IGCSE Edexcel Science Command Words Explained | IGCSE Edexcel 科学命令词详解

📚 IGCSE Edexcel Science Command Words Explained | IGCSE Edexcel 科学命令词详解

In IGCSE Edexcel Science exams, command words tell you exactly what the examiner expects. Many students lose marks simply because they misread the instruction. This guide explains the most common command words in Biology, Chemistry and Physics, with worked examples and exam tips, so you can answer precisely and confidently.

在 Edexcel IGCSE 科学考试中，命令词告诉考官期待你给出什么样类型的答案。许多学生丢分只是因为读错了指令。本指南将解释生物、化学和物理中最常见的命令词，并提供例题和答题技巧，帮助你精准作答、自信应试。

1. Why Command Words Matter | 1. 为什么命令词如此重要

Each command word has a specific meaning. “State” expects a short, factual answer, while “Evaluate” expects a balanced judgement with evidence. Using the wrong kind of answer loses marks.

每个命令词都有特定含义。“State”期待简短、事实性答案，而“Evaluate”期待有证据的平衡判断。回答类型不对就会丢分。
Mark schemes are based on command words. If a question says “Describe” and you write “Because…” without actually describing the observation, you will miss the description marks.

评分标准基于命令词。如果题目要求“Describe”，而你只写“因为……”而没有描述观察结果，就会丢失描述分数。
Command words also control the number of marks. A 2-mark “Explain” question usually needs a statement plus a reason, whereas a 2-mark “State” question may need two separate facts.

命令词还控制分数分配。2 分的“Explain”题通常需要“结论＋理由”，而 2 分的“State”题可能只需要两个独立的事实。

2. State / Give / Name | 2. 陈述 / 给出 / 命名

What to do: Write a short, factual answer. No explanation is needed unless the question adds “give a reason”. For example: “State the unit of force.” The answer is simply “newton” or “N”.

做什么：写一个简短、事实性的答案。除非题目额外要求“给出理由”，否则不需要解释。例如：“State the unit of force.” 答案是 “newton” 或 “N”（牛）。

Example (Chemistry): “Name the gas produced when dilute hydrochloric acid reacts with magnesium.” Answer: “hydrogen” (H₂).

化学示例：“Name the gas produced when dilute hydrochloric acid reacts with magnesium.”（稀盐酸与镁反应产生什么气体？）答案：“hydrogen”（氢气，H₂）。

Exam tip: If asked to “State”, keep your answer below one sentence. Extra statements can lead to contradictions, which may lose marks.

考试提示：如果被要求“State”，答案不要超过一句话。额外补充与答案矛盾的内容反而会扣分。

3. Describe | 3. 描述

What to do: Give an account of what happens, what you see, or what a graph shows. Do NOT give reasons unless the question asks “explain why”. In graph questions, “describe” means you should state the trend or relationship, often using data.

做什么：说明发生了什么、你看到了什么，或图表显示了什么。除非题目要求“解释为什么”，否则不要写原因。在图表题中，“Describe”意味着你应说明趋势或关系，通常要引用数据。

Example (Biology): “Describe the effect of temperature on enzyme activity between 0 °C and 60 °C.” A good answer: “As temperature increases from 0 °C to around 40 °C, the rate of enzyme activity increases. Above 40 °C, the rate decreases sharply and reaches zero at about 60 °C.”

生物示例：“Describe the effect of temperature on enzyme activity between 0 °C and 60 °C.”（描述温度对酶活性的影响，温度范围 0 °C 到 60 °C。）好的答案：“随着温度从 0 °C 升到约 40 °C，酶活性加快。超过 40 °C 后，酶活性急剧下降，到约 60 °C 时降为零。”

Always include numbers: If the question provides a table or graph, quote the values. “The rate increases from 2 cm³/s to 8 cm³/s” is better than “the rate increases”.

一定要引用数据：如果题目提供表格或图形，请使用具体数值。与其说“速率增加”，不如说“速率从 2 cm³/s 增加到 8 cm³/s”。

4. Explain | 4. 解释

What to do: Give reasons or causes, using scientific ideas or theory. You must link the observation to an underlying mechanism. A common structure is: “This is because…” followed by a scientific reason.

做什么：用科学原理给出理由或原因。你必须将现象与底层机制联系起来。常用结构是：“这是因为……”后接科学理由。

Example (Physics): “Explain why a skydiver reaches terminal velocity.” A good answer: “As the skydiver falls, air resistance increases. Eventually air resistance becomes equal to the force of gravity, so the resultant force is zero. The skydiver then falls at a constant speed.”

物理示例：“Explain why a skydiver reaches terminal velocity.”（解释为什么跳伞运动员会达到终端速度。）好的答案：“随着跳伞者下降，空气阻力增大。最终空气阻力等于重力，因此合力为零。之后跳伞者以恒定速度下落。”

2-mark tip: A 2-mark “Explain” question usually requires one point plus one reason. Write “Result” + “Because”. Don’t just repeat the question.

