📚 Year 7 Cambridge Science: Key Points for Experiment/Practical Assessment | 剑桥7年级科学：实验/实践考核要点
Practical work is at the heart of Year 7 Cambridge Science. It is not just about ‘doing experiments’ but about learning how to think like a scientist. From safety and equipment handling to planning investigations and drawing conclusions, every practical skill is assessed in a way that prepares you for Checkpoint and beyond. This guide highlights the most important assessment points you need to master during your laboratory sessions.
实验操作是剑桥7年级科学的核心。它不仅仅是“做实验”，更是学习如何像科学家一样思考。从安全操作、仪器使用到设计调查和得出结论，每一项实践技能都会以评估的形式进行，为你准备Checkpoint考试及更高阶段的学习打下基础。本指南将重点介绍在实验室课程中必须掌握的关键考核要点。
1. Safety in the Lab | 实验室安全
Always wear safety goggles when handling chemicals, heating substances, or working with glassware. Your eyes must be protected from splashes, fumes and flying particles.
在处理化学品、加热物质或使用玻璃器皿时，必须佩戴护目镜。保护眼睛免受飞溅物、烟雾和飞散颗粒的伤害。
Tie back long hair and tuck in loose clothing or ties. This prevents them from catching fire on a Bunsen burner or getting caught in equipment.
扎起长发，并将宽松的衣服或领带塞好。这能防止它们在点燃的本生灯上着火或被设备卷入。
Never eat, drink or chew gum in the lab. Chemical residues can contaminate your food and make you very unwell.
绝对不要在实验室里吃东西、喝水或嚼口香糖。化学残留物会污染食物，导致严重不适。
Always point a test tube away from yourself and others when heating it. The contents may boil over or spurt out suddenly.
加热试管时，管口切勿朝向自己或他人。内容物可能沸腾并突然喷出。
Report any accident, spillage or broken glass to your teacher immediately. Do not try to clear up broken glass with bare hands; use a dustpan and brush.
任何事故、溢出或玻璃破碎都要立即报告老师。不要徒手清理碎玻璃，应使用簸箕和刷子。
Wash your hands thoroughly after every practical lesson, even if you think you have not touched any chemicals.
每次实验课后都要彻底洗手，即使你认为自己没有接触任何化学品。
2. Common Laboratory Equipment | 常见实验设备
A Bunsen burner is used for heating. You must know how to light it safely, adjust the air hole to get a blue roaring flame, and always close the air hole when the flame is yellow and luminous.
本生灯用于加热。你必须学会安全点燃它，调节气孔以获得蓝色强火焰，并在火焰呈黄色发光时立即关闭气孔。
A beaker is a wide glass container for mixing, heating and stirring liquids. It is not used for measuring volumes accurately.
烧杯是一种广口玻璃容器，用于混合、加热和搅拌液体。它不适合精确测量体积。
A measuring cylinder provides a much more accurate way to measure liquid volumes. Always read the volume at the bottom of the meniscus at eye level.
量筒能更精确地测量液体体积。读数时，视线应与凹液面最低处保持水平。
A thermometer measures temperature. Never stir with a thermometer and always hold it vertically in the liquid, waiting until the reading stabilises.
温度计用于测量温度。绝不能用温度计搅拌，应垂直放入液体中，等待读数稳定。
A stopwatch records time. Learn to start and stop it accurately; make sure you reset it to zero before each measurement.
秒表用于记录时间。要学会准确地开始和停止计时；每次测量前务必归零。
An electronic balance measures mass. Place a container on the pan and press ‘tare’ (zero) before adding the substance you wish to weigh.
电子天平用于测量质量。将容器放在称盘上，按“去皮”键归零后再加入要称量的物质。
3. Making Measurements | 进行测量
Length is usually measured in metres (m), centimetres (cm) or millimetres (mm) using a metre ruler. Always align the zero mark with one end and avoid parallax error by looking straight down at the scale.
长度通常用米尺以米(m)、厘米(cm)或毫米(mm)为单位进行测量。务必将零刻度线对准一端，并直视刻度以避免视差。
Mass is measured in grams (g) or kilograms (kg). Record the mass to the nearest 0.1 g or as precise as the balance allows. Do not forget to subtract the mass of the container.
质量以克(g)或千克(kg)为单位。记录质量时保留到0.1克或天平所能达到的精度。不要忘记减去容器的质量。
Volume of a liquid is measured in millilitres (ml) or cubic centimetres (cm^3). For irregular solids, use the displacement method: final volume minus initial volume equals the volume of the solid.
液体体积以毫升(ml)或立方厘米(cm³)为单位。对于不规则固体，使用排水法：最终体积减去初始体积即为固体体积。
Temperature is recorded in degrees Celsius (°C). Insert the thermometer bulb fully into the substance but not touching the bottom of the container. Wait for a steady reading.
温度以摄氏度(°C)为单位。将温度计感温泡完全浸入物质中但不接触容器底部。等待稳定读数。
Time is measured in seconds (s) or minutes (min). When measuring the period of a pendulum, time 10 complete swings and then divide by 10 to find the period for greater accuracy.
