📚 Year 7 Edexcel Science: Key Points for Practical Assessments | Year 7 Edexcel 科学：实验/实践考核要点
Practical assessments in Year 7 Edexcel Science are designed to build your core investigative skills. You will be tested on planning valid experiments, collecting accurate data, interpreting results, and evaluating methods. Mastering these points early will give you a strong foundation for all future science courses.
Year 7 Edexcel 科学中的实践考核旨在培养你的核心探究技能。你将接受实验设计、准确数据收集、结果解读以及方法评估的测试。尽早掌握这些要点，将为你今后的所有科学课程打下坚实基础。
1. Safety First in the Lab | 实验室安全第一
Always wear safety goggles to protect your eyes from chemicals and heat.
始终佩戴护目镜，保护眼睛免受化学品和热量的伤害。
Tie back long hair and tuck in loose clothing to prevent accidents with open flames.
将长发扎起并塞好宽松衣物，以防明火引发意外。
Know the location of the fire extinguisher, fire blanket, and emergency shower before starting any experiment.
在开始任何实验前，先了解灭火器、灭火毯和紧急淋浴器的位置。
Never run, eat, or drink in the laboratory; keep your workspace clear and wipe up spills immediately.
切勿在实验室奔跑、进食或饮水；保持工作区域整洁，立即清理溢出物。
When heating substances, always point the mouth of a test tube away from yourself and others.
加热物质时，务必将试管口朝向无人处。
2. Understanding Variables | 理解变量
The independent variable is the factor you deliberately change or choose in the experiment.
自变量是你在实验中故意改变或选择的因素。
The dependent variable is what you measure or observe; its value depends on changes in the independent variable.
因变量是你测量或观察的结果，其数值取决于自变量的变化。
Control variables are all the factors that must be kept the same to ensure a fair test and valid comparison.
控制变量是所有必须保持相同的因素，以确保公平测试和有效比较。
For example, when investigating how temperature affects the rate of dissolving sugar, temperature is the independent variable, the time taken to dissolve is the dependent variable, and the amount of water and sugar are control variables.
例如，在研究温度如何影响蔗糖溶解速率的实验中，温度是自变量，溶解所需时间是因变量，而水的量和蔗糖的量是控制变量。
3. Writing a Method | 编写实验方法
A clear method uses numbered steps that begin with an imperative verb, such as ‘Pour 25 cm³ of water into a beaker’ or ‘Measure 5 g of salt’.
清晰的方法使用以命令动词开头的编号步骤，例如“将25 cm³ 的水倒入烧杯”或“称量5 g 食盐”。
Include precise quantities and the names of specific apparatus, e.g., ‘Use a 50 cm³ measuring cylinder’ rather than just ‘a container’.
写明精确的量和具体仪器名称，例如“使用50 cm³ 量筒”而不仅仅是“一个容器”。
Mention all relevant safety measures, such as ‘Wear heat‑proof gloves when handling hot beakers’ or ‘Place a heat‑proof mat under the Bunsen burner’.
提及所有相关的安全措施，例如“拿取热烧杯时佩戴隔热手套”或“在本生灯下放置隔热垫”。
State how you will make your investigation reliable, for instance, ‘Repeat the experiment three times and calculate a mean’.
阐明如何提高调查的可靠性，例如“重复实验三次并计算平均值”。
4. Using Apparatus Correctly | 正确使用仪器
When reading the volume of a liquid in a measuring cylinder, place your eye level with the bottom of the meniscus to avoid parallax error.
读取量筒内液体体积时，视线应与凹液面底部水平，以避免视差误差。
Use a Bunsen burner with the air hole closed (safety flame, yellow) when not heating; open the air hole (roaring blue flame) for gentle or strong heating.
使用本生灯时，不加热时关闭气孔（黄色安全火焰）；需要加热时打开气孔，形成蓝色强烈火焰。
Place a thermometer in the centre of the liquid without touching the sides or bottom of the container, and wait for the reading to stabilise before recording.
将温度计置于液体中央，不要触碰容器壁或底部，待读数稳定后再记录。
When using a light microscope, start with the lowest power objective lens, use the coarse focusing knob first, and never touch the lens with your fingers.
