📚 Year 8 OCR Chemistry: Winter Break Intensive Revision Plan | Year 8 OCR 化学：寒假强化复习计划
Winter break offers a unique opportunity to consolidate your Year 8 Chemistry knowledge without the pressure of regular lessons. An intensive, well-structured revision plan can transform those two or three weeks from passive rest into an active launchpad for the next term. This guide provides a day-by-day framework, core topic summaries, and proven study techniques specifically tailored to the OCR Year 8 Chemistry syllabus. You will revisit particles, atoms, the periodic table, chemical reactions, acids, and separation methods while building the confidence to tackle any question.
寒假提供了一个独特的机会，让你在没有日常课堂压力的情况下巩固 Year 8 化学知识。一份密集且结构合理的复习计划，可以将这两三周从被动的休息转变为下学期的主动起跳板。本指南为你量身打造了基于 OCR Year 8 化学考纲的每日框架、核心主题总结和高效学习技巧。你将重新梳理粒子、原子、元素周期表、化学反应、酸和分离方法，同时建立应对任何题目的信心。
1. Why a Winter Revision Plan? | 为什么需要寒假复习计划？
Students often return after the holidays feeling as though they have forgotten half of the previous term’s content. A short daily revision slot prevents this learning loss. For OCR Year 8 Chemistry, concepts like the particle model and symbol equations build directly on one another; gaps in your knowledge now will make future topics such as rates of reaction or quantitative chemistry much harder. A winter plan also reduces pre-exam stress later in the year, giving you the chance to identify and fix weak areas early.
学生常常在假期结束后感觉忘记了上学期一半的内容。每天一小段时间的复习可以防止这种学习流失。对于 OCR Year 8 化学来说，像粒子模型和符号方程式这样的概念是环环相扣的；现在的知识漏洞会让你以后学习反应速率或定量化学时更加吃力。寒假计划还能减轻学年后期考试前的压力，让你有机会及早发现并弥补薄弱环节。
Equally important, a revision plan teaches you how to study independently. Instead of spending an entire day cramming—which is exhausting and ineffective—you learn to break content into manageable chunks, use active recall, and space out repetition. These skills are valuable well beyond Year 8 Chemistry.
同样重要的是，复习计划教会你如何独立学习。它让你学会将内容分解成可管理的小块、运用主动回忆和间隔重复，而不是花一整天来死记硬背——那既累人又低效。这些技能的价值远远超出 Year 8 化学本身。
2. Understanding the OCR Year 8 Syllabus | 解读 OCR Year 8 化学大纲
The OCR Year 8 Chemistry curriculum is designed to build a strong foundation in how matter behaves and changes. Key topic areas usually include: the particle nature of solids, liquids and gases; atoms, elements, compounds and mixtures; the periodic table and patterns in Group 1, Group 7 and Group 0; writing word and simple symbol equations; acids, alkalis and neutralisation; and practical separation techniques such as filtration, distillation and chromatography. Check your school’s specific scheme of work, but most OCR-based courses in Year 8 will cover these six pillars.
OCR Year 8 化学课程旨在为物质的行为与变化打下坚实基础。核心主题通常包括：固体、液体和气体的粒子本质；原子、元素、化合物和混合物；元素周期表及第 1 族、第 7 族和第 0 族的规律；书写文字方程式和简单的符号方程式；酸、碱与中和反应；以及过滤、蒸馏和色谱法等实际分离技术。请核对学校的具体教学计划，但多数基于 OCR 的 Year 8 课程都会覆盖这六大板块。
Before you begin your revision, gather all your resources: class notes, textbooks, any end-of-topic tests, and online platforms recommended by your teacher. Use the syllabus topics as a checklist. Rate your confidence in each area from 1 to 5. This simple self-assessment will help you allocate more time to the topics that need it most, rather than revising the things you already find easy.
在开始复习之前，收集好所有资料：课堂笔记、教材、历次单元测验以及老师推荐的在线平台。将考纲主题作为检查清单，对每个领域的信心程度从 1 到 5 打分。这个简单的自我评估能帮你把更多时间分配给最需要关注的主题，而不是只复习那些你已经掌握得很好的内容。
3. Setting Up Your Revision Timetable | 制定你的复习时间表
A realistic timetable is the backbone of any successful revision plan. Aim for five days of study per week, leaving two full days for rest, family time, and hobbies. Each study day should contain no more than 90 minutes of Chemistry revision, ideally split into two 45-minute sessions with a break in between. For example, a morning session might focus on learning and summarising a topic, while an afternoon session is reserved for practice questions. This prevents burnout and keeps your brain fresh.
