📚 IB CIE Science: Laboratory Practical Guide | IB CIE 科学：实验操作指南
Mastering laboratory skills is essential for success in IB and CIE science courses. This guide provides a comprehensive framework for designing, conducting, and evaluating experiments, covering safety, variables, measurement, data handling, graphing, and error analysis. A methodical approach not only ensures reliable results but also deepens conceptual understanding and prepares you for internal assessments and practical examinations.
掌握实验技能是学好 IB 和 CIE 科学课程的关键。本指南为实验的设计、操作和评估提供了全面的框架，涵盖安全、变量、测量、数据处理、图表绘制和误差分析。有条不紊的方法不仅能确保结果可靠，还能加深对概念的理解，并为内部评估和实验考试做好准备。
1. Safety First in the Laboratory | 实验室安全第一
Always wear appropriate personal protective equipment, including safety goggles, lab coat, and closed-toe shoes. Tie back long hair and avoid loose clothing to prevent accidents with open flames or rotating equipment. Familiarise yourself with the location of the eyewash station, safety shower, fire extinguisher, and first-aid kit before starting any practical work.
始终穿戴适当的个人防护装备，包括护目镜、实验服和包头鞋。将长发束起，避免穿着宽松衣物，以防被明火或旋转设备卷入。开始任何实验操作前，务必了解洗眼器、紧急淋浴器、灭火器和急救箱的位置。
Never eat, drink, or taste chemicals in the lab. Read all reagent labels carefully and handle concentrated acids and alkalis inside a fume hood. When diluting strong acids, always add acid to water, not the opposite, to avoid violent exothermic splashing. Dispose of chemical waste and sharps in designated containers following your school’s safety protocols.
切勿在实验室饮食或品尝化学品。仔细阅读所有试剂标签，并在通风橱内处理浓酸和浓碱。稀释强酸时，务必将酸缓慢加入水中，切勿反向操作，以避免剧烈放热导致飞溅。按照学校的安全规程，将化学废液和尖锐物品放入指定容器中处理。
2. Understanding Variables and Controls | 理解变量与对照
The independent variable is the factor you deliberately change or manipulate during the experiment, such as the concentration of a reactant or the length of a wire. It is plotted on the x-axis of a graph. The dependent variable is what you measure or observe as a response; it changes as a result of the independent variable and is plotted on the y-axis.
自变量是你在实验中刻意改变或操纵的因素，例如反应物浓度或导线长度，它在图中绘制于 x 轴。因变量是你测量或观察到的响应结果；它随自变量的改变而变化，在图中绘制于 y 轴。
Control variables are all other factors that must be kept constant to ensure a fair test. Examples include temperature, pressure, volume, or the same batch of enzyme solution. A control group or baseline measurement should be included where possible, providing a reference point in which the independent variable is absent or set at a standard value.
控制变量是所有必须保持恒定的其他因素，以确保公平测试。例如温度、压强、体积或同一批次的酶溶液。在可能的情况下，应设置对照组或基线测量，提供自变量不存在或设定为标准数值的参照点。
3. Writing a Clear Aim and Hypothesis | 撰写清晰的目的与假设
The aim states succinctly what the experiment intends to investigate, often beginning with “To investigate the effect of [independent variable] on [dependent variable]”. The hypothesis is a testable prediction based on scientific theory, usually framed as “If… then… because…”. It should include a directional statement and a justification rooted in accepted principles.
实验目的简洁地陈述实验要探究的内容，通常以“探究[自变量]对[因变量]的影响”开头。假设是基于科学理论的可检验预测，通常表述为“如果……那么……因为……”。它应包含方向性陈述以及基于公认原理的合理解释。
A good hypothesis for a chemistry rates experiment could be: If the concentration of hydrochloric acid increases, then the rate of reaction with magnesium will increase, because a higher concentration means more reactant particles per unit volume, leading to more frequent successful collisions.
化学速率实验的一个好假设可以是：如果盐酸浓度增加，那么镁与盐酸的反应速率会加快，因为浓度越高，单位体积内的反应粒子越多，导致成功碰撞的频率更高。
4. Selecting Appropriate Apparatus and Materials | 选择适当的仪器与材料
Choose apparatus that offers the necessary precision and range for your measurements. For volumes, graduated cylinders, volumetric pipettes, and burettes provide increasing levels of accuracy. A standard thermometer measures to ±0.5 °C, while a digital temperature probe may record to ±0.1 °C. Always record the resolution and uncertainty of each instrument.
