📚 Year 7 OCR Biology: Practical Skills and Experiment Essentials | 七年级 OCR 生物：实验与实践考核要点
In Year 7 OCR Biology, practical skills carry as much weight as the facts you learn. You will be expected to handle apparatus safely, make precise observations, record results systematically, and evaluate your own experiments. This revision guide covers every key practical assessment point you are likely to meet – from using a microscope to testing for starch, controlling variables and drawing graphs.
在七年级 OCR 生物课程中，实验技能和你学到的理论知识同等重要。你需要在考核中安全地使用仪器、准确观察、系统记录结果，并评估自己的实验。本复习指南涵盖了你可能会遇到的每一个关键实验考核要点——从显微镜的使用到淀粉检测、控制变量以及绘制图表。
1. Safety in the Laboratory | 实验室安全
Always wear safety goggles whenever you are handling chemicals, heating substances or using a Bunsen burner. Goggles protect your eyes from splashes, fumes and hot particles.
在处理化学品、加热物质或使用本生灯时，始终要佩戴护目镜。护目镜可以保护你的眼睛免受飞溅液体、烟雾和高温颗粒的伤害。
Tie back long hair and tuck in any loose clothing, ties or scarves. This reduces the risk of them catching fire or dipping into chemicals.
将长发束起，把宽松的衣物、领带或围巾塞好。这样可以降低头发或衣物被点燃或沾到化学品的风险。
Never eat or drink in the laboratory, and always wash your hands after practical work. Some substances can be harmful even if they look harmless.
实验室内绝对禁止饮食，实验结束后务必洗手。有些物质看似无害，但实际上可能有害。
When heating a test tube, point its open end away from yourself and others. Use a test tube holder and heat gently, moving the tube continuously through the flame.
加热试管时，要将试管口指向远离自己和他人的方向。使用试管夹，温和加热，并使试管在火焰中不断移动。
2. Using a Microscope | 使用显微镜
A light microscope has an eyepiece lens (usually 10x magnification) and objective lenses (often 4x, 10x and 40x). Total magnification is calculated by multiplying the eyepiece magnification by the objective lens magnification.
光学显微镜配有目镜（通常放大10倍）和物镜（常见为4倍、10倍和40倍）。总放大倍数等于目镜放大倍数乘以物镜放大倍数。
Always start with the lowest power objective lens. Use the coarse focus knob to bring the stage close to the lens while looking from the side, then look through the eyepiece and focus slowly away until the image appears.
始终从最低倍物镜开始使用。从侧边看着物镜，用粗调焦旋钮让载物台靠近镜头，然后通过目镜观察，缓慢调焦直到图像清晰。
Once the specimen is roughly focused, use the fine focus knob to get a sharp image. Never use the coarse focus knob with the high power lens – it can crack the slide and damage the lens.
当标本大致对焦后，用细调焦旋钮获得清晰图像。使用高倍物镜时，切勿使用粗调焦旋钮，否则可能压碎玻片并损坏镜头。
Handle slides by their edges and keep lenses clean. If the image is too dark, adjust the mirror or light source and open the diaphragm.
手持玻片时只接触边缘，并保持镜头清洁。如果图像太暗，可以调节反光镜或光源，并打开光圈。
3. Preparing a Wet Mount Slide | 制作临时装片
To observe onion epidermis cells, peel a very thin layer of tissue from the inside of an onion scale. Use forceps to place it flat on a clean glass slide.
要观察洋葱表皮细胞，先从洋葱鳞片叶内侧撕下一小片非常薄的表皮。用镊子将其平铺在干净的载玻片上。
Add one drop of water to the tissue, then add one drop of iodine solution. Iodine stains the nucleus and cell wall, making them easier to see.
在组织上加一滴清水，然后再加一滴碘液。碘液可以将细胞核和细胞壁染色，使它们更容易被观察到。
Lower a coverslip slowly at an angle of about 45 degrees, using a mounted needle or forceps. This technique helps to push out air and reduces the number of air bubbles that can obstruct your view.
用解剖针或镊子将盖玻片以约45度的角度缓慢放下。这一技巧有助于排出空气，减少阻挡视野的气泡。
Blot any excess liquid with a paper towel and place the slide on the microscope stage. Start with low power to locate the cells before increasing magnification.
用纸巾吸去多余的液体，然后将玻片放在载物台上。先用低倍镜找到细胞，再切换到更高的倍数进行观察。
4. Testing for Starch with Iodine Solution | 碘液测试淀粉
The iodine test for starch is one of the most common practicals in Year 7. Iodine solution is normally yellow-brown. In the presence of starch, it changes to a blue-black colour.
碘液测试淀粉是七年级最常见的实验之一。碘液原本是黄棕色的，遇到淀粉时会变成蓝黑色。
Place a small sample of the food to be tested on a white spotting tile. Use a dropper to add two or three drops of iodine solution directly onto the food. Observe the colour change carefully.