2 分题技巧：2 分的“Explain”题通常需要“一个结果＋一个原因”。写“结果＋因为”，不要简单重复题目。

5. Suggest | 5. 推测 / 建议

What to do: “Suggest” asks you to use your knowledge to propose a possible explanation or idea, even if it is not directly taught. There may be more than one valid answer. You should apply scientific principles to a new context.

做什么：“Suggest”要求你运用所学知识提出一种可能的解释或想法，即使这个内容不是课本直接讲过的。可能不止一个正确答法。你需要将科学原理应用于新情境。

Example (Biology): “Suggest why some plants in a desert have very small leaves.” Possible answer: “To reduce water loss by transpiration because a smaller leaf surface area means less evaporation.”

生物示例：“Suggest why some plants in a desert have very small leaves.”（推测为什么沙漠中有些植物叶子非常小。）可能的答案：“为了减少蒸腾作用导致的水分散失，因为叶面积越小，蒸发越少。”

Evidence matters: In “suggest” questions, give a logical reason. Use “because” to show your thinking. If you can, relate it to a concept you already know.

证据很重要：在“Suggest”题中，请给出逻辑理由。用“因为”展示你的思路。如果可以，联系你已知的概念。

6. Calculate | 6. 计算

What to do: Perform a numerical calculation. You need to choose the correct formula, substitute values, work out the answer, and include units. Show your working because mark schemes often give method marks.

做什么：进行数值计算。你需要选择正确的公式、代入数值、算出答案并带单位。要写出计算过程，因为评分标准常给方法分。

Example (Physics): A car travels 150 m in 5 s. Calculate its speed. Use: speed = distance ÷ time = 150 ÷ 5 = 30 m/s. Always write the final unit.

物理示例：一辆汽车 5 秒内行驶 150 米。计算它的速度。使用：speed = distance ÷ time = 150 ÷ 5 = 30 m/s（米每秒）。一定要写最终单位。

speed (m/s) = distance (m) ÷ time (s)

Significant figures: If the data has 2 significant figures, give your answer to 2 significant figures. For example, 5.0 A × 2.0 Ω = 10 V (not 10.0 V unless asked).

有效数字：如果题目数据有 2 位有效数字，答案也应保留 2 位有效数字。例如：5.0 A × 2.0 Ω = 10 V（除非题目要求，否则不必写 10.0 V）。

7. Compare / Contrast | 7. 比较 / 对比

What to do: Give similarities and differences. A comparison without a “same” or “different” statement is incomplete. Use comparative language such as “whereas”, “however”, “both”, “unlike”.

做什么：给出相同点和不同点。没有“相同”或“不同”表述的对比是不完整的。请使用比较语言，例如“而”“然而”“两者都”“与……不同”。

Example (Chemistry): “Compare the structures of diamond and graphite.” A good answer: “Both are forms of carbon with giant covalent structures. In diamond, each carbon atom forms four strong covalent bonds, making it very hard. In graphite, each carbon atom forms three bonds, arranged in layers, so graphite is soft and slippery.”

化学示例：“Compare the structures of diamond and graphite.”（比较金刚石和石墨的结构。）好的答案：“两者都是碳的同素异形体，具有巨大的共价结构。金刚石中每个碳原子形成四个强共价键，因此非常硬。石墨中每个碳原子形成三个共价键，呈层状排列，因此柔软润滑。”

Structure your answer: Start with “Both…” for similarity, then “However, … whereas …” for difference. Aim for the number of points equal to the marks.

组织答案：先写“两者都……”表示相同点，再用“然而……而……”表示不同点。得分点数量应与题目分值匹配。

8. Evaluate / Discuss | 8. 评估 / 讨论

What to do: Look at both sides, weigh pros and cons, then reach a final judgement. “Evaluate” often appears in practical investigation or ethical context questions. You must use evidence or data to support your judgement.

做什么：权衡利弊，考虑正反两面，然后做出最终判断。“Evaluate”常出现在实验或伦理背景题中。你必须用证据或数据支持判断。

Example (Biology): “Evaluate whether a vaccine programme is better than antibiotics for controlling a disease.” A good answer would mention advantages of vaccines (prevention, herd immunity) and disadvantages (cost, cannot cure existing infection), then conclude: “On balance, vaccines are better for long-term control, but antibiotics are needed for current cases.”

生物示例：“Evaluate whether a vaccine programme is better than antibiotics for controlling a disease.”（评估疫苗接种计划是否比抗生素更有利于控制疾病。）好的答案应提到疫苗的优点（预防、群体免疫）和缺点（费用较高、不能治疗已感染的人），然后总结：“总体而言，疫苗更有利于长期控制，但抗生素仍用于治疗现有病例。”

Signpost your opinion: Use phrases like “This suggests…”, “Therefore…”, “On balance…” to show your final decision.

给出判断：使用“这表明……”“因此……”“总体而言……”等短语展示最终决定。

9. Define / Outline | 9. 定义 / 概述

Define: Give a precise, short scientific meaning. For example: “Define osmosis.” Answer: “The net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane.”