选择能提供所需精度和量程的仪器。对于体积测量，量筒、移液管和滴定管的精度依次递增。普通温度计的测量精度为 ±0.5 °C，而数字温度探头可达到 ±0.1 °C。务必记录每种仪器的分辨率和不确定度。
In physics, using a micrometer screw gauge ( ±0.01 mm) is preferable to a vernier caliper ( ±0.1 mm) for measuring the diameter of a thin wire. In biology, a colorimeter yields more objective data than a colour chart when quantifying pigment intensity. List all materials with their sizes, concentrations, and quantities to ensure reproducibility.
在物理中，测量细金属丝的直径时，使用螺旋测微计（±0.01 mm）比游标卡尺（±0.1 mm）更合适。在生物中，量化色素强度时，比色计比色卡能提供更客观的数据。列出所有材料及其规格、浓度和数量，以确保实验可重复。
5. Designing a Rigorous Method | 设计严谨的实验步骤
Write the procedure in clear, numbered steps, using the imperative mood. Include precise quantities, timings, and instrument settings. Specify how control variables will be maintained and how the independent variable will be manipulated across a suitable range. A minimum of five different values of the independent variable is usually recommended to establish a reliable trend.
用清晰的编号步骤书写实验步骤，使用祈使语气。包含精确的数量、时间和仪器设置。说明如何维持控制变量，以及如何在适当的范围内操控自变量。通常建议至少使用五个不同的自变量值，以建立可靠的变化趋势。
Include replicates: each measurement should be repeated at least twice under identical conditions, yielding three sets of data for averaging. This reduces the impact of random errors. Mention any techniques to minimise systematic errors, such as zeroing a balance, avoiding parallax error by reading the meniscus at eye level, and pre-heating or pre-cooling apparatus.
设置重复实验：每次测量至少应在相同条件下重复两次，获得三组数据以计算平均值，这能减少随机误差的影响。提及任何能减少系统误差的技巧，例如调零天平、在视线水平处读取弯月面以避免视差，以及对仪器进行预热或预冷。
6. Collecting and Recording Raw Data | 收集与记录原始数据
Design a data table before starting the experiment. Columns should be headed by the name and unit of the quantity, separated by a slash, e.g. “Time / s”. Enter all values to the same number of decimal places consistent with the instrument’s precision. Never alter raw data; if a result appears anomalous, flag it with a note but keep the entry.
实验开始前设计好数据表格。表头应包含量的名称和单位，用斜线隔开，例如“时间 / s”。所有数值应保留与仪器精度一致的小数位数。切勿修改原始数据；若某个结果看似异常，标注说明但保留该数值。
Qualitative observations, such as colour changes, gas evolution, precipitate formation, or temperature fluctuations, are equally valuable. Record them in a separate column or logbook promptly. Use precise, objective language — for example, “colourless solution turned pale pink after 12.50 cm³ of titrant added”, rather than vague descriptions.
定性观察同样重要，如颜色变化、气体释放、沉淀生成或温度波动，应及时记录在单独的栏或记录本中。使用精确、客观的语言，例如“加入 12.50 cm³ 滴定剂后，无色溶液变为浅粉色”，而非模糊的描述。
7. Data Processing and Calculations | 数据处理与计算
Present processed data in a second table, showing calculated values and their units. For rates, use Change in quantity / Time taken. Show at least one sample calculation for each type of derived quantity. State the formula used, show substitution, and give the final answer to the appropriate number of significant figures (usually matching the least precise measurement).
在第二个表格中呈现处理后的数据，展示计算值及其单位。对于速率，使用 变化量 / 所需时间。每种推导量至少展示一个计算示例。写出所用公式，代入数值，并将最终答案保留至合适的有效数字（通常与最不精确的测量值一致）。
When calculating averages, omit clear anomalous values but justify their exclusion in the evaluation. Use the absolute uncertainty of a measurement to propagate uncertainties through additions, subtractions, multiplications, and divisions. For a burette reading of 23.50 ± 0.05 cm³, the percentage uncertainty is (0.05 / 23.50) × 100% ≈ 0.21%.
计算平均值时，剔除明显异常值，但在评估中说明剔除的理由。利用测量的绝对不确定度，通过加减乘除运算传递不确定度。例如，滴定管读数为 23.50 ± 0.05 cm³，其百分比不确定度为 (0.05 / 23.50) × 100% ≈ 0.21%。
8. Graphing and Presenting Trends | 绘图与趋势呈现
Plot graphs on appropriately scaled axes, with the independent variable on the x-axis and the dependent on the y-axis. Choose a scale that makes the plotted points occupy more than half the graph paper in both directions. Label axes with quantity and unit, and use a sharp pencil to mark points with small crosses or circled dots. Add a descriptive title.
在比例适当的坐标轴上绘图，自变量在 x 轴，因变量在 y 轴。选择能使数据点占据网格纸一半以上面积的尺度。用数量和单位标注坐标轴，用削尖的铅笔以小十字或圆圈标记数据点。添加能说明图意的标题。
Plot a best-fit line or curve that reveals the underlying relationship. Do not force the line through the origin unless justified by theory. If the data is linear, calculate the gradient using a large triangle that spans at least half the line. The gradient and y-intercept should be expressed with appropriate units and interpreted in physical terms.
