📚 Year 9 CAIE Biology Practical Assessment Key Points | 九年级 CAIE 生物实验考核要点
Practical assessment in Year 9 CAIE Biology is not a memory test - it checks whether you can work safely in a laboratory, handle apparatus correctly, make accurate observations, record and present data properly, and evaluate your own experiment honestly. This guide walks through the core practical skills and the investigations that appear most often in Checkpoint papers and school-based practical exams, so you know exactly what to do and why.
九年级 CAIE 生物的实验考核不是背诵测试——它考查的是你能否在实验室中安全操作、正确使用仪器、做出准确观察、规范记录与呈现数据，并诚实地评价自己的实验。本指南梳理了核心实验技能以及 Checkpoint 试卷和校内实验考试中最常出现的探究活动，让你清楚每一步该做什么、为什么这样做。
1. Laboratory Safety and Good Practice | 实验室安全与良好规范
Always wear safety goggles and a lab coat when handling chemicals, biological specimens or heating substances. Safety equipment is part of the marks, not an optional extra.
在处理化学品、生物样本或加热物质时，务必佩戴护目镜和实验服。安全装备是得分点的一部分，而不是可有可无的附加项。
Tie back long hair and remove loose clothing or hanging jewellery to avoid catching fire or knocking over equipment. Keep your bench clear of bags, coats and unnecessary papers.
束起长发，取下宽松衣物或悬垂的首饰，以免着火或碰倒仪器。实验台上不要堆放书包、外套和无关纸张。
Never eat, drink or taste anything in the laboratory, even if a substance looks like food. Wash your hands with soap and water after completing practical work.
实验室里禁止饮食或品尝任何东西，即使某种物质看起来像食物。完成实验操作后，用肥皂和水洗手。
When heating liquids in a test tube, point the open end away from yourself and others, and use a water bath or a Bunsen burner with the correct flame. Never heat a closed container.
在试管中加热液体时，管口应远离自己和他人，并使用水浴或本生灯的正确火焰。绝不可加热密闭容器。
Report any breakages or spills immediately, and never clear broken glass with bare hands - use a dustpan and brush. Dispose of biological waste according to your teacher's instructions.
如有破损或溅洒，应立即报告；绝不可徒手清理碎玻璃，应使用簸箕和刷子。按照老师的要求处理生物废弃物。
2. Using a Light Microscope | 使用光学显微镜
Start with the lowest-power objective lens and use the coarse focus knob to bring the stage close to the lens, viewing from the side to avoid crushing the slide. Then look through the eyepiece and focus upwards slowly.
先从最低倍物镜开始，使用粗调焦旋钮使载物台靠近镜头，从侧面观察，以免压碎玻片。然后从目镜中观察，缓慢向上调焦。
Once the image is sharp under low power, rotate the nosepiece to the medium or high-power objective. Under high power use only the fine focus knob, because the coarse knob can drive the lens into the slide.
低倍镜下图像清晰后，转动转换器换到中倍或高倍物镜。高倍镜下只能使用细准焦旋钮，因为粗准焦旋钮可能使镜头撞到玻片。
Adjust the light with the mirror or the iris diaphragm so the field of view is bright but not dazzling. Clean lenses only with lens tissue - never with a paper towel or your sleeve.
用反光镜或光圈调节光线，使视野明亮但不刺眼。只能使用擦镜纸清洁镜头，绝不可用纸巾或衣袖。
Total magnification is calculated as:
总放大倍数的计算方法为：
Total magnification = eyepiece magnification × objective magnification
ve gives a total magnification of ×400. You also need to relate drawing size to real size:
例如 ×10 目镜配 ×40 物镜，总放大倍数为 ×400。你还需要把图的尺寸与真实尺寸联系起来：
Magnification = image size ÷ actual size
3. Preparing Slides and Staining | 制作装片与染色
For an onion epidermis slide, peel a thin, single layer of inner epidermis with forceps and lay it flat on a drop of water on the slide. Lower a cover slip at about 45° and lower it slowly to avoid trapping air bubbles.
制作洋葱表皮装片时，用镊子撕取一层薄薄的内部表皮，平铺在载玻片上的水滴中。盖玻片以约 45° 角缓慢放下，以免夹入气泡。
Add a drop of iodine solution to the edge of the cover slip and draw it through with blotting paper. Iodine stains the nucleus and makes starch-containing structures appear blue-black.