将少量待测食物样品放在白色滴试板上。用滴管直接滴加两到三滴碘液在食物上，仔细观察颜色变化。
If testing a leaf for starch, the leaf must first be boiled, then heated in ethanol and rinsed in warm water before adding iodine. This removes chlorophyll so the colour change is visible.
如果检测叶片中的淀粉，必须先将叶片煮沸，再在乙醇中加热，然后用温水漂洗，最后才能滴加碘液。这一步是为了脱去叶绿素，使颜色变化清晰可见。
Remember that iodine solution can be an irritant. Wear safety goggles and wash your hands after the experiment.
请记住碘液可能具有刺激性。操作时佩戴护目镜，实验结束后洗手。
5. Testing for Reducing Sugars (Benedict's Test) | 班氏试剂测试还原糖
Benedict' from blue → green → yellow → orange → brick-red, depending on the concentration of sugar.
班氏试剂是一种蓝色液体，与葡萄糖等还原糖一同加热时会变色。颜色变化次序为蓝→绿→黄→橙→砖红色，取决于糖的浓度。
Mix equal volumes of the food solution and Benedict's solution in a test tube. Place the tube in a beaker of hot water (a water bath) and heat for about five minutes. Never point the mouth of the test tube at anyone.
将等体积的食物溶液和班氏试剂在试管中混合。将试管放入盛有热水的烧杯(水浴)中加热约五分钟。试管口千万不要对着任何人。
For a fair comparison, the water bath temperature and the volume of Benedict's solution must be kept the same for all samples. These are control variables.
为了公平比较，所有样品的水浴温度和班氏试剂体积必须保持相同。这些属于控制变量。
6. Measuring Temperature and Using a Thermometer | 测量温度和使用温度计
Always read the thermometer at eye level to avoid parallax error. The bulb of the thermometer should be fully immersed in the substance you are measuring, but it must not touch the bottom or sides of the container.
始终在视平线高度读取温度计，以避免视差错误。温度计的球部应完全浸入待测物质中，但绝对不能碰到容器底部或侧壁。
In biological experiments, temperature is often the independent variable (the one you change) or a control variable that must be kept constant. A water bath is often used to maintain a steady temperature.
在生物实验中，温度常常作为自变量（你改变的那个变量）或需要保持不变的控制变量。通常使用水浴来维持稳定的温度。
Record temperatures in degrees Celsius (°C) and allow the reading to stabilise before writing it down. Stirring gently helps the heat spread evenly.
以摄氏度(°C)为单位记录温度，并等待读数稳定后再记录。轻轻搅拌有助于热量均匀分布。
7. Identifying Variables | 识别变量
The independent variable is the factor that you deliberately change or investigate. For example, in a starch test with different foods, the type of food is the independent variable.
自变量是你故意改变或研究的那个因素。例如，在检测不同食物中的淀粉时，食物种类就是自变量。
The dependent variable is what you measure or observe. In the starch test, the colour change (and whether starch is present) is the dependent variable.
因变量是你测量或观察的量。在淀粉测试中，颜色的变化（以及淀粉是否存在）就是因变量。
Control variables are all the other factors that must be kept the same to make the experiment fair. For a fair test, only the independent variable should be changed. Examples of control variables include the volume of iodine added, the size of the food sample and the room temperature.
控制变量是所有其他必须保持相同的因素，以确保实验公平。为了进行公平测试，只能改变自变量。控制变量的例子包括所加碘液的体积、食物样品的大小以及室温。
8. Recording Results in a Table | 用表格记录结果
Draw your results table using a ruler and a pencil. The first column should list the independent variable, and the second column the dependent variable. Each column heading must include the quantity and the unit, such as 'Temperature (°C)' or 'Colour change'.
用直尺和铅笔绘制你的结果表格。第一列应列出自变量，第二列列出因变量。每一列的标题必须包含物理量和单位，例如“温度(°C)”或“颜色变化”。
Record observations clearly – do not just write 'changed colour'; describe the specific change, for example 'turned blue-black' or 'remained yellow-brown'. Measurements should be given to an appropriate level of precision.
记录观察时要清晰——不要只写“颜色变了”，要描述具体的变化，例如“变成蓝黑色”或“保持黄棕色”。测量值应给出适当的精确度。
9. Drawing Graphs and Charts | 绘制图表
Use a bar chart when your independent variable is categoric (e.g. type of food). The bars must be drawn with equal width and should not touch. Label both axes and give the chart a title.
当自变量是类别变量时（如食物种类），应使用条形图。条形的宽度应相等，且条形之间不能接触。为两条坐标轴添加标签，并为图表写上标题。
Use a line graph when both variables are continuous, such as temperature increase over time. Plot points with a sharp pencil and small crosses, then draw a smooth line of best fit. The x-axis usually carries the independent variable, and the y-axis the dependent variable.