一个切实可行的时间表是任何成功复习计划的骨架。目标定为每周学习五天，留出完整的两天用于休息、家庭时光和兴趣爱好。每天化学复习时间不超过 90 分钟，最好分成两个 45 分钟的小块，中间安排休息。例如，上午段可以专注于学习和总结一个主题，下午段则用来做练习题。这样可以防止疲劳，让大脑保持清醒。
| Day | Morning (45 min) | Afternoon (45 min) |
| Monday | Particles and states of matter | Practice questions on states |
| Tuesday | Atoms, elements, compounds | Card sort: element vs compound |
| Thursday | Periodic table and groups | Fill-in table quiz |
| Friday | Chemical equations | Balancing equation drills |
| Saturday | Acids, alkalis, neutralisation | Mini test from memory |
Use a simple paper planner or a digital calendar to block out these sessions. Tick off each session when completed—the visual progress is highly motivating. If you miss a day, do not panic; simply carry on with the next scheduled session. Consistency over the whole break matters far more than a perfect streak.
用简单的纸质计划本或电子日历来锁定这些时间段。每完成一个时段就划掉——肉眼可见的进度会给你极大的动力。如果有一天落下了，不要慌张，继续按计划进行下一个时段。贯穿整个假期的连贯性远比完美的连续打卡更重要。
4. Topic 1: Particles and States of Matter | 主题 1：粒子与物质状态
All matter is made of tiny particles that are constantly moving. In solids, the particles are packed in a regular pattern, held together by strong forces; they vibrate in fixed positions but cannot move past one another. This explains why solids have a definite shape and volume. In liquids, particles are still close together but can slide over each other, so liquids take the shape of their container but keep the same volume. In gases, particles are far apart, moving rapidly in all directions, which is why gases can be compressed and will fill any container completely.
所有物质都由不断运动的微小粒子构成。在固体中，粒子排列成规则的图案，被强大的作用力束缚在一起；它们在固定位置上振动，但无法相互滑过。这解释了为什么固体有确定的形状和体积。在液体中，粒子仍然紧挨着，但可以相互滑动，因此液体能随容器形状而改变，但体积保持不变。在气体中，粒子相距很远，朝各个方向快速运动，这就是气体可以被压缩并充满任何容器的原因。
A common misconception is that particles themselves expand when a substance is heated. What actually happens is that the particles gain kinetic energy, vibrate or move more vigorously, and so the spaces between them increase. This is the key idea behind expansion and contraction. Make sure you can use the particle model to explain familiar observations, such as why a metal lid becomes easier to open after running it under hot water, or why a balloon inflates when placed in a warm room.
一个常见的误解是，物质受热时粒子自身会膨胀。实际发生的情况是，粒子获得动能后振动或运动得更剧烈，于是它们之间的间距增大。这是解释热胀冷缩的核心思路。请务必能够用粒子模型来解释日常生活中所见的现象，例如为什么金属瓶盖用热水冲过后更容易拧开，或者为什么气球放在温暖的房间里会鼓起来。
Key terms to learn: melting, freezing, boiling, condensing, sublimation, diffusion, kinetic energy. Practise drawing neat particle diagrams for all three states, labelling the arrangement and motion clearly.
需要掌握的关键术语：熔化、凝固、沸腾、冷凝、升华、扩散、动能。练习为三种状态绘制整洁的粒子示意图，并清楚地标注出排列方式和运动状态。
5. Topic 2: Atoms, Elements and Compounds | 主题 2：原子、元素与化合物
An element is a substance made of only one type of atom. All the atoms in an element have the same number of protons. For example, a piece of pure iron contains only iron atoms. When two or more different elements chemically combine in fixed proportions, they form a compound. The properties of a compound are entirely different from the elements that make it up: sodium is a highly reactive metal, chlorine is a poisonous green gas, but the compound sodium chloride is the safe, edible salt we sprinkle on food.