在盖玻片边缘滴一滴碘液，用吸水纸在另一侧吸引使其通过。碘液使细胞核着色，并使含淀粉的结构呈蓝黑色。
Methylene blue is used for animal cells such as cheek cells, staining the nucleus dark blue so it stands out against the pale cytoplasm. Always use a fresh, clean slide and never touch the centre of it with your fingers.
亚甲基蓝用于动物细胞（如口腔上皮细胞），使细胞核呈深蓝色，在浅色细胞质中更容易分辨。务必使用干净的新载玻片，不要用手指接触玻片中央。
When you draw what you see, use a sharp pencil, draw continuous single lines, add no shading, and label with straight, non-crossing lines that do not end in arrows. Always write the total magnification under the drawing.
绘观察图时，应使用削尖的铅笔、连续的单线，不涂阴影；标线要平直、互不交叉，且末端不加箭头。图下方必须写明总放大倍数。
4. Using a Bunsen Burner and Heating Techniques | 使用本生灯与加热技术
Check that the rubber tubing is firmly attached and free of cracks before turning on the gas tap. Light a match first, then turn on the gas and hold the match to the side of the barrel.
打开燃气阀前，先检查橡胶管是否牢固连接、有无裂缝。先点燃火柴，再打开燃气阀，把火柴放在灯管侧面点燃。
A yellow, luminous flame is cool and sooty. Open the air hole fully to produce a blue, roaring flame, which is hotter and is the flame you should use for heating.
黄色发光火焰温度低且冒烟。完全打开气孔可产生蓝色"呼呼"火焰，温度更高，是加热时应使用的火焰。
Hold a test tube in a test tube holder, tilt it away from yourself and others, and move it gently through the flame rather than holding it still. Never point the tube at a person.
用试管夹夹住试管，管口倾斜朝向远离自己和他人的方向，并在火焰中轻轻来回移动，而不是固定不动。绝不可把试管口对准他人。
Use a water bath when the substance is flammable or when a steady, gentle temperature is needed, for example when heating ethanol or when conducting food tests.
当物质易燃，或需要稳定温和的温度时，应使用水浴，例如加热乙醇或进行食物检验时。
5. Measuring and Using Apparatus | 测量与器材使用
When reading a measuring cylinder, place it on a flat surface and read the bottom of the meniscus at eye level. A tilted cylinder or a side-on view gives a parallax error.
读取量筒时，应将其放在水平面上，视线与凹液面最低点齐平。量筒倾斜或侧视都会造成视差误差。
For a thermometer, make sure the bulb is fully immersed in the liquid but does not touch the bottom or sides of the container, and wait for the reading to stabilise before recording.
使用温度计时，确保玻璃泡完全浸入液体，但不接触容器底部或侧壁，并等待读数稳定后再记录。
On a balance, press tare or zero the reading with the empty container on the pan, then add the substance. Record the mass to the precision shown, for example 2.45 g rather than 2 g.
使用天平时，先把空容器放在秤盘上并按去皮或归零，再加入物质。读数要记录到仪器显示的精密度，例如记作 2.45 g 而不是 2 g。
Remember that precision and accuracy are different ideas:
记住，精密度和准确度是两个不同的概念：
| Term | Meaning | 中文含义 |
| Accuracy | How close a reading is to the true value | 读数与真实值的接近程度 |
| Precision | How small the scale divisions of the instrument are | 仪器最小刻度的大小 |
6. Food Tests | 食物检验
Food tests use a specific reagent for each nutrient, and you must learn both the method and the positive result. Always use a clean test tube and label it before you start.
食物检验针对每种营养物质使用特定试剂，方法和阳性结果都必须掌握。开始前务必使用干净试管并做好标记。
| Nutrient | Reagent and method | Positive result | 中文 |
| Starch | Iodine solution, added at room temperature | Yellow-brown → blue-black | 淀粉：碘液，黄棕→蓝黑 |
| Reducing sugar | Benedict's solution, heated in a water bath at about 70-80 °C for 5 minutes | Blue → green → yellow → orange → brick red | 还原糖：本尼迪克特试剂，70-80 °C 水浴约 5 分钟，蓝→绿→黄→橙→砖红 |
| Protein | Biuret test: add dilute sodium hydroxide, then a few drops of copper(II) sulfate solution | Blue → purple or lilac | 蛋白质：双缩脲检验，加稀氢氧化钠后加几滴硫酸铜溶液，蓝→紫或淡紫 |
| Lipid | Ethanol emulsion test: shake with ethanol, then pour into water | Milky white emulsion | 脂质：乙醇乳化检验，与乙醇振荡后倒入水中，出现乳白色浑浊 |
Safety matters here: Benedict's solution and copper(II) sulfate contain harmful metal salts, and sodium hydroxide is corrosive, so wear goggles and wash any spill on skin immediately with plenty of water.