定义：给出准确、简短的科学含义。例如：“Define osmosis.”（定义渗透作用。）答案：“水分子通过部分通透膜从水势高区域向水势低区域的净移动。”

Outline: Give the main points or steps, without full detail. Think of it as a summary. For example: “Outline the steps in the PCR method.” You would list denaturation, annealing and extension in one or two sentences each.

概述：给出主要点或步骤，不需要完整细节。把它看作摘要。例如：“Outline the steps in the PCR method.”（概述 PCR 方法的步骤。）你可以用一两句话分别列出变性、退火和延伸。

Think about depth: “Define” requires one or two marks; “Outline” might require 3–4 marks. Do not overwrite for “define”. Do not leave out necessary steps for “outline”.

注意深度：“Define”只需要 1–2 分；“Outline”可能需要 3–4 分。做“Define”时不要过度展开；做“Outline”时不要漏掉必要步骤。

10. Predict / Deduce | 10. 预测 / 推论

Predict: Use patterns, trends or general knowledge to suggest what will happen. You may need to make an estimate. For example: “Predict how the rate of gas production changes after 5 minutes.” You answer: “It decreases because the reactants are used up.”

预测：利用规律、趋势或常识推测会发生什么。你可能需要估算。例如：“Predict how the rate of gas production changes after 5 minutes.”（预测 5 分钟后气体生产速率如何变化。）你回答：“速率下降，因为反应物逐渐耗尽。”

Deduce: Use evidence provided in the question to reach a logical conclusion. You must base your answer on the information given, not just general knowledge.

推论：依据题目中提供的证据得出逻辑结论。你的答案必须基于题目信息，而不仅仅是常识。

Example (Chemistry): “An unknown solution turns blue litmus red. Deduce whether it is acidic or alkaline.” Answer: “Acidic, because acids turn blue litmus red.”

化学示例：“未知溶液使蓝色石蕊试纸变红。推论它是酸性还是碱性。”答案：“酸性，因为酸使蓝色石蕊变红。”

11. Identify / Label | 11. 识别 / 标注

Identify: Name the correct structure, substance or organism from a description, diagram or data. For example: “Identify the cell organelle that carries out photosynthesis.” Answer: “Chloroplast.”

识别：从描述、图表或数据中指出正确的结构、物质或生物。例如：“Identify the cell organelle that carries out photosynthesis.”（识别进行光合作用的细胞器。）答案：“叶绿体（chloroplast）。”

Label: Write the correct name on a diagram or drawing. In physics, you may need to label forces with arrows. Make sure the label line points exactly to the correct part.

标注：在图表或示意图上写出正确名称。在物理中，你可能需要用箭头标注力。确保标注线准确指向对应部位。

Common issue: Students often use vague terms such as “gas” when the mark scheme expects “carbon dioxide”. Always be as specific as possible.

常见问题：学生经常使用模糊术语，例如“气体”，但评分标准要求“二氧化碳”。请尽可能具体。

12. Common Mistakes and How to Avoid Them | 12. 常见错误及避免方法

Describing instead of explaining: When asked to explain, add a reason. Use “because” to force yourself to complete the explanation.

用描述代替解释：当题目要求解释时，请加上理由。使用“因为”促使自己补全解释。
Ignoring units in calculations: Write the correct unit for every numerical value. Many students miss the final mark because they write “5” instead of “5 m/s”.

计算中忽略单位：每个数值都要写正确单位。很多学生只写“5”而不写“5 m/s”，因此丢失最后一分。
Overwriting low-mark questions: A 1-mark “State” question does not need two sentences. Extra irrelevant information may confuse the examiner. Keep it concise.

低分题过度展开：1 分的“State”题不需要两句话。无关信息可能让考官困惑。请保持简洁。
Not using data in “describe” questions: If a graph or table is provided, quote exact numbers to show you have read it correctly.

“Describe”题不引用数据：如果题目提供图表或表格，请引用具体数值，以证明你正确读取了信息。
Forgetting to give a conclusion in “evaluate”: After listing pros and cons, you must clearly state your overall judgement.

“Evaluate”题忘记写结论：在列出优缺点后，必须清楚说明你的总体判断。

Conclusion | 结语

Command words are the keys to unlocking marks on IGCSE Edexcel Science papers. Before you start writing, underline the command word and ask yourself: Is this asking me to state, describe, explain, suggest, calculate, compare, evaluate, define, outline, predict, deduce, identify or label? Match your answer type to the command word, and you will immediately improve your accuracy.

命令词是打开 Edexcel IGCSE 科学卷面分数的钥匙。开始动笔之前，先圈出命令词并问自己：这道题要求我“陈述、描述、解释、推测、计算、比较、评估、定义、概述、预测、推论、识别还是标注”？让你的答案类型与命令词匹配，你的准确率就会立即提高。

Published by TutorHao | Science Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）

IGCSE Edexcel Science Command Words Explained | IGCSE Edexcel 科学命令词详解