Cambridge Lower Secondary Science Workbook 9: Core Topics and Exam Skills | 剑桥初中科学练习册 9：核心主题与考试技巧

📚 Cambridge Lower Secondary Science Workbook 9: Core Topics and Exam Skills | 剑桥初中科学练习册 9：核心主题与考试技巧

Cambridge Lower Secondary Science Workbook 9 consolidates Stage 9 learning through structured practice in biology, chemistry and physics. It focuses on key knowledge, experimental skills, data handling and the use of scientific vocabulary in short and extended answers.

剑桥初中科学练习册 9 通过生物、化学和物理的结构化练习，巩固 Stage 9 的学习内容。它重点关注核心知识、实验技能、数据处理以及在简短和拓展答案中使用科学词汇。

1. Photosynthesis and Plant Transport | 光合作用与植物运输

Photosynthesis is the process by which green plants make glucose using light energy, carbon dioxide and water. Chlorophyll in chloroplasts absorbs light, and oxygen is released as a by-product.

光合作用是绿色植物利用光能、二氧化碳和水制造葡萄糖的过程。叶绿体中的叶绿素吸收光能，并释放氧气作为副产物。

carbon dioxide + water → glucose + oxygen

Workbook 9 questions often ask you to test for starch or explain why a leaf must be destarched before an experiment. A plant kept in the dark for 24 hours uses up its stored starch, so any starch found after the experiment must have been produced during the test period.

练习册 9 的题目经常要求你检验淀粉，或解释为什么实验前必须对叶片进行饥饿处理。将植物放在黑暗中 24 小时会消耗其储存的淀粉，因此实验后检测到的任何淀粉一定是在测试期间产生的。

Xylem transports water and mineral ions from the roots to the leaves, while phloem transports glucose and other nutrients around the plant. Transpiration is the loss of water vapour from leaves, which pulls more water up the xylem.

木质部将水和矿物质离子从根部运输到叶片，而韧皮部将葡萄糖和其他养分运输到植物全身。蒸腾作用是叶片散失水蒸气的过程，它拉动更多水分沿木质部上升。

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2. Inheritance and Variation | 遗传与变异

DNA carries genetic information in the form of genes located on chromosomes. Sexual reproduction produces variation because offspring inherit half their alleles from each parent, so each individual has a unique combination of genes.

DNA 以基因的形式携带遗传信息，基因位于染色体上。有性生殖产生变异，因为后代从父母双方各继承一半等位基因，因此每个个体都有独特的基因组合。

A dominant allele only needs one copy to be expressed, while a recessive allele needs two copies. For example, if brown eye colour is dominant (B) and blue eye colour is recessive (b), a person with Bb will have brown eyes.

显性等位基因只需一个拷贝即可表现，而隐性等位基因需要两个拷贝才能表现。例如，如果棕色眼色为显性 (B)，蓝色眼色为隐性 (b)，那么基因型为 Bb 的人会有棕色眼睛。

Continuous variation, such as height or hand span, shows a range of values and is often influenced by both genes and environment. Discontinuous variation, such as blood group or tongue rolling, falls into clearly separate categories.

连续变异（如身高或手掌宽度）表现为一个数值范围，通常受基因和环境共同影响。不连续变异（如血型或卷舌）则分为明显不同的类别。

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3. The Periodic Table: Groups and Periods | 元素周期表：族与周期

The periodic table arranges elements in order of increasing atomic number. A group is a vertical column, and elements in the same group have similar chemical properties because they have the same number of outer-shell electrons.

元素周期表按原子序数递增排列。族是纵列，同一族的元素化学性质相似，因为它们具有相同数目的最外层电子。

Group 1 metals are very reactive with water, producing hydrogen gas and a metal hydroxide. Group 7 halogens become more reactive as you go up the group, while Group 8 noble gases are unreactive because they have a full outer shell.

第 1 族金属与水反应非常剧烈，生成氢气和金属氢氧化物。第 7 族卤素越往上越活泼，而第 8 族稀有气体不活泼，因为它们具有满的最外层电子结构。

Metals are found on the left side and centre of the periodic table, while non-metals are mainly on the right. Elements in the same period have the same number of electron shells.