使用光学显微镜时，先从低倍物镜开始，先用粗准焦螺旋调焦，且切勿用手指触摸镜头。
5. Making Measurements | 进行测量
Record all measurements with the correct unit and to the level of precision the instrument allows, e.g., 2.5 cm on a ruler showing millimetre marks.
记录所有测量值时，要使用正确的单位，并按仪器精度记录，例如在毫米刻度直尺上读作2.5 cm。
Common fundamental measurements include length (mm, cm, m), mass (g, kg), volume (cm³, l), time (s), and temperature (°C).
常见基本测量包括长度（mm, cm, m）、质量（g, kg）、体积（cm³, l）、时间（s）和温度（°C）。
For a digital balance that reads to 0.01 g, always record values like 5.00 g, not 5 g, to show the precision of the instrument.
对于可读至0.01 g的电子天平，一定要记录如5.00 g而不是5 g，以体现仪器精度。
Taking repeat measurements and calculating the mean helps to reduce the effect of random errors and increases reliability.
进行重复测量并计算平均值，有助于减小随机误差的影响，提高可靠性。
6. Recording Data | 记录数据
Draw a results table with clear headings and units before starting your experiment; leave space for repeat readings and an average column.
实验开始前，先绘制带有清晰表头和单位的结果表；为重复读数和平均值列留出空间。
The first column usually lists the values of the independent variable, and subsequent columns are for the dependent variable readings.
第一列通常列出自变量的数值，后续各列用于记录因变量的读数。
For qualitative observations, write descriptive notes such as ‘bubbles formed rapidly’ or ‘blue solution turned colourless’, and note timing if relevant.
对于定性观察，写下描述性记录，如“快速产生气泡”或“蓝色溶液变为无色”，并在相关时记下时间。
Never alter or rub out a reading that looks wrong; mark any anomalous result with a circle, but still keep it, and consider repeating that trial.
切勿更改或擦除看似错误的读数；用圆圈标出任何异常结果，但保留它，并考虑重复该次试验。
7. Drawing Graphs | 绘制图表
Select a line graph when the independent variable is continuous (e.g., temperature, time) and a bar chart when comparing discrete categories.
当自变量为连续量（如温度、时间）时选用折线图，比较不连续类别时选用条形图。
Label the x‑axis with the independent variable and the y‑axis with the dependent variable, both followed by units in parentheses, e.g., ‘Time (s)’.
用自变量标注 x 轴，用因变量标注 y 轴，两者后均用括号注明单位，例如“时间 (s)”。
Choose a scale that makes your plotted points spread over more than half the grid; use small crosses or circled dots, and never join the dots with a ruler for a curve.
选择使描点占据网格一半以上的刻度；用小叉号或带圈的点标绘，曲线拟合切勿用直尺硬连端点。
Draw a line of best fit: a straight line with a ruler if the points suggest a linear trend, or a smooth freehand curve if they show a curved pattern.
画出最佳拟合线：若散点呈线性趋势，用直尺画直线；若呈曲线趋势，用手绘平滑曲线。
When describing a trend, say something like ‘As temperature increases, the time to dissolve decreases steadily’.
描述趋势时，要说“随着温度升高，溶解时间稳步缩短”之类的句式。
8. Drawing Conclusions | 得出结论
A conclusion should link directly back to the investigation question and state whether the data support or do not support the original prediction.
结论应直接回扣探究问题，并说明数据是否支持最初的预测。
Support your conclusion with actual figures or clear trends, for example: ‘At 30°C the reaction took 48 s, while at 50°C it took only 22 s, showing that higher temperature increases the rate.’
用实际数据或明确趋势支持你的结论，例如：“30°C 时反应耗时48秒，而50°C 时仅需22秒，说明高温加快了反应速率。”
Avoid words such as ‘prove’ or ‘correct’; in science we say ‘the results support the hypothesis’ because further tests might give different outcomes.
避免使用“证明”或“正确”等词语；在科学中我们说“结果支持假设”，因为后续实验可能得出不同结果。
If your graph shows no clear pattern, admit that and suggest collecting more data or adjusting the range of the independent variable.
如果图表没有明显趋势，应如实指出，并建议收集更多数据或调整自变量范围。
9. Evaluating Experiments | 评估实验
Assess reliability by examining whether repeat readings are close together; closely grouped results indicate high precision.
通过检查重复测量值是否相近来评估可靠性；结果聚集紧密表明精密度高。
Check validity by asking: ‘Was this a fair test? Were all control variables truly constant? Did I measure the right thing?’
