📚 Doing an Investigation in Chemistry | 化学探究实践
In KS3 Chemistry, doing an investigation is not just about mixing chemicals and watching what happens. It is a structured process that helps you answer a scientific question using evidence. This guide explains each step, from planning a fair test to evaluating your results, with chemical examples throughout.
在 KS3 化学中，进行探究不只是混合化学试剂并观察现象。它是一个有结构的过程，帮助我们用证据回答科学问题。本指南将逐步解释从设计公平实验到评估结果的每个环节，并贯穿化学示例。
1. What is a scientific investigation? | 什么是科学探究？
A scientific investigation is a way of testing an idea by collecting reliable data. In chemistry, you might investigate how temperature affects a reaction or which salt dissolves fastest. The aim is to find patterns and use them to support or reject a prediction.
科学探究是一种通过收集可靠数据来检验想法的方法。在化学中，你可以探究温度如何影响反应，或哪种盐溶解最快。目的是寻找规律，并用它们支持或否定预测。
Every investigation follows a similar cycle: ask a question, plan the method, collect data, analyse the data, and evaluate the method. This makes your results more believable.
每次探究都遵循相似的循环：提出问题、设计方法、收集数据、分析数据和评估方法。这让结果更可信。
2. Asking a testable question | 提出可检验的问题
A good investigation starts with a question that can be tested by experiment. It usually contains two variables and is specific. For example: ‘How does increasing the temperature of water affect the time taken for 5 g of sugar to dissolve?’
好的探究始于一个可通过实验检验的问题。它通常包含两个变量，并且很具体。例如：“将水温升高会如何影响 5 g 糖溶解所需的时间？”
Avoid vague questions such as ‘What happens when I heat things?’ because they do not tell you what to measure or change.
避免模糊的问题，如“加热东西会怎样？”，因为这种问题没有说明要改变或测量什么。
3. Making a prediction and hypothesis | 作出预测与假设
A prediction states what you think will happen and why, based on scientific knowledge. A hypothesis often uses the format: ‘If I change the independent variable, then the dependent variable will change because …’
预测说明你认为会发生什么及其原因，并基于科学知识。假设常用句式：“如果我改变自变量，那么因变量会改变，因为……”
Example: ‘If the acid concentration increases, then the reaction with magnesium will produce gas faster because there are more acid particles per unit volume to collide with the metal.’ This gives a testable reason.
例如：“如果酸的浓度增加，那么镁与酸的反应产生气体更快，因为单位体积内有更多酸粒子与金属碰撞。”这给出了可检验的理由。
4. Identifying variables | 识别变量
Variables are the things that can change in an experiment. The independent variable is what you change deliberately. The dependent variable is what you measure or observe. Control variables are all the other factors you keep the same.
变量是实验中可以改变的因素。自变量是你有意改变的量；因变量是你测量或观察的量；控制变量是你保持不变的所有其他因素。
In the sugar dissolving investigation, the independent variable is water temperature. The dependent variable is the time taken for sugar to dissolve. Control variables include the volume of water, the mass of sugar, the type of sugar, and how the mixture is stirred.
在糖溶解探究中，自变量是水温；因变量是糖溶解所需的时间；控制变量包括水的体积、糖的质量、糖的种类以及搅拌方式。
5. Designing a fair test | 设计公平实验
A fair test means changing only the independent variable and keeping everything else the same. If you change two variables at once, you cannot tell which one caused the effect.
公平实验意味着只改变自变量，其余保持不变。如果一次改变两个变量，就无法判断是哪个造成了效应。
To make the sugar test fair, use the same beaker size, the same stirring speed, and the same volume of water each time. Only change the temperature.
为了使糖溶解实验公平，每次使用相同大小的烧杯、相同的搅拌速度和相同体积的水。只改变温度。
6. Choosing equipment and safety | 选择仪器与安全
Choose equipment that is sensitive enough for your measurements. Use a thermometer for temperature, a measuring cylinder for volume, and a stopwatch for time. Repeat measurements to check they are consistent.
选择对测量足够灵敏的仪器。用温度计测温度，用量筒测体积，用秒表测时间。重复测量以检查数据是否一致。
Always follow safety rules: wear safety goggles, tie back long hair, and handle acids or hot water with care. In a chemistry lab, never taste chemicals and always wash hands after an investigation.
始终遵守安全规则：佩戴护目镜、扎起长发、小心处理酸或热水。在化学实验室中，绝不可品尝化学品，实验后务必洗手。
7. Recording results | 记录结果
Record your results in a table as soon as you collect them. Include units in the headings, for example ‘Temperature (°C)’ and ‘Time to dissolve (s)’. This makes your data easy to read.
收集数据后立即记录在表格中。在表头注明单位，例如“温度（°C）”和“溶解时间（s）”。这样数据更易读。
Repeat the experiment at least three times for each value and calculate a mean. This reduces the effect of random errors. If one repeat is very different, look for an obvious mistake before deciding whether to discard it.
