📚 Edexcel Combined Science (098) Investigative Skills and Core Practicals | Edexcel 综合科学 (098) 探究技能与核心实验
Core practical work is the beating heart of Edexcel Combined Science (098), linking theoretical ideas to the evidence you collect in the laboratory. The same investigative skills, from controlling variables to interpreting graphs, are tested repeatedly across biology, chemistry and physics, and they also lay the foundation for A-level scientific thinking.
核心实验是 Edexcel 综合科学 (098) 的核心，它将理论概念与你在实验室中收集的证据联系起来。从控制变量到解读图表，这些探究技能在生物、化学和物理中反复考查，也为 A-level 科学思维打下基础。
1. Understanding Variables and Fair Testing | 理解变量与公平测试
In any Edexcel Combined Science investigation, three types of variable must be identified before you start. The independent variable is the one you deliberately change, the dependent variable is the one you measure, and control variables are all the factors you keep constant to make the test fair.
在任何 Edexcel 综合科学探究中，开始前必须先确定三类变量。自变量是你有意改变的变量，因变量是你测量的变量，控制变量是你为保持测试公平而保持不变的所有因素。
For example, when investigating the effect of temperature on reaction rate, temperature is the independent variable, time or gas volume is the dependent variable, and concentration, volume and surface area are controls.
例如，研究温度对反应速率的影响时，温度是自变量，时间或气体体积是因变量，而浓度、体积和表面积是控制变量。
A common mistake is confusing the control variable with the dependent variable. If a quantity is measured to answer the aim, it is dependent; if it is kept the same to avoid an unfair test, it is a control.
一个常见错误是把控制变量与因变量混淆。如果某个量是为了回答实验目的而测量，它就是因变量；如果保持相同以避免不公平测试，它就是控制变量。
2. Writing a Clear Hypothesis and Prediction | 撰写清晰的假设与预测
A hypothesis must be a clear testable statement that links the independent variable to the dependent variable. It often takes the form ‘As the independent variable increases, the dependent variable increases/decreases because…’ and it must be based on scientific reasoning.
假设必须是清晰可检验的陈述，将自变量与因变量联系起来。它通常采用“随着自变量增加，因变量增加/减少，因为……”的形式，并且必须基于科学原理。
For instance, a valid hypothesis for a rates experiment is: ‘As the concentration of hydrochloric acid increases, the volume of gas produced in 60 seconds increases because there are more frequent collisions between reactant particles.’ Avoid writing a vague statement such as ‘the reaction will change’.
例如，反应速率实验的一个有效假设是：“随着盐酸浓度增大，60 秒内产生的气体体积增大，因为反应物粒子之间的碰撞更频繁。”避免写出“反应会改变”这类模糊陈述。
A prediction is more specific than a hypothesis. It might state the expected pattern in the results, such as ‘doubling the concentration will roughly double the rate’, which can then be tested against the data.
预测比假设更具体。它可以说明结果的预期模式，例如“浓度加倍，速率大约加倍”，然后可以用数据来检验。
3. Planning Experimental Procedures | 设计实验步骤
An effective plan includes a list of apparatus, a step-by-step method, safety considerations, and a strategy for obtaining valid results. You should use equipment that gives sufficient precision for the measurements being made.
有效的实验设计包括仪器清单、分步方法、安全注意事项以及获得有效结果的策略。你应使用对所进行的测量具有足够精度的设备。
Repeated measurements improve reliability by allowing you to calculate a mean and identify outliers. When explaining a choice of range, make sure the intervals of the independent variable are wide enough to show a trend but also include enough values for a smooth pattern.
重复测量可以通过计算平均值和识别异常值来提高可靠性。在解释取值范围的选择时，确保自变量的间隔足够宽以显示趋势，同时包含足够的数值以形成平滑模式。
Safety is always assessable. For example, when heating acids or using electrical circuits, you should state a specific hazard and the matching precaution, such as wearing safety goggles to protect eyes from splashes or switching off the power before making changes.