元素是由同一种原子组成的物质。一种元素中的所有原子都具有相同数量的质子。例如，一块纯铁只包含铁原子。当两种或两种以上的不同元素以固定的比例发生化学结合时，就形成了化合物。化合物的性质与组成它的元素截然不同：钠是一种反应性极强的金属，氯是有毒的黄绿色气体，但化合物氯化钠却是我们可以撒在食物上的安全食盐。
A mixture, by contrast, contains different substances that are not chemically joined. Mixtures can be separated by physical methods, and each substance keeps its own properties. Air is a mixture of nitrogen, oxygen, carbon dioxide and other gases; sand and iron filings form a mixture, not a compound. Students often struggle to distinguish between an element, a compound and a mixture using particle diagrams. Practise identifying which type of substance is shown when you see circles of different sizes and colours: identical circles alone represent an element; two or more types of circles joined together represent a compound; and circles that are mixed but not joined represent a mixture.
相比之下，混合物含有多种没有发生化学结合的物质。混合物可以通过物理方法分离，且各组分保持自身原有的性质。空气是氮气、氧气、二氧化碳和其他气体的混合物；沙子与铁屑形成的是混合物而非化合物。学生往往难以用粒子示意图区分元素、化合物和混合物。请练习当你看到不同大小和颜色的圆圈时，如何判断所示的物质类型：完全相同的圆圈单独存在代表一种元素；两种或更多种圆圈联结在一起代表一种化合物；而不同圆圈混杂但未联结则代表一种混合物。
6. Topic 3: The Periodic Table | 主题 3：元素周期表
The periodic table organises all known elements by increasing atomic number. In Year 8, OCR students need to be able to identify the positions of metals and non-metals, and name the key groups: Group 1 (alkali metals), Group 7 (halogens) and Group 0 (noble gases). Metals are found on the left and centre; non-metals are on the right. A stepped line typically separates them, with elements like silicon and germanium sitting on the boundary as metalloids or semi-metals.
元素周期表按原子序数递增的顺序排列所有已知元素。在 Year 8， OCR 的学生需要能够辨认金属和非金属的位置，并说出关键族的名称：第 1 族（碱金属）、第 7 族（卤素）和第 0 族（稀有气体）。金属位于左侧和中部，非金属位于右侧。通常有一条阶梯状的斜线将两者分开，硅和锗等元素位于边界上，称为准金属或半金属。
For Group 1, learn the trend: as you go down the group, reactivity increases. Lithium fizzes gently on water, sodium melts into a ball and darts around more vigorously, potassium reacts so fiercely that the hydrogen gas produced ignites with a lilac flame. For Group 7, reactivity decreases down the group: fluorine is the most reactive, iodine the least. Halogens are diatomic molecules, such as F₂, Cl₂, Br₂, I₂. Group 0 elements are monatomic and extremely unreactive because they have a full outer shell of electrons. Remember their uses: helium in balloons, neon in advertising signs, argon in light bulbs.
对于第 1 族，要掌握的规律是：自上而下反应活性增强。锂与水缓慢地发出嘶嘶声，钠融化成小球在水面上剧烈游动，而钾的反应剧烈到产生氢气并立即点燃，形成淡紫色火焰。对于第 7 族，自上而下反应活性减弱：氟最活泼，碘最不活泼。卤素是双原子分子，如 F₂, Cl₂, Br₂, I₂。第 0 族元素是单原子的，极为不活泼，因为它们具有全满的外层电子结构。记住它们的用途：氦气用于气球，氖气用于广告标识，氩气用于灯泡。
Draw a simplified periodic table by hand, labelling the three groups and the metal/non-metal divide. Add a key with a brief description of each group’s properties. This active task cements the layout in your memory far better than simply staring at a textbook.
亲自动手绘制一张简化的周期表，标注出这三个族以及金属与非金属的分界线。附上图例并简短描述各族性质。这个主动完成的任务能将周期表的排布牢牢印在记忆中，远比单纯盯着教材看有效得多。
7. Topic 4: Chemical Reactions and Equations | 主题 4：化学反应与方程式
A chemical reaction always forms one or more new substances. Signs of a reaction include a colour change, a temperature change, bubbles of gas forming, or a precipitate appearing. In Year 8 you will write both word equations and simple symbolic equations. A word equation states the reactants and products using their names: magnesium + oxygen → magnesium oxide. The arrow is read as ‘reacts to form’. The law of conservation of mass means that atoms are never created or destroyed, so the total mass before and after a reaction stays the same.
