📚 Year 8 Core Homework Answers: Key Skills and Worked Examples | Year 8 核心作业答案：关键技能与例题解析
This revision guide provides clear, worked answers for common Year 8 core homework questions in mathematics, science, and English. Use it to check your own work, identify where you went wrong, and build stronger problem-solving skills. Always try each question on your own before reading the answer.
本复习指南为 Year 8 数学、科学和英语的常见核心作业题提供了清晰、详细的答案解析。你可以用它来检查自己的作业，找出错误原因，并逐步提升解题能力。请务必在查看答案之前先独立尝试每一道题。
1. How to Use This Answer Guide | 如何使用本答案指南
Start by completing your homework without any help. Once you have written your answers, compare them with the worked solutions in this guide. Mark any questions you got wrong, then re-read the method carefully to understand the correct steps.
首先，独立完成你的家庭作业，不要借助任何帮助。写完答案后，再将你的答案与本指南中的详细解析进行对照。把做错的题目标记出来，然后仔细重读解题步骤，理解正确的做法。
Do not simply copy the final answers. Instead, focus on the process: how each step follows from the previous one. If you still do not understand a question, ask your teacher or a tutor for further explanation.
不要只是抄写最终答案。相反，要把注意力放在解题过程上：每一步是如何从上一步推导出来的。如果仍然不理解某道题，请向老师或辅导员寻求进一步的讲解。
- Complete the work independently first | 先独立完成作业
- Compare your answers step by step | 逐步对照答案
- Write a short note about any mistake you made | 简单记录每一处错误
- Review the same type of question the next day | 第二天复习同类题目
2. Mathematics: Fraction Operations | 数学：分数运算
3/4 = 9/12 and 1/3 = 4/12. Then add the numerators while keeping the denominator the same.
分数在 Year 8 的作业中经常出现。关键是在加减之前先找到公分母。例如，计算 3/4 + 1/3 时，先把两个分数都化成分母为 12 的分数：3/4 = 9/12，1/3 = 4/12。然后分子相加，分母保持不变。
3/4 + 1/3 = 9/12 + 4/12 = 13/12 = 1 1/12
For multiplication, multiply the numerators and denominators directly. For division, flip the second fraction and then multiply. Always simplify your final answer, and change improper fractions to mixed numbers where appropriate.
做乘法时，直接将分子相乘、分母相乘。做除法时，把第二个分数倒过来，再与被除数相乘。最后一定要化简答案，并在合适时将假分数化为带分数。
4 = (2 × 3) / (5 × 4) = 6/20 = 3/10. Example: 5/6 ÷ 2/3 = 5/6 × 3/2 = 15/12 = 5/4 = 1 1/4.
示例：2/5 × 3/4 = (2 × 3) / (5 × 4) = 6/20 = 3/10。示例：5/6 ÷ 2/3 = 5/6 × 3/2 = 15/12 = 5/4 = 1 1/4。
3. Mathematics: Simplifying Algebraic Expressions | 数学：化简代数表达式
To simplify an expression, collect like terms. Like terms have exactly the same letters and powers. For example, 3x and -x are like terms, but 3x and 3x² are not. Add or subtract the coefficients of like terms only.
化简代数表达式时，要合并同类项。同类项是指字母和指数完全相同的项。例如，3x 和 -x 是同类项，但 3x 和 3x² 不是。只需要对同类项的系数进行加减运算。
3x + 2y - x + 5y = (3x - x) + (2y + 5y) = 2x + 7y
nstance, 4(2a + 3) = 8a + 12. Then combine any like terms that appear after the expansion.
去括号时，要用括号外的项乘以括号内的每一项。例如，4(2a + 3) = 8a + 12。去括号之后，如果有同类项，再继续合并。
Example: 2(3x + 1) + 5x - 4 = 6x + 2 + 5x - 4 = 11x - 2.
示例：2(3x + 1) + 5x - 4 = 6x + 2 + 5x - 4 = 11x - 2。
4. Mathematics: Solving Linear Equations | 数学：解一元一次方程
Solving a linear equation means finding the value of the unknown letter. Always aim to get the letter on its own on one side of the equals sign. Use inverse operations: add to undo subtraction, subtract to undo addition, multiply to undo division, and divide to undo multiplication.
解一元一次方程就是求出未知字母的值。我们的目标始终是让未知字母单独位于等号的一边。要使用逆运算：加法的逆运算是减法，减法的逆运算是加法，乘法的逆运算是除法，除法的逆运算是乘法。
2x + 5 = 13
2x = 13 - 5
2x = 8
x = 8 ÷ 2 = 4
= 13, which matches the right-hand side. If both sides are equal, your answer is correct.