通过自问“这是公平测试吗？所有控制变量真的恒定吗？我测量的是正确的指标吗？”来检验有效性。
Identify common sources of error, such as human reaction time with a stopwatch, heat loss to the air, or difficulty judging a colour change endpoint.
识别常见误差来源，例如按秒表的人为反应时间、向空气的热损失，或判断颜色变化终点的困难。
Suggest specific, practical improvements – not just ‘do it more carefully’. For instance, ‘Use a light sensor and data logger to measure colour change instead of relying on eye judgement.’
提出具体、可操作的改进建议——不只是“更小心地做”。例如，“使用光传感器和数据记录器来测量颜色变化，而不是凭肉眼判断。”
Comment on any anomalous results and try to give a reason, e.g., ‘The result for 40°C was much lower; this might have happened because the thermometer was read too early.’
对任何异常结果加以评论，并尝试给出原因，例如“40°C 的结果明显偏低；这可能是因为温度计读数过早”。
10. Common Practical Tasks | 常见实验任务
Testing how temperature affects dissolving: heat beakers of water to different temperatures, add a fixed mass of sugar, stir, and time how long it takes to dissolve.
测试温度对溶解的影响：将几杯水加热到不同温度，各加入固定质量的糖，搅拌并计时溶解所需时间。
Investigating springs: suspend a spring, hang masses from it, measure the new length each time, and plot extension (new length − original length) against force (weight of masses).
探究弹簧：悬挂弹簧，加挂砝码，每次测量新长度，并将伸长量（新长度−原长）与力（砝码重量）的关系画成图像。
Microscope work: prepare an onion epidermis wet mount, add a drop of iodine stain, and draw a labelled cell diagram showing cell wall, nucleus, cytoplasm, and cell membrane.
显微镜工作：制作洋葱表皮临时装片，加一滴碘液染色，绘制带标签的细胞图，标明细胞壁、细胞核、细胞质和细胞膜。
Separating mixtures: stir sand into water and filter through filter paper to collect sand; boil a salt solution to evaporate water and leave salt crystals behind.
分离混合物：将沙子与水泥合搅拌，用滤纸过滤收集沙子；煮沸食盐溶液，使水蒸发留下盐晶体。
Acid–alkali tests: dip blue and red litmus paper or add universal indicator to solutions; record colour changes and compare against a pH colour chart.
酸碱性测试：用蓝色和红色石蕊试纸浸入溶液，或加入通用指示剂；记录颜色变化并与pH色卡比对。
11. Exam Tips for Practical Questions | 实践题目考试技巧
Begin by identifying the command word: ‘plan’ means you write a method; ‘analyse’ means you read data or graphs; ‘evaluate’ means you discuss strengths, weaknesses, and improvements.
先识别指令词：“设计”意味着你要写方法；“分析”意味着阅读数据或图表；“评估”意味着讨论优缺点和改进。
When asked to describe a method, structure it as a logical sequence of steps – do not simply list equipment. Use phrases like ‘First, measure …’, ‘Next, add …’.
被要求描述方法时，应以合理步骤序列来组织——不要只是罗列器材。使用“首先，量取……”“接着，加入……”等句式。
In graph questions, always check that you have placed the independent variable on the x‑axis and labelled both axes with the variable name and unit.
在图表题中，务必检查已将自变量置于 x 轴，并给两轴都标上了变量名和单位。
For conclusion questions, structure your answer as ‘As [independent variable] increases, [dependent variable] increases/decreases’. Then quote some numbers from the table or graph.
对于结论题，按“随着[自变量]增加，[因变量]增加/减少”的句式组织答案，然后从表格或图表中引用一些数据。
In evaluation, always name a specific piece of equipment or a procedural change, e.g., ‘Use a syringe instead of a measuring cylinder for more accurate volume measurement.’
在评估中，一定要具体说出某一件装备或某个步骤的改变，例如“改用注射器代替量筒，以获得更精确的体积测量”。
If you cannot identify a trend, do not invent one. Instead write ‘There is no clear relationship between the variables, and further investigation with more data points is needed.’
如果无法识别趋势，不要编造。应写“变量之间无明显关系，需要用更多数据点做进一步探究”。
Published by TutorHao | Science Revision Series | aleveler.com
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