📚 A Balanced Diet Mark Scheme | 均衡膳食评分标准解析
CIE KS3 Science mark schemes reward precise scientific vocabulary, not general 'healthy eating' statements. To score full marks on a balanced diet question, you need to name nutrients, link them to their functions, and explain why proportions matter. This article shows what examiners look for and how to write mark-scheme style answers.
CIE KS3 科学评分标准奖励准确的专业词汇，而不是笼统的“健康饮食”说法。要在均衡膳食题上拿满分，你需要说出营养素名称、把它们与功能联系起来，并解释为什么比例很重要。本文将展示考官关注什么，以及如何写出符合评分标准的答案。
1. What the Mark Scheme Expects | 评分标准的基本要求
A balanced diet means eating a variety of foods in the right amounts to supply all essential nutrients, including water and dietary fibre. In CIE mark schemes, the definition mark is usually given for two ideas: 'all nutrients' or 'all food groups' and 'correct proportions' or 'right amounts'. Simply saying 'eating healthy food' does not earn the mark.
均衡膳食是指摄入多种食物且数量适当，以提供所有必需营养素，包括水和膳食纤维。在 CIE 评分标准中，定义分通常给两个要点：“所有营养素（或所有食物类别）”和“比例正确（或数量适当）”。只说“吃得健康”不能得分。
Examiners accept either nutrient names or food groups, but avoid mixing them in a confused way. For example, 'a balanced diet contains carbohydrate, protein, fat, vitamins, minerals, fibre and water in the correct amounts' is a full-mark answer. You do not need to list every example food, but you do need to show that proportions matter.
考官接受营养素名称或食物类别，但不要混乱地混用。例如“均衡膳食含有碳水化合物、蛋白质、脂肪、维生素、矿物质、膳食纤维和水，并且数量正确”就是满分答案。你不需要列出所有示例食物，但必须体现“比例”这一要点。
- Accept: 'all nutrients in the right proportions' — 接受：“所有营养素比例正确”
- Accept: 'all food groups in the correct amounts' — 接受：“所有食物类别数量正确”
- Reject: 'eating good food' or 'not eating junk food' — 不接受：“吃好食物”或“不吃垃圾食品”
2. The Seven Nutrient Groups | 七类营养素
For KS3, CIE expects you to know seven components of a balanced diet: carbohydrates, proteins, fats (lipids), vitamins, minerals, dietary fibre, and water. Some mark schemes use 'fat' rather than 'lipid'; either is accepted, but 'lipids' is the more scientific term. Listing all seven correctly is a quick way to gain marks.
在 KS3 阶段，CIE 要求你掌握均衡膳食的七类成分：碳水化合物、蛋白质、脂肪（脂类）、维生素、矿物质、膳食纤维和水。有些评分标准用“fat”而不是“lipid”；两者都可以接受，但“lipids”是更科学的术语。正确列出全部七项是快速拿分的方法。
| Nutrient 营养素 | Function 功能 | Mark-scheme phrase 评分关键词 |
|---|---|---|
| Carbohydrate 碳水化合物 | Main source of energy 主要能量来源 | energy 能量 |
| Protein 蛋白质 | Growth and repair 生长与修复 | growth / repair 生长 / 修复 |
| Fat 脂肪 | Energy store; insulation 能量储存；保温 | stored energy / insulation 储存能量 / 保温 |
| Vitamins 维生素 | Small amounts for health 少量保健 | prevent deficiency disease 预防缺乏症 |
| Minerals 矿物质 | Small amounts for health 少量保健 | bones, blood, etc. 骨骼、血液等 |
| Dietary fibre 膳食纤维 | Keeps gut moving 促进肠道蠕动 | prevents constipation 预防便秘 |
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