一定要把求得的解代回原方程进行检验。当 x = 4 时，左边为 2(4) + 5 = 8 + 5 = 13，与右边相等。如果两边相等，说明你的答案是正确的。
brackets, expand first. Example: 3(x - 2) = 9 becomes 3x - 6 = 9, then 3x = 15, so x = 5.
对于含有括号的方程，先去括号。示例：3(x - 2) = 9 可化为 3x - 6 = 9，然后 3x = 15，因此 x = 5。
5. Science: Cells and Organisation | 科学：细胞与组织
Year 8 homework often asks you to compare animal cells and plant cells. Both have a nucleus, cytoplasm, and cell membrane. Plant cells also have a cell wall, chloroplasts, and a large permanent vacuole, while animal cells do not.
Year 8 的作业经常会让你比较动物细胞和植物细胞。两者都有细胞核、细胞质和细胞膜。植物细胞还具有细胞壁、叶绿体和一个较大的永久液泡，而动物细胞没有这些结构。
| Structure | 结构 | Animal cell | 动物细胞 | Plant cell | 植物细胞 |
| Nucleus | 细胞核 | Yes | 有 | Yes | 有 |
| Cytoplasm | 细胞质 | Yes | 有 | Yes | 有 |
| Cell membrane | 细胞膜 | Yes | 有 | Yes | 有 |
| Cell wall | 细胞壁 | No | 无 | Yes | 有 |
| Chloroplasts | 叶绿体 | No | 无 | Yes | 有 |
| Large vacuole | 大液泡 | No | 无 | Yes | 有 |
The nucleus controls the cell's activities and contains genetic material. The cytoplasm is where most chemical reactions happen. The cell membrane controls what enters and leaves the cell. The cell wall gives plant cells extra support and shape.
细胞核控制细胞的活动，并含有遗传物质。细胞质是大多数化学反应发生的场所。细胞膜控制物质进出细胞。细胞壁为植物细胞提供额外的支撑和固定形状。
6. Science: States of Matter | 科学：物质状态
Matter can exist as a solid, liquid, or gas. In a solid, particles are packed tightly in a regular arrangement and can only vibrate in fixed positions. In a liquid, particles are close together but can slide past each other. In a gas, particles are far apart and move quickly in all directions.
物质可以以固态、液态或气态存在。在固体中，粒子紧密排列成规则的结构，只能在固定的位置上振动。在液体中，粒子彼此靠近，但可以相互滑动。在气体中，粒子相距很远，并且向各个方向快速运动。
The change from solid to liquid is called melting, from liquid to gas is called evaporation or boiling, from gas to liquid is called condensation, and from liquid to solid is called freezing or solidification. These are physical changes, not chemical changes.
由固态变为液态称为熔化，由液态变为气态称为蒸发或沸腾，由气态变为液态称为冷凝，由液态变为固态称为凝固。这些都是物理变化，不是化学变化。
Example answer: If ice is left at room temperature, its particles gain energy and vibrate more strongly. The regular structure breaks down, and the ice melts into liquid water. The particles are still close, but no longer in fixed positions.
示例答案：如果将冰块放在室温下，冰的粒子获得能量，振动加剧。规则的排列结构被打破，冰融化成液态水。此时粒子仍然彼此靠近，但不再处于固定位置。
7. Science: Energy Transfers | 科学：能量转移
Energy cannot be created or destroyed; it can only be transferred from one form to another. This is called the conservation of energy. In many homework questions, you need to describe the energy transfers in a simple system.
能量既不能被创造，也不能被消灭；它只能从一种形式转化为另一种形式。这叫做能量守恒。在许多作业题中，你需要描述一个简单系统中的能量转移过程。
Example: A battery-powered torch. The chemical energy stored in the battery is transferred into electrical energy in the wires. The electrical energy is then transferred into light energy and thermal energy in the bulb. Useful output is light; wasted output is heat.
示例：电池供电的手电筒。电池中储存的化学能转化为导线中的电能。电能接着在灯泡中转化为光能和热能。有用的输出是光，浪费的输出是热。
Chemical energy → Electrical energy → Light energy + Thermal energy
When answering energy transfer questions, always name the starting energy form and the ending energy forms. Use the word 'transferred' rather than 'used up' because energy is never lost, only changed into different types.