每个数值至少重复实验三次并计算平均值。这可以减少随机误差的影响。如果某次重复数据差异很大，先检查是否有明显错误，再决定是否剔除。
mean = (reading 1 + reading 2 + reading 3) ÷ 3
8. Presenting data in tables and graphs | 用表格和图表呈现数据
A results table should have clear headings, units, and space for repeated readings and the mean. Use a ruler to keep the table neat.
结果表应有清晰的表头、单位，并为重复读数和平均值留出空格。用直尺保持表格整齐。
To show a trend, draw a line graph if the independent variable is continuous, such as temperature. Plot the independent variable on the x-axis and the dependent variable on the y-axis. Label both axes with units.
为了显示趋势，如果自变量是连续的（如温度），可绘制折线图。将自变量标在 x 轴，因变量标在 y 轴。两轴都需注明单位。
For example, a line graph of temperature against dissolving time can show whether the time decreases steadily as temperature rises. A smooth curve or best-fit line helps you see the pattern more clearly than the points alone.
例如，温度对溶解时间的折线图可以显示时间是否随温度升高而稳定减少。光滑曲线或最佳拟合线比仅看点更能帮助你看出规律。
9. Drawing conclusions | 得出结论
A conclusion describes the pattern in your data and states whether it supports your prediction. Use scientific language and refer to the actual results, for example: ‘As the water temperature increased from 20 °C to 60 °C, the time for sugar to dissolve decreased from 95 s to 42 s.’
结论描述数据中的规律，并说明是否支持你的预测。使用科学语言并引用实际结果，例如：“当水温从 20 °C 升高到 60 °C 时，糖溶解时间从 95 s 缩短到 42 s。”
A conclusion should not go beyond the data. If you only tested between 20 °C and 60 °C, you cannot claim the trend continues forever.
结论不应超出数据范围。如果你只测试了 20 °C 到 60 °C，就不能声称该趋势会永远持续。
10. Evaluating the investigation | 评估探究
Evaluation means thinking about how reliable and accurate your results are. Ask: Did I control all the variables? Were the measurements precise? Were there any anomalies?
评估意味着思考你的结果有多可靠和准确。问自己：我控制所有变量了吗？测量精确吗？有没有异常值？
You can improve the method by using more precise instruments, taking more repeats, or using a data logger to record temperature changes automatically.
你可以通过使用更精密的仪器、进行更多重复实验，或使用数据记录仪自动记录温度变化来改进方法。
11. Common errors and how to reduce them | 常见误差及减少方法
Random errors cause readings to be scattered around the true value, such as pressing the stopwatch slightly late. Taking repeats and calculating a mean reduces random errors.
随机误差导致读数在真值附近波动，例如按秒表稍晚。多次重复并计算平均值可以减少随机误差。
Systematic errors cause all readings to be shifted by the same amount, such as a thermometer that reads 2 °C too high. Check instruments or compare with known values to spot systematic errors.
系统误差导致所有读数向同一方向偏移，例如温度计读数偏高 2 °C。检查仪器或与已知值比较可发现系统误差。
Anomalies are results that do not fit the pattern. Mark them clearly and, if possible, repeat that measurement. Do not include anomalies in your mean without a reason.
异常值是不符合规律的结果。清楚标出它们，如有可能则重复该测量。没有理由不要把异常值计入平均值。
12. Example investigation: temperature and dissolving rate | 示例探究：温度与溶解速率
Here is a simple KS3 chemistry investigation. Question: How does water temperature affect the time taken for 5 g of table salt to dissolve in 100 cm³ of water?
这里是一个简单的 KS3 化学探究。问题：水温如何影响 5 g 食盐在 100 cm³ 水中溶解所需的时间？
Method: Measure 100 cm³ of water at 20 °C using a measuring cylinder. Add 5 g of salt. Stir gently at a steady speed. Start the stopwatch when the salt is added and stop it when no solid is visible. Repeat at 30 °C, 40 °C, 50 °C, and 60 °C. Do three repeats at each temperature and record the mean time.
方法：用量筒量取 20 °C 的水 100 cm³，加入 5 g 盐。以稳定速度轻轻搅拌。加入盐时启动秒表，当看不到固体时停止。在 30 °C、40 °C、50 °C 和 60 °C 下重复实验。每个温度重复三次并记录平均时间。
Expected conclusion: As temperature increases, dissolving time decreases, because particles move faster and collide with the salt more often.
预期结论：随着温度升高，溶解时间缩短，因为粒子运动更快，与盐的碰撞更频繁。
Evaluation: The stirring speed is difficult to keep exactly the same, so a magnetic stirrer could improve control. A digital thermometer would give more precise temperatures than a glass thermometer.
评估：搅拌速度很难保持完全相同，因此磁力搅拌器可以改善控制。数字温度计比玻璃温度计提供更精确的温度。
Published by TutorHao | Chemistry Revision Series | aleveler.com
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