化学反应总是生成一种或多种新物质。反应发生的迹象包括颜色变化、温度变化、气泡产生或出现沉淀。在 Year 8，你需要学会书写文字方程式和简单的符号方程式。文字方程式用名称来表达反应物和生成物：镁 + 氧气 → 氧化镁。箭头读作“反应生成”。质量守恒定律告诉我们，原子永远不会凭空产生或消失，因此反应前后的总质量保持不变。
Writing a correct symbol equation is a skill that takes practice. Start by writing the word equation, then replace each name with its chemical formula. For example, hydrogen + oxygen → water becomes H₂ + O₂ → H₂O. But this equation is unbalanced: on the left there are two oxygen atoms, on the right only one. To balance it, we must place a 2 in front of H₂O and a 2 in front of H₂: 2H₂ + O₂ → 2H₂O. Never change the small subscript numbers inside a formula; only add large coefficients in front.
书写正确的符号方程式是一项需要练习的技能。先写出文字方程式，然后用化学式替换每个名称。例如，氢气 + 氧气 → 水变成 H₂ + O₂ → H₂O。但这个方程式是不平衡的：左边有两个氧原子，右边只有一个。为了配平，我们必须在 H₂O 前放系数 2，在 H₂ 前也放系数 2：2H₂ + O₂ → 2H₂O。千万不要更改化学式里的小下标数字，只能在前方添加大的系数。
Practise balancing a set of five equations each day. Start with simple ones: Na + Cl₂ → NaCl, then progress to: CH₄ + O₂ → CO₂ + H₂O. As you get quicker, you will start to recognise patterns and common products, which makes tackling unfamiliar reactions much less intimidating.
每天练习配平五道方程式。从简单的 Na + Cl₂ → NaCl 开始，然后逐步提升到 CH₄ + O₂ → CO₂ + H₂O。随着速度加快，你会开始识别出规律和常见产物，这样在面对陌生反应时就不那么容易感到畏惧了。
8. Topic 5: Acids and Alkalis | 主题 5：酸与碱
Acids are substances with a pH lower than 7. They taste sour (though you should never taste chemicals in the lab) and contain hydrogen ions, H⁺, when dissolved in water. Common laboratory acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃). Alkalis are soluble bases with a pH greater than 7; they produce hydroxide ions, OH⁻, in water. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) are typical examples. A neutral solution has a pH of exactly 7, like pure water.
酸是 pH 值低于 7 的物质。它们尝起来有酸味（但绝不能在实验室里品尝化学品），溶于水时含有氢离子 H⁺。常见的实验室用酸包括盐酸 (HCl)、硫酸 (H₂SO₄) 和硝酸 (HNO₃)。碱是可溶性的氢氧根离子 OH⁻ 提供者，pH 值大于 7；氢氧化钠 (NaOH) 和氢氧化钾 (KOH) 是典型例子。中性溶液的 pH 值恰好为 7，比如纯水。
The reaction between an acid and an alkali is called neutralisation. In every neutralisation, hydrogen ions react with hydroxide ions to form water: H⁺ + OH⁻ → H₂O. The other product is a salt; the name of the salt comes from the acid and the metal in the base. Hydrochloric acid produces chlorides, sulfuric acid produces sulfates, nitric acid produces nitrates. For example, hydrochloric acid + sodium hydroxide → sodium chloride + water. Use the pH scale and universal indicator colours to determine whether an unknown solution is acidic, alkaline or neutral. Learn the colours: red (strong acid), orange, yellow, green (neutral), blue, purple (strong alkali).