回答能量转移问题时，一定要指出起始的能量形式和最终的能量形式。要使用“转移”这个词，而不要说能量被“用光”，因为能量永远不会消失，只会转化为不同的类型。
8. English: Common Grammar Errors | 英语：常见语法错误
Year 8 English homework often asks you to correct grammatical mistakes. One common error is subject-verb agreement. A singular subject takes a singular verb, and a plural subject takes a plural verb. For example, 'He go to school' is incorrect; it should be 'He goes to school.'
Year 8 的英语作业经常要求你改正语法错误。一个常见错误是主谓不一致。单数主语要搭配单数动词，复数主语要搭配复数动词。例如，'He go to school' 是错误的，应改为 'He goes to school.'
Another common mistake is misuse of tenses. If an event happened in the past and is finished, use the past simple. If it happened before another past event, use the past perfect. Always keep the tense consistent within a sentence or short paragraph.
另一个常见错误是时态误用。如果一件事发生在过去并且已经结束，使用一般过去时。如果它发生在另一个过去动作之前，使用过去完成时。在一个句子或一小段话中，要保持时态一致。
Correct the following: 'Yesterday I go to the park and play football with my friends.' The correct version is: 'Yesterday I went to the park and played football with my friends.' Both verbs must be in the past simple.
请改正下面的句子：'Yesterday I go to the park and play football with my friends.' 正确的句子是：'Yesterday I went to the park and played football with my friends.' 两个动词都必须用一般过去时。
9. English: Reading Comprehension Strategies | 英语：阅读理解策略
When answering reading comprehension questions, first skim the passage to get the main idea. Then read the questions carefully and underline the key words. Use those key words to scan the passage and locate the relevant information.
做阅读理解题时，先快速浏览文章，把握大意。然后仔细读题，并在关键词下面划线。利用这些关键词去扫读文章，找到相关信息。
For 'find and copy' questions, write the exact words from the text. For 'explain' questions, use the word 'because' and give evidence from the passage. For 'inference' questions, you must read between the lines and support your answer with a quotation.
对于“找出并抄写”类题目，要写出文章中的原词。对于“解释”类题目，要用“because”这个词，并引用文中的证据。对于“推断”类题目，你需要读懂言外之意，并用引文来支持你的答案。
Example question: Why was the character feeling nervous? Answer: The character was feeling nervous because the text says his hands were shaking and he kept looking at the clock. This shows he was worried about being late.
示例问题：为什么这个角色感到紧张？答案：这个角色感到紧张，因为文中说他的双手在颤抖，并且他不停地看钟。这表明他担心迟到。
10. Common Mistakes and How to Avoid Them | 常见错误及避免方法
Many marks are lost through careless errors rather than a lack of understanding. In mathematics, always write the correct signs and units. Check whether the question asks for cm, m, kg, or another unit, and include it in your final answer.
许多失分是因为粗心错误，而不是因为不理解。在数学中，一定要写对符号和单位。检查题目要求的是厘米、米、千克还是其他单位，并在最终答案中写出来。
In science, avoid vague words such as 'it changes' or 'it gets bigger'. Use precise scientific terms like 'the particles gain kinetic energy' or 'the rate of reaction increases'. Precision shows the examiner that you understand the concept.
在科学中，避免使用模糊的词语，如“它变了”或“它变大了”。要使用准确的科学术语，例如“粒子获得动能”或“反应速率增大”。准确的表达能向阅卷老师展示你真正理解了概念。
- Check your signs and units | 检查符号和单位
- Show every step of your working | 写出每一步解题过程
- Use specific scientific vocabulary | 使用具体的科学词汇
- Re-read the question before writing the final answer | 写最终答案前重读题目
11. Self-Assessment and Reflection | 自我评估与反思
After marking your work, give yourself a score and write one sentence about what you did well. Then write one sentence about what you need to improve. This simple habit helps you turn every homework task into a learning opportunity.
批改完作业后，给自己打一个分数，并写一句自己做得好的地方。再写一句需要改进的地方。这个简单的习惯能帮助你把每一次作业都变成学习的机会。
Keep a small notebook or a digital note for your common mistakes. Before a test, review this list. You will be less likely to repeat the same errors, and your confidence will grow as you see your progress over time.
准备一个小本子或电子笔记，记录你常犯的错误。考试前复习这个清单。这样你就不太可能重复犯同样的错误，而且随着时间推移，看到自己的进步，你的信心也会增强。
Example reflection: 'I solved all fraction addition questions correctly, but I forgot to simplify one answer. Next time I will check for common factors before writing the final answer.'
反思示例：“我所有分数加法题都做对了，但有一个答案忘记化简。下次我会在写出最终答案前检查公因数。”
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