📚 Planning Investigations and Collecting Evidence | 规划探究与收集证据
Planning an investigation is a key skill in chemistry. Before mixing chemicals or heating substances, scientists decide what question to ask, which variable to change, what to measure, and how to keep the test fair. Collecting evidence carefully allows you to draw conclusions that are backed by data, not guesses.
规划探究是化学中的关键技能。在混合化学品或加热物质之前，科学家要先确定要研究的问题、改变哪个变量、测量什么，以及如何保持测试公平。认真收集证据能让你根据数据而非猜测得出结论。
1. What is a Scientific Investigation? | 什么是科学探究？
A scientific investigation is a structured enquiry that aims to answer a specific question about the natural world. In chemistry, investigations often explore how changing one factor affects another, such as how temperature affects the rate of dissolving. Planning ahead makes your evidence more reliable because you think carefully about what to change, what to keep the same and how to record results.
科学探究是一种有结构的探究活动，旨在回答关于自然界的特定问题。在化学中，探究通常探索改变一个因素如何影响另一个因素，例如温度如何影响溶解速率。提前规划会让证据更可靠，因为你会认真思考要改变什么、保持不变什么以及如何记录结果。
2. Variables: Independent, Dependent and Control | 变量：自变量、因变量与控制变量
Variables are quantities that can change during an experiment. The independent variable is the one you deliberately change, such as the temperature of water. The dependent variable is the one you measure or observe, such as the time taken for a salt to dissolve. Control variables are all the other factors you keep the same, such as the volume of water and the mass of salt, so that the test is fair.
变量是在实验中可能发生变化的量。自变量是你有意改变的量，例如水的温度。因变量是你测量或观察的量，例如盐溶解所需的时间。控制变量是你保持相同的所有其他因素，例如水的体积和盐的质量，这样测试才是公平的。
- Independent variable: the factor you change
- Dependent variable: the factor you measure
- Control variables: the factors you keep constant
自变量：你改变的因素；因变量：你测量的因素；控制变量：你保持不变的因素。
3. Writing a Clear Aim and Hypothesis | 撰写明确目的与假设
An aim states the purpose of the investigation. A good aim often begins with ‘To investigate the effect of… on…’. For example: To investigate the effect of water temperature on the time taken for salt to dissolve. A hypothesis is a prediction that suggests a relationship and gives a scientific reason. For example: If the water temperature increases, then the salt will dissolve faster because particles have more kinetic energy.
目的说明探究的意图。好的目的通常以 “研究……对……的影响” 开头。例如：研究水温对盐溶解所需时间的影响。假设是一个预测，它提出关系并给出科学理由。例如：如果水温升高，那么盐会溶解得更快，因为粒子具有更多动能。
4. Choosing Apparatus and Methods | 选择仪器与方法
Choose apparatus that is suitable for the measurements you need. Use a thermometer to measure temperature in degrees Celsius, a measuring cylinder to measure volume in cm³, a balance to measure mass in grams, and a stopwatch to measure time in seconds. Write the method as numbered steps, using clear commands such as ‘Measure 100 cm³ of water’ and ‘Record the temperature every 10 seconds’. The method should allow another person to repeat the experiment exactly.
选择适合所需测量的仪器。用温度计测量以摄氏度为单位，用量筒测量体积（cm³），用天平测量质量（克），用秒表测量时间（秒）。将方法写成编号步骤，使用清晰的指令，例如 “量取 100 cm³ 水” 和 “每 10 秒记录一次温度”。方法应能让另一个人完全重复该实验。
5. Risk Assessment and Safety | 风险评估与安全
Before starting, identify hazards and plan how to reduce risk. In chemistry, hazards may include hot liquids, glassware, acids and alkalis. Control measures include wearing safety goggles, tying back long hair, standing up during practical work, and using tongs to handle hot apparatus. If a chemical spills, tell the teacher immediately. A risk assessment does not need to be long, but it must be complete.