酸与碱之间的反应称为中和反应。在每一个中和反应中，氢离子与氢氧根离子反应生成水：H⁺ + OH⁻ → H₂O。另一种产物是盐；盐的名称来自酸和碱中的金属。盐酸产生氯化物，硫酸产生硫酸盐，硝酸产生硝酸盐。例如，盐酸 + 氢氧化钠 → 氯化钠 + 水。运用 pH 标度和通用指示剂的颜色来判断未知溶液是酸性、碱性还是中性。牢记颜色：红色（强酸）、橙色、黄色、绿色（中性）、蓝色、紫色（强碱）。
9. Topic 6: Separation Techniques | 主题 6：分离技术
Mixtures can be separated into their components using physical methods that exploit differences in their physical properties. Filtration is used to separate an insoluble solid from a liquid, such as sand from salty water. The mixture is poured through filter paper in a funnel; the solid residue stays on the paper while the filtrate passes through. Crystallisation can then recover a dissolved solid from the filtrate by gently heating to evaporate the solvent, leaving crystals behind.
混合物可以通过利用各组分物理性质差异的物理方法进行分离。过滤用于分离不溶性固体和液体，例如将沙子从盐水中分离出来。将混合物倒入漏斗中的滤纸；固体残渣留在滤纸上，而滤液则穿过滤纸。之后可以通过结晶从滤液中回收溶解的固体，方法是温和加热蒸发溶剂，留下晶体。
Distillation separates a liquid from a solution or from a mixture of liquids with different boiling points. In simple distillation, the solution is heated, the liquid with the lower boiling point evaporates first, and its vapour is then cooled and condensed back into a liquid in the condenser, collected as the distillate. Chromatography separates dissolved substances, such as the different dyes in ink, based on their different solubilities and attraction to the paper. The more soluble a substance, the further it travels up the paper.
蒸馏用于将液体从溶液中分离出来，或从具有不同沸点的液体混合物中分离出液体。在简单蒸馏中，加热溶液，沸点较低的液体首先蒸发，其蒸气随后在冷凝管中被冷却并凝结回液态，作为蒸馏液收集起来。色谱法根据溶解物质的不同溶解度和对纸张的吸附力来分离它们，例如分离墨水中的不同染料。一种物质的溶解度越大，它在纸上移动得越远。
Be ready to describe a full method for each technique in an exam question, including the names of the apparatus: conical flask, filter funnel, beaker, evaporating dish, condenser, thermometer, chromatography paper, solvent front. Draw labelled diagrams and always mention safety precautions such as wearing goggles and not pointing the open end of a test tube at anyone.
准备好在试题中完整描述每种分离技术的方法，包括仪器名称：锥形瓶、漏斗、烧杯、蒸发皿、冷凝管、温度计、色谱纸、溶剂前沿。画出带标签的示意图，并务必提及安全注意事项，例如佩戴护目镜以及不要将试管的开口端朝向任何人。
10. Practice and Past Paper Techniques | 练习与真题技巧
Knowledge alone is not enough; you must apply it under exam-style conditions. Begin with end-of-topic questions from your textbook or from OCR-specific worksheets. Answer them fully, without looking at notes first. Then use a mark scheme to mark your work—be strict with yourself. Pay close attention to the specific wording that the mark scheme demands. For example, ‘particles gain kinetic energy’ is often required instead of ‘particles move faster’.
仅有知识是不够的，你必须能在考题型条件下运用它们。从教材或 OCR 专项练习题中的单元后问题开始做起。先不看笔记，完整作答。然后用评分标准来批改——对自己严格要求。尤其注意评分标准所要求的特定措辞。例如，通常要求写出“粒子获得动能”而不是“粒子运动得更快”。
After you have completed a few topic tests, find a past paper or a specimen paper. Time yourself strictly. In year 8, a typical paper might be 45–60 minutes. Do not stop halfway; practising full papers builds your mental stamina. After marking, write a ‘corrections log’: for every mark lost, write what the correct answer was and why you lost the mark. Was it a knowledge gap, a misreading of the question, a careless mistake, or a lack of detail? This analysis will show you exactly where to focus your remaining revision time.
在完成几份单元测试后，找一份往年试卷或样卷。严格计时。Year 8 的典型试卷时长可能在 45-60 分钟。不要半途而废；练习完整的试卷能锻炼你的脑力耐力。批改后，制作一份“改错日志”： 为每一处失分记下正确答案是什么以及为何失分。是知识盲区、误读题目、粗心错误还是答案不够详细？这一分析会准确地告诉你，剩余的复习时间应该集中在哪里。
11. Common Mistakes and How to Avoid Them | 常见错误及如何避免
One of the most frequent errors is confusing atoms, molecules and compounds. Remember: an atom is a single particle of an element; a molecule is two or more atoms chemically joined; a compound is a substance made of at least two different types of atoms. Thus, O₂ is a molecule but not a compound, while CO₂ is both a molecule and a compound.
