📚 Year 9 CAIE Chemistry: Practical Assessment Key Points | Year 9 CAIE 化学：实验/实践考核要点
In Year 9 CAIE Chemistry, practical assessments test your ability to work safely, handle apparatus with confidence, make accurate observations, record and process data, and draw valid conclusions. Mastering these skills will not only boost your exam performance but also build a strong foundation for IGCSE practical work. This guide walks you through every key aspect – from Bunsen burner use to graph drawing and error analysis.
在 Year 9 CAIE 化学课程中，实践考核重点考察你安全操作、熟练使用仪器、准确观察现象、记录与处理数据以及得出有效结论的能力。掌握这些技能不仅能提升考试成绩，还能为 IGCSE 阶段的实验工作奠定扎实基础。本指南将逐一梳理所有关键环节——从本生灯使用到图表绘制与误差分析。
1. Safety in the Laboratory | 实验室安全
Safety is the absolute priority in any practical exam. Always wear eye protection (goggles), a lab coat, and secure long hair. Know the location of the fire extinguisher, fire blanket, eyewash station, and emergency exits. Never eat, drink, or run in the laboratory. When handling chemicals, read labels carefully and use the smallest amounts possible. Familiarise yourself with common hazard symbols: flammable, corrosive, toxic, and irritant. If a chemical spill occurs, inform the teacher immediately.
安全是所有实验考核的首要前提。你必须始终佩戴护目镜、穿着实验服，并将长发束好。牢记灭火器、灭火毯、洗眼器和紧急出口的位置。严禁在实验室内饮食或奔跑。拿取化学品时要仔细阅读标签，并尽量使用最少量。熟悉常见的危险符号：易燃、腐蚀性、有毒和刺激性。一旦发生化学品泄漏，应立即报告教师。
Always wash your hands after practical work, even if you wore gloves. Never return unused chemicals to their original containers to avoid contamination. Use a fume cupboard when handling volatile or toxic gases, as instructed. Report any broken glassware or accidents straight away.
实验操作后一定要洗手，即使戴了手套。切勿将未用完的化学品倒回原瓶，以防污染。按要求在通风橱内处理挥发性或有毒气体。任何玻璃器皿破损或意外都要立刻上报。
2. Using a Bunsen Burner | 使用本生灯
The Bunsen burner is a fundamental heating tool. You must be able to light it safely and adjust the flame. A yellow flame (air hole closed) is luminous, sooty, and cooler; it is used for gentle heating or when not actively heating. A blue flame (air hole open) is roars, non-luminous, and much hotter – it is used for most heating tasks. To light the burner:
本生灯是最基本的加热工具。你必须能够安全地点燃它并调节火焰。黄色火焰（空气孔关闭）明亮、产生烟灰且温度较低，用于温和加热或待机状态。蓝色火焰（空气孔打开）呼呼作响、无光且温度高得多，适用于多数加热操作。点燃本生灯的步骤：
- Connect the gas tubing securely to the gas tap.
- Close the air hole fully.
- Light a splint and hold it just above the barrel, then turn on the gas tap.
- Gradually open the air hole until a steady blue flame is achieved.
- 将燃气管牢固地接在气阀上。
- 完全关闭空气孔。
- 点燃木条并将其放在管口上方，然后打开气阀。
- 逐渐打开空气孔，直至获得稳定的蓝色火焰。
Never leave a lit burner unattended. When not heating, turn off the gas or switch to a yellow safety flame. Always tie back long hair and tuck in ties before lighting the burner.
切勿让点燃的本生灯无人看管。不加热时，应关闭燃气或调至黄色安全火焰。点灯前务必束好长发、塞好领带。
3. Measuring Mass and Volume | 测量质量和体积
To measure mass, use an electronic balance. Always place a weighing boat or paper on the pan first, then press 'tare' (zero) before adding the substance. Do not place chemicals directly onto the balance pan. Record the mass with the appropriate number of decimal places as shown on the display.
使用电子天平测量质量。务必先在称量盘上放置称量舟或称量纸，按下“去皮”（归零）键，然后加入物质。切勿将化学品直接放在天平盘上。记录质量时要保留显示屏上所有的有效小数位数。
To measure liquid volumes, use a measuring cylinder (for rough volumes), a burette (for accurate dispensing), or a pipette (for precise fixed volumes). When reading a measuring cylinder, place it on a flat surface and bring your eyes level with the bottom of the meniscus. Always read the scale at eye level to avoid parallax error. Record volumes to the nearest half of the smallest division (e.g. to 0.5 cm³ if the scale marks every 1 cm³).
测量液体体积时，使用量筒（粗略体积）、滴定管（精确滴加）或移液管（精准固定体积）。读取量筒时，应将其放在平整桌面上，视线与弯月面最低点保持水平。始终在视线水平高度读取刻度，避免视差误差。体积记录精确到最小刻度的一半（如每隔 1 cm³ 刻度的量筒，记录到 0.5 cm³）。
4. Measuring Temperature and Time | 测量温度和时间
A thermometer should be treated with care – never stir solutions with a thermometer, as it can break. When measuring temperature, immerse the bulb fully in the liquid or the centre of the heated area without touching the container sides. Wait until the reading stabilises before recording. Use a digital thermometer or data logger when possible for higher precision.
温度计需小心使用——切勿用温度计搅拌溶液，以免破裂。测量温度时，应将感温泡完全浸入液体或置于加热区域中央，不要接触容器壁。等读数稳定后再记录。可能的情况下使用数字温度计或数据记录器以获得更高精度。
For timing, use a stopwatch or timer on a device. Start timing as soon as you mix reagents or apply heat, and record time to the nearest second. If an experiment requires repeated readings at set intervals (e.g. every 30 seconds), plan ahead so you can call out the readings while a partner records them in the table.