时间以秒(s)或分钟(min)为单位。测量单摆周期时，可计时10次完整摆动，然后除以10得到周期，以提高准确性。
4. Observations and Recording Data | 观察与记录数据
Qualitative observations describe what you see, hear or smell without using numbers. For example, ‘a white precipitate formed’ or ‘bubbles of gas were produced quickly’.
定性观察描述你看到、听到或闻到的东西，不使用数字。例如“生成白色沉淀”或“迅速产生气泡”。
Quantitative observations involve numerical data. Always include the correct unit and an appropriate degree of precision. For example, ‘the temperature rose by 12.5 °C’.
定量观察涉及数字数据。始终要包括正确的单位和适当的精确度。例如“温度升高了12.5°C”。
Design a results table before starting the experiment. The first column lists the independent variable, and the second (or more) columns contain repeated readings for the dependent variable and a column for the average (mean).
在实验开始前设计好结果表。第一列列出自变量，第二列（或更多列）包含因变量的重复读数以及一列平均值。
All columns must have clear headings with units separated by a slash or given in brackets. For instance, ‘Time / s’ or ‘Length (cm)’. Never write units in the data cells.
所有列必须有清晰的标题，单位用斜线分隔或写在括号内。例如“时间 / s”或“长度(cm)”。绝不在数据单元格内再次书写单位。
Repeating readings improves reliability. If one reading looks very different from the others, it may be an anomaly; record it but consider excluding it from the mean if there is a clear reason.
重复读数可提高信度。如果某个读数与其他读数差异很大，可能是异常值；记录下来，如果有明确原因，可在计算平均值时将其排除。
5. Variables in Experiments | 实验中的变量
The independent variable is the factor you deliberately change or select. In an investigation of how light intensity affects photosynthesis, light intensity is the independent variable.
自变量是你刻意改变或选择的因素。在研究光照强度如何影响光合作用的调查中，光照强度是自变量。
The dependent variable is what you measure or observe as a result. In the same experiment, the number of oxygen bubbles produced per minute would be the dependent variable.
因变量是你测量或观察的结果。在同一实验中，每分钟产生的氧气泡数量就是因变量。
Control variables are factors you keep the same to make the test fair. Examples include temperature, carbon dioxide concentration, type of plant and the distance of the light source must be kept constant except for the independent variable.
控制变量是那些你保持不变以确保公平测试的因素。例如，温度、二氧化碳浓度、植物种类和光源距离等都必须保持不变（自变量除外）。
Sometimes a control experiment is also set up where the independent variable is removed or set to zero, to show that it is the only factor causing the effect.
有时也会设置对照实验，去除自变量或将其设为零，以证明这是造成影响的唯一因素。
When writing your method, describe exactly how you will change and measure the independent and dependent variables, and list all the controls you will put in place.
在写实验步骤时，要准确描述你将如何改变和测量自变量与因变量，并列出所有将到位的控制条件。
6. Planning a Fair Test | 设计公平实验
A fair test is one where only the independent variable is allowed to influence the dependent variable. All other factors are kept constant.
公平实验是指只允许自变量影响因变量，其他所有因素都保持不变。
Change one variable at a time. If you alter both temperature and light at once, you cannot tell which one caused the change in your results.
每次只改变一个变量。如果同时改变温度和光照，就无法判断是哪一项导致了结果的变化。
Include a clear step-by-step method written in the third person and past tense when reporting, but use imperative (command) verbs in the plan: ‘Add 10 ml of water to the beaker.’
计划步骤时应使用清晰的、按顺序的说明，报告中可使用第三人称过去式，但在计划阶段使用祈使动词，例如：“量筒中加入10毫升水”。
Choose a suitable range and interval for the independent variable. For example, testing salt concentration from 0% to 10% in steps of 2% gives enough data points to plot a graph.
为自变量选择合适的范围和间隔。例如，测试盐浓度从0%到10%，以2%为间隔，可提供足够的数据点来绘制图表。
Use appropriate equipment and consider safety. Mention any protective gear, how you will handle hot objects, and what you will do with waste materials.
使用合适的设备并考虑安全。提及任何防护装备、如何处理热物体，以及废物如何处理。
7. Presenting Data | 呈现数据
Bar charts are used when the independent variable is categorical or discrete (e.g. type of material, colour). The bars do not touch each other.
当自变量为类别或离散变量时（如材料种类、颜色）使用条形图。柱条之间不相接触。
Line graphs are drawn when both variables are continuous (e.g. temperature over time). Plot the independent variable on the x-axis (horizontal) and the dependent on the y-axis (vertical).
当两个变量均为连续变量时（如温度随时间变化）绘制线形图。将自变量放在x轴（横轴），因变量放在y轴（纵轴）。
Every graph must have a proper title that describes what it shows, such as ‘Graph to show how temperature affects the rate of reaction’.
每张图表必须有一个合适的标题，描述所显示的内容，例如“显示温度如何影响反应速率的图表”。
Label both axes clearly with the quantity and unit. Choose sensible scales that spread your data points over more than half of each axis. Avoid awkward scales like 3s or 7s.
