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Edexcel Combined Science 220: Core Practical Skills and Data Analysis | 爱德思综合科学 220：核心实验技能与数据分析

2026-08-29 16:51 · 本文部分内容由AI辅助创作

📚 Edexcel Combined Science 220: Core Practical Skills and Data Analysis | 爱德思综合科学 220：核心实验技能与数据分析

In Edexcel Combined Science, core practicals are not just demonstrations; they test your ability to plan, measure, process and evaluate scientific evidence. This article focuses on the skills assessed across Biology, Chemistry and Physics, using the specification code 220 as a reference for combined science practical work.

在爱德思综合科学中，核心实验不仅仅是演示，而是考查你计划、测量、处理与评价科学证据的能力。本文聚焦于生物、化学和物理共同评估的实验技能，以综合科学 220 中的核心实验内容为参考。

1. Variables and Hypotheses | 变量与假设

A hypothesis must be a clear, testable statement linking an independent variable (IV) to a dependent variable (DV). For combined science practicals, state how changing the IV is expected to change the DV, and keep all control variables constant.

假设必须是清晰、可检验的陈述，将自变量（IV）与因变量（DV）联系起来。在综合科学实验中，要说明改变自变量预期如何改变因变量，并保持所有控制变量不变。

Variable type 变量类型Definition 定义Example: enzyme pH practical 示例：酶 pH 实验
Independent 自变量The variable you change 你改变的变量pH of buffer 缓冲液 pH
Dependent 因变量The variable you measure 你测量的变量Time for starch to disappear 淀粉消失的时间
Control 控制变量Variables kept constant 保持不变的变量Temperature, enzyme concentration 温度、酶浓度

If a control variable is not managed, the experiment becomes invalid because you cannot attribute the change in the dependent variable only to the independent variable.

如果没有控制变量得到管理，实验就会失效，因为你不能将因变量的变化仅归因于自变量。

2. Apparatus and Measurement | 仪器与测量

Choose apparatus with an appropriate resolution and range. For example, a 25 cm³ measuring cylinder has a resolution of 1 cm³, while a 50 cm³ burette has a resolution of 0.1 cm³; use the burette for titration.

选择具有合适分辨率和量程的仪器。例如，25 cm³ 量筒的分辨率为 1 cm³，而 50 cm³ 滴定管的分辨率为 0.1 cm³；滴定时应使用滴定管。

Record all measurements to the full precision shown by the instrument, including trailing zeros, to avoid losing resolution. For example, write 12.0 cm³ instead of 12 cm³ if the instrument measures to 0.1 cm³.

记录所有测量值时要保留仪器显示的全部精度，包括末尾的零，以免丢失分辨率。例如，如果仪器能测到 0.1 cm³，就应记录为 12.0 cm³，而不是 12 cm³。

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3. Accuracy, Precision and Uncertainty | 准确度、精密度与不确定度

Accuracy describes how close a result is to the true value, while precision describes how close repeated measurements are to each other. A systematic error reduces accuracy; random error reduces precision.

准确度描述结果与真实值的接近程度，精密度描述重复测量值之间的接近程度。系统误差降低准确度，随机误差降低精密度。

For a single measurement, absolute uncertainty is usually half the smallest scale division. Percentage uncertainty is calculated as:

对于单次测量，绝对不确定度通常取最小分度值的一半。百分不确定度的计算公式为：

percentage uncertainty = (absolute uncertainty ÷ measured value) × 100%

C, the absolute uncertainty is ±0.5 °C and the percentage uncertainty is ±(0.5 ÷ 25) × 100% = ±2%.

例如，如果温度计的最小分度为 1 °C，读数为 25 °C，则绝对不确定度为 ±0.5 °C，百分不确定度为 ±(0.5 ÷ 25) × 100% = ±2%。

4. Recording Data and Tables | 记录数据与表格

Use a ruled table with clear headings, units and a column for the mean. Circle anomalies only after repeating, and do not include them in the mean.

使用带有清晰标题、单位和平均值栏的表格。只有在重复实验后才可以圈出异常值，且计算平均值时不包含异常值。