金属位于周期表的左侧和中间，非金属主要位于右侧。同一周期的元素具有相同数目的电子层。

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4. Reactivity Series and Displacement | 活动性顺序与置换反应

The reactivity series places metals in order of their tendency to form positive ions. Potassium and sodium are at the top; copper, silver and gold are at the bottom.

活动性顺序将金属按照形成阳离子的倾向排列。钾和钠在最上面；铜、银和金在底部。

K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Ag > Au

A more reactive metal can displace a less reactive metal from its salt solution. For example, zinc displaces copper from copper(II) sulfate solution because zinc is higher in the reactivity series.

较活泼的金属能从较不活泼金属的盐溶液中将其置换出来。例如，锌能从硫酸铜溶液中置换出铜，因为锌在活动性顺序中位置较高。

Zn + CuSO₄ → ZnSO₄ + Cu

Workbook questions often include colour changes, such as the blue copper(II) sulfate solution losing colour as copper metal forms. Always link the observation to the displacement reaction.

练习册题目经常涉及颜色变化，例如蓝色的硫酸铜溶液随着铜金属的生成而褪色。始终要将观察到的现象与置换反应联系起来。

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5. Acids, Bases and pH | 酸、碱与 pH

Acids have a pH below 7 and release hydrogen ions (H⁺) in solution. Bases have a pH above 7, and alkalis are soluble bases that release hydroxide ions (OH⁻).

酸的 pH 值小于 7，在溶液中释放氢离子 (H⁺)。碱的 pH 值大于 7，而碱溶液是可溶性碱，释放氢氧根离子 (OH⁻)。

Neutralisation occurs when an acid reacts with a base to form a salt and water, for example HCl + NaOH → NaCl + H₂O. This reaction can be followed using an indicator or a pH probe.

中和反应是酸与碱反应生成盐和水，例如 HCl + NaOH → NaCl + H₂O。该反应可以用指示剂或 pH 探头追踪。

Substance 物质	pH	Type 类型
Hydrochloric acid 盐酸	1-2	Strong acid 强酸
Pure water 纯水	7	Neutral 中性
Sodium hydroxide 氢氧化钠	13-14	Strong alkali 强碱

Universal indicator shows a range of colours from red in strong acids to purple in strong alkalis. Litmus paper only tells you whether a solution is acidic or alkaline, not the exact pH.

通用指示剂在强酸中呈红色，在强碱中呈紫色。石蕊试纸只能判断溶液是酸性还是碱性，不能给出具体的 pH 值。

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6. Density, Forces and Moments | 密度、力与力矩

Density is mass per unit volume. The formula is ρ = m ÷ V, where m is mass and V is volume. A solid that is denser than a fluid will sink, while a less dense solid will float.

密度是单位体积的质量。公式为 ρ = m ÷ V，其中 m 是质量，V 是体积。密度大于流体的固体会下沉，密度较小的固体则会上浮。

Forces can be contact forces, such as friction and air resistance, or non-contact forces, such as gravity and magnetism. Free-body diagrams use arrows to show the size and direction of forces.

力可以是接触力，如摩擦力和空气阻力，也可以是非接触力，如引力和磁力。受力图用箭头表示力的大小和方向。

Moments are turning effects of forces. A moment equals force multiplied by perpendicular distance from the pivot: M = F × d. For a balanced object, clockwise moments equal anticlockwise moments.

力矩是力的转动效应。力矩等于力乘以到支点的垂直距离：M = F × d。对于平衡的物体，顺时针力矩等于逆时针力矩。

Workbook questions may also ask about pressure, where pressure = force ÷ area. A sharp knife exerts high pressure because the same force acts over a small area.

练习册题目也可能考查压强，其中压强 = 力 ÷ 面积。锋利的刀之所以压强大，是因为相同的力作用在较小的面积上。

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7. Energy Stores and Transfers | 能量储存与转移

Energy can be stored as kinetic, gravitational potential, chemical, elastic, thermal, nuclear, electrostatic and magnetic energy. It is transferred by heating, waves, electric current or mechanical work.

能量可以储存为动能、重力势能、化学能、弹性势能、热能、核能、静电和磁能。它通过加热、波、电流或机械做功传递。

In any closed system, total energy is conserved; energy is not created

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