安全问题始终是考查点。例如，加热酸类或使用电路时，你应说明具体的危险和相应的预防措施，比如佩戴护目镜防止液体飞溅入眼，或在改动前关闭电源。
4. Recording Data: Tables and Units | 记录数据：表格与单位
Data tables must have clear headings that include the quantity and its unit, for example ‘Mass lost (g)’ or ‘Potential difference (V)’. The independent variable is usually placed in the first column and the dependent variable in the next column.
数据表必须有清晰的表头，包含物理量及其单位，例如“质量减少 (g)”或“电势差 (V)”。自变量通常放在第一列，因变量放在下一列。
All readings should be recorded to the resolution of the measuring instrument. A digital balance reading of 0.01 g should be written as 5.20 g, not 5.2 g, to show the precision of the instrument.
所有读数都应按测量仪器的分辨率记录。数字天平读数 0.01 g 应写为 5.20 g，而不是 5.2 g，以体现仪器的精度。
If you calculate a mean, leave anomalies out and explain why they were excluded. The mean should be given to the same number of decimal places as the raw data, or to an appropriate degree of precision.
如果计算平均值，应排除异常值并解释排除原因。平均值应与原始数据保留相同的小数位数，或保留适当精度。
5. Graphing and Interpreting Results | 绘图与解读结果
When plotting graphs, choose scales that use at least half of the graph paper and label each axis with the variable and unit. The independent variable goes on the x-axis and the dependent variable on the y-axis.
绘图时，选择的坐标标度应至少使用坐标纸的一半，并在每个坐标轴上标注变量和单位。自变量放在 x 轴，因变量放在 y 轴。
Plot points with a small sharp cross, draw a line or curve of best fit, and identify any outliers. A line graph is used when there is a continuous relationship, while a bar chart is used for discrete categories.
用小的清晰十字标出数据点，绘制最佳拟合线或曲线，并识别任何异常值。连续关系使用线图，离散类别使用条形图。
Interpreting the graph often involves finding a gradient or pattern. For a straight line, the gradient can be calculated using the formula below. If the line curves, the rate of change is not constant.
解读图表通常涉及求斜率或模式。对于直线，斜率可用下列公式计算。如果曲线弯曲，变化率则不是恒定的。
gradient = Δy ÷ Δx
6. Errors, Accuracy and Precision | 误差、准确度与精密度
Random errors cause readings to spread either side of the true value. They can be reduced by taking repeat measurements and calculating a mean. Systematic errors cause every reading to be shifted in the same direction, often because of an instrument fault or poor technique.
随机误差导致读数在真实值两侧分散。可以通过重复测量并计算平均值来减小。系统误差使每个读数朝同一方向偏移，通常由仪器故障或操作不当引起。
Accuracy describes how close a measurement is to the true value, while precision describes how close repeat readings are to each other. A set of readings can be precise but inaccurate if there is a systematic error.
准确度描述测量值与真实值的接近程度，精密度描述重复读数彼此之间的接近程度。如果存在系统误差，一组读数可能精密度高但不准确。
You can estimate uncertainty by using the half-range method. Calculate the mean of the repeats, find the range, and divide by two. The result should be written with ±, for example 12.4 ± 0.3 s.
你可以使用半范围法估算不确定度。计算重复值的平均值，求出极差，然后除以二。结果应写成 ± 形式，例如 12.4 ± 0.3 s。
uncertainty = range ÷ 2
7. Core Practical: Rates of Reaction | 核心实验：反应速率
In the rates of reaction practical, a common method is to measure the loss in mass of a flask on a balance as a gas escapes, or to collect the gas in a measuring cylinder. The mass or volume is recorded at regular time intervals.