开始之前，识别危险并计划如何降低风险。在化学中，危险可能包括热液体、玻璃器皿、酸和碱。控制措施包括佩戴护目镜、扎起长发、实验时站立并用坩埚钳处理热仪器。如果化学品洒出，立即告诉老师。风险评估不需要很长，但必须完整。
6. Making Measurements and Observations | 进行测量与观察
Evidence can be quantitative (measurements with numbers and units) or qualitative (observations described in words). When reading a measuring cylinder, look at the bottom of the liquid curve, called the meniscus, at eye level to avoid parallax error. Record the unit with every measurement. Qualitative observations might include colour changes, bubbles of gas, or a precipitate forming.
证据可以是定量的（带数字和单位的测量）或定性的（用文字描述的观察）。读取量筒时，在视线水平处观察液体曲线底部，即弯月面，以避免视差误差。每次测量都要记录单位。定性观察可能包括颜色变化、气体气泡或沉淀形成。
A simple rate calculation can be shown as:
简单的速率计算可表示为：
mean rate = quantity of product formed ÷ time taken
平均速率 = 生成物数量 ÷ 所用时间。
7. Recording Data in Tables | 用表格记录数据
Data should be recorded in a ruled table as soon as it is collected. The first column usually shows the independent variable. The next columns show repeated readings of the dependent variable and, if useful, a mean. Headings must include the quantity and unit, for example ‘Temperature (°C)’ and ‘Time to dissolve (s)’. Do not put units in every cell.
收集数据后应立即记录在带格线的表格中。第一列通常显示自变量。接下来几列显示因变量的重复读数和如有用的平均值。表头必须包含量和单位，例如 “温度（°C）” 和 “溶解时间（s）”。不要在每个单元格中写单位。
| Temperature (°C) | Time to dissolve – trial 1 (s) | Time to dissolve – trial 2 (s) | Mean time (s) |
|---|---|---|---|
| 20 | 85 | 89 | 87 |
| 40 | 42 | 44 | 43 |
| 60 | 21 | 19 | 20 |
该表显示自变量温度在第一列，因变量溶解时间在后续列，并计算平均值。
8. Repeatability, Reproducibility and Anomalies | 可重复性、复现性与异常值
Repeat readings make evidence more reliable. If repeated measurements by the same person using the same method are close, results are repeatable. If a different group obtains similar results using the same method, results are reproducible. An anomaly is a result that does not fit the pattern. When calculating a mean, exclude anomalies and repeat the measurement if possible.
重复读数使证据更可靠。如果同一人使用相同方法得到的重复测量结果接近，结果具有可重复性。如果不同小组使用相同方法得到相似结果，结果具有可复现性。异常值是不符合规律的结果。计算平均值时，排除异常值，并在可能的情况下重新测量。
9. Accuracy, Precision and Errors | 准确度、精密度与误差
Accuracy describes how close a measurement is to the true value. Precision describes how close repeated measurements are to each other. Low accuracy can be caused by a systematic error, such as a thermometer that always reads 2 °C too high. Low precision can be caused by random errors, such as judging the end point by eye. Using instruments with smaller scale divisions can improve precision.
准确度描述测量值与真实值的接近程度。精密度描述重复测量值彼此之间的接近程度。准确度低可能由系统误差引起，例如温度计总是高出 2 °C。精密度低可能由随机误差引起，例如用肉眼判断终点。使用刻度分度更小的仪器可以提高精密度。
10. Fair Testing and Controls | 公平测试与对照
A fair test changes only the independent variable and keeps all control variables constant. For example, when testing how temperature affects the rate of a reaction, keep the same concentration of acid, the same reactant masses and the same stirring method. If more than one variable changes, you cannot know which one caused the effect. A control experiment can also be used as a baseline, such as repeating the procedure without the reactant being tested.
公平测试只改变自变量，并保持所有控制变量不变。例如，在测试温度如何影响反应速率时，保持酸浓度
Published by TutorHao | KS3 Chemistry 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