这里的安全问题很重要：本尼迪克特试剂和硫酸铜含对人体有害的金属盐，氢氧化钠有腐蚀性，因此必须戴护目镜，皮肤沾到应立即用大量清水冲洗。
When you report results, describe the actual colour you observed, not just "positive". A weak green or yellow is a low concentration of reducing sugar, while brick red shows a high concentration.
报告结果时，要描述你实际观察到的颜色，而不是只写"阳性"。淡绿或黄色表示还原糖浓度低，砖红色表示浓度高。
7. Testing a Leaf for Starch | 检测叶片中的淀粉
First boil the leaf in water for about one minute. This kills the cells and breaks down the cell membranes so that reagents can enter.
首先把叶片放入水中煮沸约一分钟。这能杀死细胞并破坏细胞膜，使试剂能够进入。
Next, turn off the Bunsen burner and place the leaf in boiling ethanol in a water bath. Ethanol is highly flammable, so it must never be heated directly over a flame. The leaf becomes pale and brittle as chlorophyll is removed.
接着关闭本生灯，把叶片放入水浴中加热的沸腾乙醇里。乙醇极易燃，绝不可直接用火焰加热。叶绿素被去除后，叶片变得苍白而脆硬。
Dip the decolourised leaf in hot water to soften it, then spread it on a white tile and add iodine solution. A blue-black colour shows that starch is present; a yellow-brown colour shows it is absent.
把脱色后的叶片浸入热水中软化，然后平铺在白瓷板上加碘液。呈蓝黑色说明含有淀粉；呈黄棕色说明不含淀粉。
In a photosynthesis investigation, a leaf that was covered with aluminium foil shows no blue-black colour because light was excluded, while an uncovered leaf turns blue-black. This shows light is needed for starch formation.
在光合作用探究中，用铝箔遮光的部位不出现蓝黑色，而未遮光部位变蓝黑色。这说明淀粉的形成需要光。
Afterwards, wash your hands and clear the ethanol away from any heat source. Always leave the plant in the dark for 24-48 hours before the test if you want to show that starch has been used up.
实验后要洗手，并把乙醇移离一切热源。若想证明原有淀粉已被消耗，测试前应先把植物放在暗处 24-48 小时。
8. Investigating Enzymes | 探究酶
A classic Year 9 investigation uses amylase to break down starch. Mix amylase solution with starch solution, then remove a drop every 30 seconds and test it on a white tile with iodine solution.
九年级经典探究之一是用淀粉酶分解淀粉。把淀粉酶溶液与淀粉溶液混合，每隔 30 秒取一滴放在白瓷板上用碘液检验。
The end point is the first sample that no longer turns blue-black. Record this time in seconds, and repeat the experiment to check reliability.
终点是第一个不再变蓝黑的样本。用秒记录这一时间，并重复实验以检验结果的可靠性。
The rate of reaction can be calculated from the time taken:
反应速率可由所用时间计算：
Rate = 1 ÷ time taken (s⁻¹)
To investigate temperature, stand the tubes in water baths at 10, 20, 30, 40 and 50 °C and keep everything else the same. Plot time on the y-axis against temperature on the x-axis and look for the optimum.
探究温度影响时，把试管分别放入 10、20、30、40 和 50 °C 的水浴中，并保持其他条件完全相同。以温度为横轴、时间为纵轴作图，寻找最适温度。
Controlled variables include the volume and concentration of starch and amylase, the pH (use a buffer solution), the temperature and the time interval between samples. Above about 60 °C the enzyme is denatured and the reaction stops.
