要持续搅拌。
8. Preparing Inorganic Compounds | 无机化合物的制备
A classic synthesis is the preparation of hydrated copper(II) sulfate crystals from copper(II) oxide and dilute sulfuric acid. Add excess copper(II) oxide to warm dilute sulfuric acid while stirring. The reaction is complete when no more black solid dissolves. Filter the mixture to remove excess CuO, then heat the blue filtrate to evaporate some water until the crystallisation point is reached. Leave the solution to cool slowly; large blue crystals of CuSO₄·5H₂O form. Dry the crystals between filter papers.
一个经典合成实验是用氧化铜与稀硫酸制备五水硫酸铜晶体。将过量的黑色氧化铜加入温热的稀硫酸中，不断搅拌，直至黑色固体不再溶解，反应完全。过滤除去过量 CuO，将蓝色滤液加热蒸发至结晶点，然后缓慢冷却，即可得到大颗粒的蓝色 CuSO₄·5H₂O 晶体。用滤纸吸干。
When preparing a salt by precipitation, such as lead(II) iodide, mix stoichiometric solutions of lead(II) nitrate and potassium iodide. A bright yellow precipitate forms immediately. Filter using a Buchner funnel under reduced pressure for faster drying. Wash with a small amount of cold distilled water and allow to dry.
用沉淀法制备盐（如碘化铅 PbI₂）时，将计量比的硝酸铅溶液与碘化钾溶液混合，立即产生亮黄色沉淀。用布氏漏斗抽滤可加快干燥速度。用少量冷蒸馏水洗涤后晾干。
Always calculate the percentage yield. For the CuSO₄ preparation, measure the mass of the dry crystals obtained and compare with the theoretical yield based on the limiting reactant (CuO).
一定要计算产率。以制备硫酸铜为例，称量干燥晶体质量，根据限制反应物（氧化铜）计算理论产量，然后求百分比产率。
Percentage yield = (actual mass ÷ theoretical mass) × 100%
9. Preparing & Purifying Organic Compounds | 有机物的制备与纯化
The synthesis of aspirin (acetylsalicylic acid) from salicylic acid and ethanoic anhydride is a common organic practical. Salicylic acid is reacted with an excess of ethanoic anhydride with a few drops of concentrated phosphoric acid as a catalyst. The mixture is heated in a water bath at 70–80 °C for about 15 minutes. After cooling, the product is precipitated by adding cold water and scratching the flask with a glass rod.
从水杨酸和乙酸酐合成阿司匹林（乙酰水杨酸）是有机实验中常见的操作。水杨酸与过量乙酸酐在几滴浓磷酸催化下反应，混合物在 70–80 °C 水浴中加热约 15 分钟。冷却后加入冷水并用玻璃棒摩擦瓶壁，使产品析出。
Purification involves recrystallisation from a suitable solvent (often ethanol/water mixture). The impure solid is dissolved in the minimum volume of hot solvent. The hot solution is filtered if necessary, then allowed to cool slowly. Pure crystals are collected by suction filtration, washed with a little cold solvent, and dried. Purity is checked by measuring the melting point; a pure sample of aspirin melts sharply at 138–140 °C, while impurities lower and broaden the melting range.
纯化步骤通常包括重结晶。将粗产物溶解在最少量的热溶剂（常用乙醇/水混合液）中，必要时趁热过滤，然后缓慢冷却。抽滤收集纯晶体，用少量冷溶剂洗涤后干燥。纯度通过熔点测定检查：纯阿司匹林熔点尖锐，位于 138–140 °C；杂质会降低并加宽熔程。
Liquid organic products, such as esters, are purified by distillation. Wash the impure ester with sodium carbonate solution to remove unreacted acid, then with water. Dry the organic layer over anhydrous magnesium sulfate, decant, and distill, collecting the fraction boiling at the expected temperature.
液态有机产物（如酯类）用蒸馏法纯化。先用碳酸钠溶液洗涤粗酯以除去未反应的酸，再用水洗。有机层用无水硫酸镁干燥，倾析后进行蒸馏，收集预期沸点范围内的馏分。
10. Data Recording & Error Analysis | 数据记录与误差分析
All experimental data must be recorded in ink directly into a bound laboratory notebook, never on loose sheets. Record values with the appropriate number of significant figures, reflecting the precision of the instrument. Use a ruler when drawing tables, and label each row and column with quantity, unit, and uncertainty where relevant.