最常见的错误之一是混淆原子、分子和化合物。记住：原子是元素的一种单个粒子；分子是两个或更多个原子通过化学键结合在一起的粒子；化合物是由至少两种不同种类的原子组成的物质。因此，O₂ 是分子但不是化合物，而 CO₂ 既是分子也是化合物。
Another common pitfall is writing unbalanced equations. Always count the number of each type of atom on both sides after you think you have balanced an equation. Use a table if it helps: list each element, tally reactants, tally products, then adjust coefficients. Also, remember that you cannot change the small numbers in formulas—H₂O must stay as two hydrogens and one oxygen; you cannot change it to H₃O to balance another side.
另一个常见陷阱是书写未配平方程式。在你认为已配平方程式之后，务必清点两边每种原子的数目。如果有助于配平，可以使用表格：列出每种元素，计算反应物侧原子数，计算生成物侧原子数，然后调整系数。同时要记住，你绝不能改变化学式中的小下标数字——H₂O 必须是两个氢一个氧，不能为了配平另一边而改成 H₃O。
In extended questions, students often forget to use the particle model to explain observations. Even if the question does not explicitly say ‘use the particle model’, it is good practice to do so when explaining changes of state, gas pressure, or expansion. Using words like ‘particles are arranged in a regular pattern’ or ‘particles slide past each other’ shows deeper understanding and almost always gains the mark.
在阐述题中，学生经常忘记用粒子模型来解释观察到的现象。即使题目没有明确说“用粒子模型解释”，在解释物态变化、气体压强或热膨胀时，养成使用粒子模型的习惯也是很好的做法。使用“粒子排列成规则图案”或“粒子相互滑动”这类表述能展示更深层次的理解，而且几乎总能得分。
12. Final Review and Confidence Building | 最终复习与信心建立
In the last few days of your winter break, pull all the topics together. One effective technique is to create a single A3 summary poster for the entire Year 8 Chemistry course. Include key diagrams, equations, definitions and one worked example per topic. This forces you to condense information and spot connections between different topics—for example, how the reactivity of Group 1 metals relates to their electron structure and their reactions with water.
在寒假的最后几天，把所有主题串联起来。一个有效的技巧是制作一张涵盖整个 Year 8 化学课程的 A3 总结海报。内容包括关键图示、方程式、定义，并为每个主题附上一个完整的解题示例。这迫使你压缩信息，并找出不同主题之间的联系——例如，第 1 族金属的反应活性与其电子结构和它们与水的反应是如何联系在一起的。
Teach a family member or a friend one of the topics from memory. Explaining concepts aloud, without consulting notes, is one of the most powerful ways to check your own understanding. If you stumble over a section, make a note and review it straight after. Also, ensure your well-being during revision: sleep 8–9 hours a night, drink water, eat balanced meals, and get outside for some fresh air and movement every day. A healthy body supports a focused mind.
凭记忆向一位家庭成员或朋友讲解其中某个主题。不翻阅笔记，大声解释概念，这是检验自己理解程度最有力的方法之一。如果在某个部分卡住了，记下来并立刻重温。同时，在复习期间保持良好的身心状态：每晚睡足 8–9 小时，补充足够水分，均衡饮食，并且每天到户外呼吸新鲜空气、活动身体。健康的身体才能支撑专注的头脑。
Finally, approach the new term with the quiet confidence that you have put in the work. You do not need to be perfect; you just need to be better than you were at the end of last term. Remember that Chemistry is a story about how the entire material world works—from a single atom to the stars. Your winter revision is the chapter where that story truly begins to make sense.
最后，以一份沉静的自信迎接新学期：你已经付出了努力。你不需要做到完美无缺，只需要比上学期末的自己更进一步。请记住，化学是一个关于整个物质世界——从单个原子到星体——如何运作的故事。你寒假的复习便是这个故事真正开始变得清晰透彻的篇章。
Published by TutorHao | 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Cancel reply