控制变量包括淀粉和淀粉酶的体积与浓度、pH（使用缓冲液）、温度以及取样时间间隔。超过约 60 °C 时酶变性，反应停止。
9. Osmosis and Diffusion Investigations | 渗透与扩散探究
Cut potato cylinders of equal length using a cork borer and a ruler, blot them dry, and record the initial mass of each one. Handle them with forceps, not fingers, to avoid transferring salts.
用打孔器和尺子切出等长的马铃薯圆柱，用吸水纸吸干表面水分，记录每根的初始质量。用镊子拿取而不用手，以免带入盐分。
Place one cylinder in each sucrose solution (for example 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 mol dm⁻³) and leave them for at least 20 minutes. Then blot and reweigh.
把每根圆柱分别放入不同浓度的蔗糖溶液（例如 0.0、0.2、0.4、0.6、0.8 和 1.0 mol dm⁻³）中，静置至少 20 分钟，然后吸干并重新称重。
Calculate the percentage change in mass for each cylinder:
计算每根圆柱质量变化的百分比：
Percentage change = (final mass − initial mass) ÷ initial mass × 100%
Plot percentage change against sucrose concentration. The point where the line crosses zero shows the concentration at which the potato tissue neither gains nor loses water, which estimates the concentration of the cell contents.
以蔗糖浓度为横轴、质量变化百分比为纵轴作图。曲线与零线相交处的浓度，即马铃薯组织既不吸水也不失水的浓度，可用来估算细胞液的浓度。
A related demonstration uses Visking tubing filled with starch and glucose solution, placed in water. Glucose diffuses out and can be detected with Benedict's test, while starch is too large to pass through the partially permeable membrane.
一个相关演示是把装有淀粉和葡萄糖溶液的透析管放入水中。葡萄糖扩散出来，可用本尼迪克特检验检出；而淀粉分子太大，无法通过半透膜。
10. Gas Exchange and Respiration | 气体交换与呼吸
Hydrogencarbonate indicator is a sensitive test for carbon dioxide concentration: it is purple when carbon dioxide is low, red at atmospheric level, and yellow when carbon dioxide is high.
氢碳酸盐指示剂是检测二氧化碳浓度的灵敏试剂：二氧化碳浓度低时呈紫色，处于大气水平时呈红色，浓度高时呈黄色。
To show respiration, place germinating seeds in a sealed tube with hydrogencarbonate indicator. The indicator turns yellow as the seeds release carbon dioxide. Boiled seeds act as a control and the indicator stays red.
要证明呼吸作用，可把发芽的种子放入密闭管中并加入氢碳酸盐指示剂。种子释放二氧化碳，指示剂变黄。煮沸过的种子作为对照，指示剂保持红色。
For photosynthesis, place pondweed such as Elodea in water with a light source at different distances and count the bubbles of oxygen released per minute. Keep the temperature and the carbon dioxide concentration constant.
探究光合作用时，把黑藻等水生植物放入水中，在不同距离放置光源，记录每分钟释放的氧气气泡数。温度与二氧化碳浓度需保持恒定。
Remember the gas exchange equations behind these practicals:
记住这些实验背后的气体交换方程式：
Respiration: glucose + oxygen → carbon dioxide + water (+ energy)
Photosynthesis: carbon dioxide + water → glucose + oxygen (light + chlorophyll)
11. Recording, Presenting and Analysing Data | 记录、呈现与分析数据
Before you start, identify the independent variable (what you change), the dependent variable (what you measure) and the control variables (what you keep the same). Write them down in a plan table.
开始前先确定自变量（你改变的变量）、因变量（你测量的变量）和控制变量（你保持不变的变量），并列入实验计划表。
Draw a results table with a ruler and pencil. Put the independent variable in the first column and the dependent variable in the next, with the unit in the heading, for example "Time / s" or "Mass / g".
用尺子和铅笔绘制结果表。自变量放在第一列，因变量放在下一列，单位写在表头，例如 "Time / s" 或 "Mass / g"。
Record all raw readings, even the odd ones, then calculate means:
记录所有原始读数，包括看似异常的数据，然后计算平均值：
Mean = Σ of readings ÷ number of readings
On a graph, label both axes with quantity and unit, use a sensible scale, plot points with small crosses, and draw a single smooth curve or straight line of best fit. Do not join the dots point to point unless the question asks for it.
作图时，两轴都要标注物理量与单位，选择合理的刻度，用小的叉号描点，并画出单条平滑曲线或最贴合直线
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