所有实验数据必须用墨水直接记录在装订好的实验记录本上，绝不可记在散页纸上。记录时要使用与仪器精度相符的有效数字位数。画表时用直尺，每行每列都要标注物理量、单位及相应的不确定度。
Identify systematic errors (e.g. incorrectly calibrated balance, heat loss) and random errors (e.g. variations in reading the meniscus). Minimise random errors by repeating measurements and calculating the mean. Systematic errors are harder to detect and can be reduced by calibrating instruments or by running a blank determination. In a titration, subtracting a blank titre can correct for the volume needed to change the indicator colour.
识别系统误差（如未校准的天平、体系热量散失）和随机误差（如判读弯月面时的偏差）。通过重复测量和计算平均值可降低随机误差。系统误差较难发现，可通过校准仪器或进行空白实验来减小。滴定中扣除空白值，可校正指示剂变色所消耗的体积。
Estimate the percentage uncertainty of a measurement: for a burette reading (±0.05 cm³), the percentage uncertainty = (0.05 ÷ volume) × 100%, and for a single reading this is doubled because two readings are taken. Propagate uncertainties through calculations to assess the overall reliability of the result.
估算测量值的百分不确定度：对于滴定管读数（±0.05 cm³），百分不确定度 = (0.05 ÷ 体积) × 100%，且因需要两次读数，总不确定度需乘以 2。通过计算传播不确定度，可以评估最终结果的可靠性。
11. Common Laboratory Apparatus | 常见仪器及其使用
| Apparatus | Main Use / 主要用途 | Key Point / 关键点 |
|---|---|---|
| Volumetric flask / 容量瓶 | Preparing a solution of exact concentration / 配制准确浓度溶液 | Match the meniscus exactly to the graduation mark / 凹液面与刻度线相切 |
| Pipette / 移液管 | Delivering a fixed volume of liquid / 移取固定体积液体 | Rinse with the solution to be used; use a pipette filler / 用待移液润洗；使用洗耳球 |
| Burette / 滴定管 | Dispensing variable, measured volumes / 可变量液，用于滴定 | Read at eye level; remove air bubbles from the tip / 平视读数；排出尖嘴处气泡 |
| Desiccator / 干燥器 | Cooling and storing dry solids / 冷却和保存干燥固体 | Grease the seal; keep desiccant fresh / 密封用凡士林涂抹；干燥剂保持有效 |
| Reflux condenser / 回流冷凝管 | Heating organic reactions without loss of volatile solvent / 加热有机物反应时不损失挥发溶剂 | Water in at the bottom, out at the top / 冷却水下进上出 |
Other essential items include a crucible and lid for heating solids strongly, a Bunsen burner with a blue flame for high temperatures, and a glass stirring rod. Always select the right size of apparatus for the scale of your experiment.
其他必备物品包括用于强热固体的坩埚和坩埚盖、提供高温蓝色火焰的本生灯以及玻璃搅拌棒。始终根据实验规模选择合适尺寸的仪器。
12. General Good Practice | 一般实验规范
Always plan your experiment in advance. Prepare a clear method and a blank results table before entering the lab. This minimises time‑wasting and reduces the chance of mistakes. Work methodically, keeping the bench tidy and free of clutter. Clean all glassware immediately after use to avoid dried‑on residues.
实验前一定要制定计划。进入实验室前准备好清晰的实验步骤和空白结果表格，这样能节省时间、减少错误。操作要有条理，保持实验台整洁，用完的玻璃仪器立即清洗，避免残留物干结。
When recording observations, be specific: ‘the solution turned from orange to green’ is more informative than ‘colour changed’. Note the exact conditions, such as the temperature, pressure, or the addition of a catalyst. All these details are invaluable when evaluating the experiment and writing the lab report.
记录现象时要具体：比如“溶液由橙色变为绿色”比“颜色改变”提供了更多信息。记录精确的实验条件，如温度、压强或是否加入催化剂。这些细节在评估实验和撰写实验报告时极有价值。
Finally, never rush the practical work. Careful technique yields reliable data and develops the hands‑on skills that both IB and CCEA examiners expect to see reflected in your understanding and write‑ups.
最后，实验操作不可急躁。细心规范的操作才能获得可靠数据，并培养出扎实的动手能力——这正是 IB 和 CCEA 考官期望在你的理解和实验报告中看到的。
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