在反应速率实验中，常用方法是在气体逸出时用天平测量烧瓶的质量减少，或用量筒收集气体。每隔固定时间间隔记录质量或体积。
The rate at any point is the gradient of the graph of quantity against time. A steeper gradient means a faster reaction. As the reactants are used up, the rate usually decreases and the curve flattens.
任一点的速率就是数量-时间图线的斜率。斜率越大，反应越快。随着反应物被消耗，速率通常下降，曲线趋于平缓。
rate = ΔV ÷ Δt
Changing concentration or temperature changes particle collision frequency and energy, which can be tested by repeating the experiment under different conditions. Keep the same volume, mass and surface area to ensure a fair comparison.
改变浓度或温度会改变粒子碰撞频率和能量，这可通过在不同条件下重复实验来检验。保持体积、质量和表面积相同以确保公平比较。
8. Core Practical: Electrical Circuits | 核心实验：电路
In electricity core practicals, an ammeter must be placed in series with the component so that the same current passes through it. A voltmeter must be placed in parallel with the component to measure the potential difference across it.
在电学核心实验中，电流表必须与元件串联，使同一电流通过电流表。电压表必须与元件并联，以测量元件两端的电势差。
The resistance of a component can be calculated from current and potential difference. For an ohmic conductor, the resistance is constant if temperature stays constant.
元件的电阻可以从电流和电势差计算。对于欧姆导体，如果温度保持恒定，电阻就是恒定的。
R = V ÷ I
When investigating series and parallel circuits, record your observations and calculate total resistance. In series, total resistance is the sum of individual resistances; in parallel, the total resistance is less than the smallest individual resistance.
在研究串联和并联电路时，记录观察结果并计算总电阻。串联时总电阻等于各电阻之和；并联时总电阻小于其中最小的单个电阻。
9. Core Practical: Microscopy and Biological Drawings | 核心实验：显微镜与生物绘图
To prepare an onion cell slide, peel a thin layer of epidermis, place it flat on a slide, add a drop of iodine to stain the cells, and lower a coverslip at an angle to avoid trapping air bubbles. Use a paper towel to absorb any excess liquid.
制作洋葱细胞装片时，撕取一层薄表皮，平放在载玻片上，滴一滴碘液染色，然后将盖玻片以一定角度放下以避免气泡。用纸巾吸去多余液体。
Start with the lowest-power objective lens, focus using the coarse adjustment knob first, then change to a higher power. The total magnification is the eyepiece lens magnification multiplied by the objective lens magnification.
先用低倍物镜，用粗调焦旋钮对焦，然后换到高倍镜。总放大倍数等于目镜放大倍数乘以物镜放大倍数。
Magnification calculations use the formula below. Always convert image size and actual size to the same units before dividing.
放大倍数计算使用下列公式。计算前一定要将图像尺寸和实际尺寸换算为相同单位。
magnification = image size ÷ actual size
10. Exam Technique and Command Words | 应试技巧与指令词
Command words require different levels of response. ‘State’ needs a short fact, ‘Describe’ needs a sequence of observations or steps, ‘Explain’ needs scientific reasons, and ‘Evaluate’ needs evidence for and against with a final judgement.
指令词要求不同层次的作答。’State’ 需要简短事实，’Describe’ 需要观察或操作的顺序，’Explain’ 需要科学原理，’Evaluate’ 需要支持与反对的证据以及最终判断。
When describing a graph, use the variables in the axes and refer to the trend, for example ‘As temperature increases, the volume of gas increases at a decreasing rate until the reaction stops.’
描述图表时，使用坐标轴中的变量并指出趋势，例如“随着温度升高，气体体积以递减速率增加，直到反应停止”。
Always show your working in calculations by writing the formula, substituting values, and giving the unit. Check that your answer is expressed to a sensible number of significant figures based on the data provided.
在计算中始终展示计算过程，写出公式、代入数值并给出单位。根据所给数据检查答案是否使用了合理有效数字位数。
Published by TutorHao | Combined Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导Cancel reply