两条坐标轴都要清晰标注数量和单位。选择合理的刻度，使数据点分布超过每轴的一半区域。避免使用诸如3或7之类难读的刻度。
Draw the best-fit line or curve; this does not necessarily join all points but shows the trend. Identify and circle any anomalous points, and do not include them in the line of best fit.
绘制最佳拟合线或曲线；不一定连接所有点，但能显示趋势。圈出任何异常点，并且不将其包含在最佳拟合线中。
8. Drawing Conclusions | 得出结论
Start by describing the pattern you see in the data. Use the sentence stem: ‘As the [independent variable] increases, the [dependent variable] increases/decreases.’
首先描述数据中看到的模式。使用句型：“随着[自变量]增加，[因变量]增加/减少。”
If the line on a graph flattens out, you might say, ‘The dependent variable reaches a maximum and then levels off.’ Explain what this means in terms of the science involved.
如果图表上的线条趋于平缓，你可以说：“因变量达到最大值后趋于平稳。”根据所涉及的科学原理解释其含义。
Always refer to specific data from your results table or graph to support your conclusion. For example, ‘The number of bubbles increased from 5 per minute at 20 °C to 28 per minute at 30 °C.’
始终引用结果表或图表中的具体数据来支持结论。例如，“气泡数量从20°C时的每分钟5个增加到30°C时的每分钟28个。”
Your conclusion should answer the original question or prove/disprove the hypothesis you made at the start of the investigation.
你的结论应回答最初的问题，或证明/反驳你在调查开始时提出的假设。
Never go beyond the data you have collected. Avoid making claims you cannot support. If your results only cover a range from 0 to 40 °C, do not predict what would happen at 100 °C.
切勿超出你所收集的数据范围。避免做出无法证实的论断。如果结果只涵盖0至40°C的范围，就不要预测100°C时会发生什么。
9. Evaluating the Investigation | 评估调查
Evaluation is about judging how good your data is. Look at the spread of repeat readings: if they are close together, your data is precise. If they match the true value, it is accurate.
评估就是判断数据的质量。观察重复读数的分布：如果它们很接近，数据就精确。如果与真实值一致，数据就准确。
Identify any anomalous results. An anomaly is a measurement that does not fit the overall pattern. Suggest a possible cause, such as a misread stopwatch or a spill.
找出任何异常结果。异常值是指不符合整体模式的测量值。提出可能的原因，比如秒表错误读数或液体溢出。
Discuss sources of error. These are not mistakes you made but limitations of the procedure or equipment, like the difficulty in judging the end point of a reaction, or heat loss to the surroundings.
讨论误差来源。这些不是你犯的错误，而是步骤或设备的局限性，例如难以判断反应的终点，或热量散失到环境中。
Finally, suggest practical improvements. Use phrases like ‘Use a more sensitive thermometer’, ‘Insulate the beaker’, or ‘Repeat the experiment at 5 °C intervals to get more detail’.
最后，提出实际的改进建议。使用诸如“使用更灵敏的温度计”、“给烧杯隔热”或“以5°C为间隔重复实验以获取更多细节”等表达。
In an exam-style evaluation, credit is given for identifying a specific limitation and proposing a realistic, well-explained improvement.
在考试风格的评估中，识别出一个具体的局限性并提出切实可行、解释清晰的改进措施，就能获得分数。
10. Common Mistakes and Tips for Success | 常见错误与成功技巧
Parallax error when reading volumes: always bring your eye down to the level of the meniscus on a flat surface. This simple step can dramatically improve accuracy.
读取体积时的视差错误：始终将视线降到与水平面上的凹液面等高。这简单的一步能大幅提高准确性。
Forgetting to zero the balance or not subtracting the mass of the container leads to systematic errors in all your mass readings.
忘记将天平归零或不减去容器质量，会导致所有质量读数出现系统误差。
Rushing to light a Bunsen burner without checking that the air hole is closed can produce a hot, invisible flame that is dangerous. Always start with a yellow safety flame.
未检查气孔是否关闭就匆忙点燃本生灯，可能产生危险且看不见的高温火焰。务必从黄色的安全火焰开始。
Using units incorrectly: never write ‘12.5 gms’ for grams; it is simply ‘12.5 g’. Keep the notation consistent, and always separate the number and unit with a space, e.g. ’25 cm^3′.
错误使用单位：克的符号是“g”，不要写成“gms”。保持符号一致，数字和单位之间始终留一个空格，例如“25 cm³”。
Drawing graphs with no title, missing axis labels, or using unlabelled scales are among the most frequent reasons for losing marks in practical-based questions.
图表无标题、缺少坐标轴标签或使用未标注的刻度，是实践类题目中最常见的失分原因之一。
Finally, always read through your planned method before starting. Run it in your head: does it actually test what you want to test? A little thought before the experiment saves a lot of trouble afterwards.
最后，开始前通读计划好的步骤。在脑海中演练一遍：这真的能测试你想要测试的内容吗？实验前多想一想，能避免之后的许多麻烦。
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