📚 IB Science: Laboratory Practical Guide | IB科学：实验操作指南
Mastering laboratory skills is essential for success in IB science subjects—Biology, Chemistry, and Physics. The Internal Assessment (IA) requires you to design and conduct your own experiment, collect and process data, and evaluate your findings. This guide covers every step from planning to report writing, helping you meet the assessment criteria and achieve top marks.
掌握实验技能对于IB科学（生物、化学、物理）的成功至关重要。内部评估（IA）要求你设计并实施自己的实验，收集和处理数据，并评估你的发现。本指南涵盖了从计划到撰写报告的每一步，帮助你满足评估标准并获得高分。
1. Understanding the IA Criteria | 理解内部评估标准
The IA is assessed against five criteria: Personal Engagement, Exploration, Analysis, Evaluation, and Communication. Personal Engagement rewards your initiative and originality; Exploration evaluates the scientific context and methodology; Analysis looks at data processing, uncertainties, and presentation; Evaluation judges your conclusion and weaknesses; Communication focuses on structure, clarity, and use of terminology. Always keep these in mind when designing and reporting your experiment.
IA 根据五个标准进行评估：个人参与、探索、分析、评估和交流。个人参与奖励你的主动性和原创性；探索评估科学背景和方法论；分析关注数据处理、不确定度和呈现方式；评估判断你的结论和实验弱点；交流聚焦于结构、清晰度和术语使用。在设计和报告实验时，时刻牢记这些标准。
2. Choosing a Research Question | 选择研究问题
Your research question must be focused, testable, and enable collection of quantitative data. A weak question: ‘How does temperature affect seed germination?’ A strong one: ‘How does exposure to temperatures of 10°C, 20°C, 30°C, and 40°C for 48 hours affect the germination rate of mung beans, measured as radicle emergence percentage over 5 days?’ This includes clear independent (temperature) and dependent (germination rate) variables, measurable outcomes, and a defined time frame.
你的研究问题必须具体、可测试，并能够收集定量数据。一个薄弱的问题：“温度如何影响种子发芽？” 一个有力的提问：“在10°C、20°C、30°C和40°C下暴露48小时如何影响绿豆的发芽率，以5天内胚根萌发百分比来测量？” 这包括明确的自变量（温度）和因变量（发芽率）、可测量的结果以及确定的时间范围。
3. Variables and Controls | 变量与控制变量
Identify and list independent, dependent, and controlled variables explicitly. The independent variable is what you change; the dependent variable is what you measure. Control variables are kept constant to ensure a fair test. For a pendulum experiment investigating length vs. period, control variables include mass of bob, amplitude, and air currents. For each, explain why it must be controlled and how you will manage it.
明确识别并列出自变量、因变量和控制变量。自变量是你改变的变量；因变量是你测量的变量。控制变量保持恒定以确保公平测试。在摆长与周期的实验中，控制变量包括摆锤质量、振幅和气流。对于每个变量，解释为什么必须控制它以及你将如何管理它。
4. Experimental Design | 实验设计
Design a method that yields at least five different values of the independent variable and allows for repeated trials (minimum three) for each to enhance reliability. Draw a clear labelled diagram of your apparatus. Describe the steps sequentially, using precise quantities and durations. For example, in a rate-of-reaction experiment, specify volumes, concentrations, and temperatures. Remember to include how you will reduce random errors through repetition and systematic errors through calibration or procedural checks.
设计一个方法，至少提供五个不同的自变量值，并对每个值进行至少三次重复试验以提高可靠性。绘制清晰的装置标注图。按顺序描述步骤，使用精确的数量和时间。例如，在反应速率实验中，指定体积、浓度和温度。记住要说明如何通过重复试验减少随机误差，以及如何通过校准或程序检查减少系统误差。
5. Collecting Data | 数据收集
Record raw data in a clear table with a descriptive title, column headings including units, and consistent significant figures. Use measuring instruments to their full precision and note any deviations. For instance, when measuring length with a ruler marked in mm, record to the nearest 0.5 mm to reflect the instrument’s uncertainty. Organise qualitative observations alongside quantitative data, which can later support your evaluation.
在清晰的表格中记录原始数据，表格要有描述性标题、包含单位的列标题以及一致的有效数字。使用测量仪器时充分利用其精度，并记录任何偏差。例如，当使用毫米刻度的尺子测量长度时，记录到最接近的0.5 mm以反映仪器的测量不确定度。将定性观察与定量数据一并整理，这些观察随后可支持你的评估。
6. Recording Uncertainties | 记录不确定度
All measurements involve uncertainty. State the absolute uncertainty for each instrument. For a digital balance displaying 0.01 g, the uncertainty is typically ±0.01 g. For an analogue thermometer with 1°C divisions, the reading uncertainty is ±0.5°C. When you calculate derived quantities, propagate uncertainties. For addition or subtraction, add absolute uncertainties; for multiplication or division, add percentage uncertainties. Always demonstrate these steps in your analysis.