计时使用秒表或设备的计时功能。混合试剂或开始加热时立即启动计时，时间记录到秒。如果实验需按固定间隔（如每 30 秒）读数，应提前规划，可以一人报数、另一人将数据记录在表格中。
5. Filtration and Evaporation | 过滤与蒸发
Filtration separates an insoluble solid from a liquid. Fold a filter paper into a cone, place it in a filter funnel, and moisten it slightly with distilled water so it sticks to the funnel. Pour the mixture slowly down a glass rod into the funnel to avoid splashing. The solid (residue) stays in the paper, while the liquid (filtrate) passes through.
过滤可将不溶性固体从液体中分离。将滤纸折成圆锥形，放入漏斗中，用蒸馏水稍加润湿使其贴紧。使用玻璃棒引流，缓慢将混合物沿玻璃棒倒入漏斗以防飞溅。固体（滤渣）留在滤纸上，液体（滤液）则透过滤纸。
Evaporation is used to obtain a soluble solid from a solution. Pour the solution into an evaporating dish and heat gently over a water bath or on a tripod and gauze. Stop heating when the volume is much reduced and crystals just start to form; leave the rest to cool and crystallise slowly. Never heat to complete dryness, as some solids decompose or sputter.
蒸发用于从溶液中获得可溶性固体。将溶液倒入蒸发皿中，放在水浴锅或三脚架和石棉网上缓缓加热。当溶液体积明显减少、晶体开始析出时停止加热，任其自然冷却结晶。切勿蒸干，因为某些固体会分解或飞溅。
6. Simple Distillation | 简单蒸馏
Simple distillation separates a liquid from a solution (e.g. pure water from inky water) or two liquids with very different boiling points. The apparatus involves a round-bottom flask, a delivery tube connected to a condenser, and a receiving flask. The thermometer bulb must be positioned at the opening of the side arm (the vapor exit) to measure the temperature of the vapour accurately.
简单蒸馏用于从溶液中分离液体（如从墨水中制取纯水）或沸点相差很大的两种液体。装置包括圆底烧瓶、连接冷凝器的导管和接收瓶。温度计感温泡必须放在支管口（蒸气出口）处，以准确测量蒸气温度。
Cooling water enters the condenser jacket from the bottom and exits from the top, ensuring the jacket is always full of cold water. Heat the flask gently; the liquid with the lower boiling point vaporises first, condenses in the cooling jacket, and drips into the receiver as distillate. Keep the receiver well away from the flame.
冷却水从冷凝管外套的下口进入、从上口流出，以确保夹套始终充满冷水。用小火温和加热烧瓶；沸点较低的液体首先汽化，在冷凝管中冷凝，以溜分形式滴入接收瓶。接收瓶要远离火焰放置。
7. Chromatography | 色谱法
Paper chromatography separates small amounts of soluble coloured substances, such as dyes in ink. Use a pencil to draw a base line about 1.5 cm from the bottom of the chromatography paper – never use ink, because it will separate along with the sample. Place a small spot of the mixture on the baseline using a fine capillary tube. Allow the spot to dry and repeat to build up a concentrated spot.
纸色谱法可分离少量有色可溶物质，例如墨水中的染料。用铅笔在距色谱纸底端约 1.5 cm 处画一条起始线——切勿用墨水，因为它会与样品一同展开。用毛细管在基线上点一小点混合物，待斑点干燥后重复点样，以积聚一个较浓的斑点。
Suspend the paper in a beaker with the solvent level below the pencil line. The solvent travels up the paper, carrying the dyes at different rates. When the solvent front is near the top, remove and mark the front with a pencil. The Rf value can be calculated to identify substances:
将纸悬在烧杯中，溶剂液面必须低于铅笔线。溶剂沿纸上升，以不同速率携带染料。当溶剂前沿接近顶部时取出，用铅笔标出前沿位置。可通过计算 Rf 值来鉴定物质：
Rf = distance moved by the spot / distance moved by the solvent front
Rf = 斑点移动距离 / 溶剂前沿移动距离
Rf values are always less than 1 and have no units. Identical substances show the same Rf under identical conditions.
Rf 值总小于 1 且没有单位。相同物质在相同条件下表现出相同的 Rf 值。
8. Testing pH with Indicators | 用指示剂测试 pH
pH is a measure of acidity or alkalinity. Universal indicator solution or paper gives a range of colours depending on pH. For accurate measurements, add a few drops of universal indicator to a small sample of the solution, mix, and compare the colour to the provided chart. Alternatively, dip a clean glass rod into the test solution and touch it onto a piece of universal indicator paper. Red litmus paper turns blue in alkalis; blue litmus paper turns red in acids.
pH 是酸度或碱度的量度。通用指示剂溶液或试纸根据 pH 显示一系列颜色。为了准确测量，向少量待测液中滴加几滴通用指示剂，摇匀后与比色卡对照。也可将洁净的玻璃棒浸入待测液，然后点在通用指示剂试纸上。红色石蕊试纸遇碱变蓝，蓝色石蕊试纸遇酸变红。
| pH range | Colour with universal indicator | Nature |
| 0–3 | Red | Strong acid |
| 4–6 | Orange/yellow | Weak acid |
| 7 | Green | Neutral |
| 8–10 | Blue | Weak alkali |
| 11–14 | Purple/violet | Strong alkali |
| pH 范围 | 与通用指示剂的颜色 | 性质 |
| 0–3 | 红色 | 强酸 |
| 4–6 | 橙色/黄色 | 弱酸 |
| 7 | <