当两个变量都是连续变量时（如温度随时间的变化），应使用线形图。用尖铅笔以小十字标绘数据点，然后画一条平滑的最佳拟合线。横轴通常表示自变量，纵轴表示因变量。
Choose a sensible scale that uses at least half of the graph paper. Never forget to write the units next to the axis labels, and ensure the scale increases in equal steps.
选择合适的标度，至少要能利用一半的方格纸面积。不要忘记在轴标签旁写上单位，并确保标度以相等的间距递增。
10. Writing a Conclusion and Evaluation | 撰写结论与评估
A conclusion should state what you found out and refer back to the data. For instance, 'When iodine solution was added to bread, the colour turned blue-black, indicating starch was present. Apple did not change colour, so no starch was detected.'
结论应说明你发现了什么，并引回到数据上。例如，“当碘液滴加在面包上时，颜色变为蓝黑色，说明有淀粉存在。苹果没有变色，因此未检测到淀粉。”
The evaluation looks at how trustworthy your results are. Identify any anomalous results that do not fit the pattern, and suggest reasons for them. Think about whether you had enough repeats and if the control variables were properly managed.
评估部分考察你的结果有多可信。找出任何不符合规律的异常结果，并推测原因。想一想你是否有足够的重复实验，以及控制变量是否得到了适当的管理。
Suggest practical improvements, such as using a water bath instead of direct heating, measuring volumes more accurately with a syringe, or using a fresh sample to avoid contamination.
提出实际的改进建议，例如用水浴代替直接加热、用注射器更精确地测量体积，或者使用新鲜样品以避免污染。
11. Investigating Photosynthesis – Testing a Leaf for Starch | 探究光合作用——检验叶片中的淀粉
This classic experiment shows that light is needed for photosynthesis. A plant is kept in the dark for 24–48 hours to destarch the leaves. A leaf is then partially covered with aluminium foil, and the plant is placed in bright light for several hours.
这个经典实验证明光合作用需要光。先将植物放在黑暗中24–48小时，使叶片中的淀粉耗尽。然后用铝箔将一片叶子部分遮住，再把植物放在强光下照射数小时。
After the light exposure, remove the leaf and immediately place it in boiling water for about one minute to soften the leaf and kill the tissue. Then place the leaf into a boiling tube of ethanol and stand the tube in hot water. The ethanol will boil and extract the chlorophyll – this step must be done well away from any naked flame because ethanol is highly flammable.
光照结束后，摘下叶片，立即将其放入沸水中煮约一分钟，以软化叶片并杀死组织。然后把叶子放进盛有乙醇的沸腾管中，并将管置于热水中加热。沸腾的乙醇会脱去叶绿素——这一步必须远离明火，因为乙醇高度易燃。
Once the leaf turns white, rinse it in warm water to soften it. Spread the leaf on a white tile and add a few drops of iodine solution. The areas exposed to light will turn blue-black, while the covered area will remain yellow-brown. This proves that light is essential for starch production.
当叶片变成白色后，用温水漂洗使其软化。将叶片平铺在白色滴试板上，滴加几滴碘液。暴露在光下的部分会变成蓝黑色，而被遮盖的部分则保持黄棕色。这证明了光是淀粉生成必不可少的条件。
12. Investigating Respiration – Carbon Dioxide Production | 探究呼吸作用——二氧化碳的产生
Living organisms release carbon dioxide (CO₂) during respiration. One simple way to detect CO₂ is to bubble the gas through limewater (calcium hydroxide solution). If CO₂ is present, the clear limewater turns milky or cloudy.
生物在呼吸作用中会释放二氧化碳（CO₂）。检测二氧化碳的一个简单方法是让气体通过石灰水（氢氧化钙溶液）。如果存在二氧化碳，澄清的石灰水就会变浑浊或呈乳白色。
A safe Year 7 investigation uses germinating seeds or yeast. For example, set up a flask containing warm water, sugar and yeast. Connect the flask to a test tube of limewater using a delivery tube. Keep the apparatus in a warm place and observe the limewater after 20–30 minutes.
七年级可以采用安全的探究方式，使用萌发的种子或酵母。例如，在一个烧瓶中加入温水、糖和酵母，用导管将烧瓶连接到装有石灰水的试管。将整个装置放在温暖处，20–30分钟后观察石灰水的变化。
As a control, set up an identical experiment with boiled peas or dead yeast that have been cooled. The control limewater should remain clear, confirming that living organisms are responsible for the carbon dioxide production.
作为对照，可以设置一个完全相同的实验，但使用煮熟并冷却的豌豆或灭活的酵母。对照组的石灰水应保持澄清，从而证实是活生物体产生了二氧化碳。
Published by TutorHao | Biology Revision Series | aleveler.com
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