所有测量都包含不确定度。说明每个仪器的绝对不确定度。对于显示0.01 g的电子天平，不确定度通常为±0.01 g。对于刻度为1°C的水银温度计，读数不确定度为±0.5°C。当你计算导出量时，需进行不确定度传递。对于加减运算，相加绝对不确定度；对于乘除运算，相加百分比不确定度。在你的分析中务必展示这些步骤。
Absolute uncertainty from a scale = ± ½ smallest division
标尺的绝对不确定度 = ± ½ 最小分度
7. Data Processing & Graphs | 数据处理与图表
Process raw data to reveal trends: calculate averages, rates, or other derived quantities. Present these in a second table clearly labelled as processed data. Use appropriate graphs; scatter plots with a line of best fit are common. Label axes with variable name and unit, use a sensible scale, plot points accurately, and show uncertainty bars where significant. If the relationship appears linear, calculate the gradient and intercept, discussing their physical meaning.
处理原始数据以揭示趋势：计算平均值、速率或其他导出量。将这些结果呈现在第二个表格中，并清楚标记为处理后数据。使用恰当的图表；散点图及最佳拟合线是常见的。用变量名称和单位标记坐标轴，使用合理的比例，准确描点，并在显著的地方显示误差棒。如果关系呈现线性，计算斜率和截距，并讨论其物理意义。
8. Error Analysis | 误差分析
Distinguish between random and systematic errors. Random errors reduce precision and are minimised by taking repeats; systematic errors reduce accuracy and can be caused by faulty equipment or poor technique. For your IA, identify potential sources of both types, explain their impact on results, and suggest realistic improvements—not just ‘use better equipment’. For example, if heat loss was a systematic error in a calorimetry experiment, propose using an insulating lid or taking temperature readings at shorter intervals.
区分随机误差和系统误差。随机误差降低精密度，可通过重复试验最小化；系统误差降低准确度，可能由设备故障或不当操作引起。在你的IA中，识别可能存在的两类误差源，解释它们对结果的影响，并提出切实可行的改进措施——而不仅仅是“使用更好的设备”。例如，如果在量热实验中热量损失是一个系统误差，可以建议使用隔热盖或更短的时间间隔记录温度。
9. Safety Considerations | 安全考量
Risk assessment is mandatory. List the hazards associated with your materials and procedures, assess the risk level, and describe the precautions taken. For example, using a Bunsen burner: hazard—fire, risk—burns, precaution—tie back long hair, use a heat-proof mat, keep flammable substances away. Refer to appropriate safety data sheets, wear personal protective equipment (goggles, lab coat), and note disposal methods for chemicals. Ethical considerations are equally important in biological experiments involving living organisms.
风险评估是强制性的。列出与你的材料和步骤相关的危险源，评估风险等级，并描述采取的预防措施。例如，使用本生灯：危险源——火，风险——烧伤，预防措施——束起长发、使用隔热垫、远离易燃物。参考适当的安全数据表，穿戴个人防护装备（护目镜、实验服），并注明化学品的处置方法。在涉及活体生物的实验中，道德考量同样重要。
10. Writing the Lab Report | 撰写实验报告
Structure your report logically: Introduction (context, research question, hypothesis), Methodology (apparatus, procedure, variables), Results (raw data, processed data, graphs), Analysis (uncertainty propagation, error discussion), Conclusion (answer to research question, supported by evidence), Evaluation (weaknesses, improvements, extensions). Use subheadings, clear paragraphing, and correct scientific language. Cite all sources and reflect on how your personal engagement influenced the investigation.
合理构建报告结构：引言（背景、研究问题、假设）、方法（仪器、步骤、变量）、结果（原始数据、处理后数据、图表）、分析（不确定度传递、误差讨论）、结论（回答研究问题，有证据支持）、评估（弱点、改进、延伸）。使用小标题、清晰的分段以及正确的科学语言。引用所有来源，并反思你的个人参与如何影响了调查研究。
11. Common Pitfalls to Avoid | 常见误区
Many students lose marks by failing to record uncertainties, having too few data points, or presenting poorly labelled graphs. Another mistake is ignoring one of the IA criteria—for instance, providing no evidence of personal engagement. Avoid overreaching in your conclusion; state only what the data support. Do not forget to compare your results with literature values and discuss discrepancies honestly. Plagiarism, even of part of a method, is strictly penalised, so write in your own words.
许多学生因未记录不确定度、数据点过少或图表标注不当而丢分。另一个错误是忽略了IA的某个标准——例如，没有提供个人参与的证据。避免在结论中过度推断；只陈述数据支持的内容。不要忘记将你的结果与文献值进行比较，并诚实地讨论差异。抄袭，哪怕是方法的一部分，都会受到严厉惩罚，因此务必用自己的话撰写。
12. Tips for High Marks | 高分技巧
To excel, demonstrate personal engagement by explaining why you chose the topic and how you refined your method. Show thorough understanding of uncertainty by calculating percentage uncertainties and discussing their impact. Use a digital tool like Logger Pro or Excel to generate graphs with error bars and trendline equations. In the evaluation, go beyond generic statements—suggest specific, realistic investigations for further study. Finally, proofread for clarity and precision; a well-communicated report leaves a lasting positive impression on the examiner.
要获得高分，请通过解释你为什么选择该主题以及如何改进方法来展示个人参与。通过计算百分比不确定度并讨论其影响来显示你对不确定度的深刻理解。使用如Logger Pro或Excel等数字工具生成带有误差棒和趋势线方程的图表。在评估中，不要停留在泛泛的陈述——提出具体、现实的后续研究建议。最后，仔细校对以确保清晰和准确；一份表达良好的报告会给考官留下持久的正面印象。
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