绘制最佳拟合线或曲线以揭示内在关系。除非有理论依据，否则不要强行让直线穿过原点。如果数据呈线性，使用覆盖至少一半直线的大三角形计算斜率。斜率和 y 截距应带有适当的单位，并从物理角度进行解释。
9. Evaluating Errors and Uncertainties | 评估误差与不确定度
Distinguish between random and systematic errors. Random errors cause readings to be spread about the true value and can be reduced by taking more replicates and averaging. Systematic errors shift all readings in one direction due to faulty equipment or flawed design; they are addressed by calibration or improved technique.
区分随机误差和系统误差。随机误差导致读数分散在真值周围，可通过增加重复次数和求平均来减少。系统误差因设备故障或设计缺陷使所有读数朝一个方向偏移，可通过校准或改进技术来解决。
Uncertainty in a single measurement is often taken as half the smallest scale division. For digital instruments, it is the smallest displayed digit. When comparing repeats, calculate the range. If the range exceeds the instrumental uncertainty, use the range as a more realistic estimate of the random uncertainty for that set of data.
单次测量的不确定度通常取最小刻度的一半。对于数字仪器，则为最后一位显示数字。比较重复测量值时，计算极差。如果极差大于仪器不确定度，则将极差作为该组数据随机不确定度更实际的估计值。
10. Drawing Valid Conclusions | 得出有效结论
State whether the data supports or refutes the hypothesis, citing specific evidence from the graph or trends. Avoid overstating findings; instead use phrasing such as “within the limits of this experiment, there is a direct proportional relationship between…”. Mention the mathematical relationship if one is identified, and give the equation with uncertainties for the constants.
说明数据支持还是否定假设，并引用图表或趋势中的具体证据。避免夸大发现，而应使用诸如“在本实验的限度内，……之间存在正比关系”的表述。如果识别出数学关系，请给出关系式并注明常数值的不确定度。
Compare your results with accepted literature values, if available, by calculating the percentage error: |Experimental value – Accepted value| / Accepted value × 100%. Discuss possible causes for any discrepancies, linking them back to specific errors identified in the evaluation. Suggest targeted improvements, not vague statements like “be more careful”.
如有公认文献值，计算百分误差： |实验值 – 公认值| / 公认值 × 100%，将结果与之比较。讨论任何差异的可能原因，并联系到评估中识别出的具体误差。提出有针对性的改进建议，而不是“再仔细一点”这样含糊的表述。
11. Reflecting on Improvements and Extensions | 反思改进与延伸
Propose at least two concrete modifications to the method that would enhance accuracy or reliability. For instance, using a thermostatically controlled water bath instead of a beaker of hot water to stabilise temperature, or replacing a stopwatch with light gates and a data logger to eliminate human reaction time.
提出至少两项能提高准确度或可靠性的具体方法改进。例如，使用恒温水浴锅代替烧杯热水以稳定温度，或用光门和数据记录器替代秒表，消除人为反应时间。
Suggest a meaningful extension of the investigation — changing another variable, testing a different material, or applying the same principle to a new context. Explain how this extension would deepen understanding or uncover further patterns, tying it back to the underlying theory.
提出一个有意义的实验延伸——改变另一个变量，测试不同材料，或将同一原理应用于新情境。解释这一延伸如何加深理解或揭示更多规律，并将其与基本原理相联系。
12. Common Core Practicals Overview | 常见核心实验概览
In CIE and IB syllabuses, typical experiments include: investigating the effect of enzyme concentration on reaction rate (biology), determining the formula of hydrated magnesium sulfate by mass loss (chemistry), and measuring the acceleration of free fall using a pendulum or ticker timer (physics). Each demands careful variable control and rigorous data handling.
在 CIE 和 IB 教学大纲中，典型实验包括：探究酶浓度对反应速率的影响（生物），通过质量损失测定水合硫酸镁的化学式（化学），以及使用单摆或打点计时器测量自由落体加速度（物理）。每个实验都要求仔细控制变量并严格处理数据。
Regardless of the discipline, transferable skills such as maintaining a thorough lab journal, recognising the limitations of apparatus, and critically evaluating the validity of a procedure are what examiners value most. Regular practice with past practical papers and mock investigations builds confidence and fluency.
无论学科如何，跨学科的可迁移技能才是考官最看重的，包括保持详尽的实验日志、认识仪器的局限性以及批判性地评估实验步骤的有效性。经常练习往年的实验考试和模拟探究，可以增强信心并提高熟练度。
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