📚 Year 10 Cambridge Science: Unit Test Mock Paper Walkthrough | 剑桥十年级科学：单元测试模拟卷解析
Welcome to this detailed walkthrough of a Year 10 Cambridge Science mock unit test covering biology, chemistry and physics topics. We will break down each question, explain the correct answers and highlight common pitfalls, so you can strengthen your revision and exam technique.
欢迎来到本次十年级剑桥科学单元测试模拟卷的详细解析。我们将逐一拆解每道生物、化学和物理题目，讲解正确答案并指出常见错误，帮助大家巩固复习并提升答题技巧。
1. Q1: Identifying the Photosynthetic Organelle | 识别光合作用细胞器
The question asks which organelle is responsible for photosynthesis. The correct answer is 'C. Chloroplast'. Chloroplasts contain the green pigment chlorophyll, which captures light energy to convert carbon dioxide and water into glucose. Mitochondria are the site of respiration, the nucleus stores genetic material, and ribosomes synthesise proteins – none of these carry out photosynthesis.
题目问哪一个细胞器负责光合作用，正确答案是“C. 叶绿体”。叶绿体含有绿色色素叶绿素，能捕获光能，将二氧化碳和水转化为葡萄糖。线粒体是呼吸作用的场所，细胞核储存遗传物质，核糖体合成蛋白质——这些结构都不进行光合作用。
2. Q2: Choosing the Correct Photosynthesis Equation | 选择正确的光合作用方程式
Many students lose marks by picking an unbalanced equation. The balanced symbol equation for photosynthesis is shown below. Remember that six molecules of carbon dioxide and six of water yield one glucose molecule and six oxygen molecules, in the presence of light and chlorophyll.
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
很多学生因为选错未配平的方程式而丢分。光合作用的配平方程式如下。要记住，在光照和叶绿素的作用下，六分子二氧化碳和六分子水反应生成一分子葡萄糖和六分子氧气。
3. Q3: Adaptations of the Small Intestine | 小肠的适应性特征
The small intestine is adapted for efficient absorption of digested food. Its inner wall is folded into finger-like villi, which hugely increase the surface area. The epithelium of each villus is only one cell thick, giving a short diffusion distance. A dense network of blood capillaries quickly transports absorbed nutrients away, maintaining a steep concentration gradient. Lacteals inside villi absorb fatty acids and glycerol into the lymphatic system.
小肠在结构上特别适应于消化产物的高效吸收。其内壁折叠成指状的绒毛，极大地增加了表面积。每个绒毛的上皮只有单层细胞厚，扩散距离很短。密集的毛细血管网能迅速将吸收的营养物质运走，从而维持了较陡的浓度梯度。绒毛内部的乳糜管则将脂肪酸和甘油吸收进入淋巴系统。
4. Q4: Starch Test Procedure and Outcome | 淀粉检验步骤与结果
To test for starch, add a few drops of iodine solution to the food sample. If starch is present, the iodine solution changes colour from yellow-brown to a distinctive blue-black. This colour change is the positive result. A control using water instead of food sample should show no colour change.
检验淀粉的方法是在食物样本上滴加几滴碘液。如果存在淀粉，碘液会由黄褐色变为特殊的蓝黑色。这一颜色变化即为阳性结果。以水代替食物样本进行对照测试，应不发生颜色变化。
5. Q5: Mass Number Calculation | 质量数计算
has 11 protons and 12 neutrons, so the mass number is 11 + 12 = 23. The correct choice is C.
Mass number = protons + neutrons = 23
原子可以用原子序数（质子数）和质量数来描述。质量数等于质子数加中子数的总和。题目中原子有 11 个质子和 12 个中子，因此质量数为 11 + 12 = 23，正确选项是 C。
6. Q6: Increasing Reaction Rate | 提高反应速率
In the reaction between magnesium and hydrochloric acid, the rate can be increased by grinding the magnesium into a powder. This increases the solid's surface area, allowing more frequent collisions between reactant particles. Lowering temperature reduces particle energy, lowering concentration decreases the number of particles per volume, and using a larger volume of acid (at the same concentration) does not change the collision frequency – only the total amount available. The answer is C.
在镁与盐酸的反应中，将镁条研磨成粉末可以提高反应速率。这样做增大了固体的表面积，使反应物粒子之间发生更频繁的碰撞。降低温度会减小粒子能量，降低浓度会减少单位体积内的粒子数目，而使用更大量但浓度相同的酸并不能改变碰撞频率——只是可用的物质量更多而已。因此答案选 C。
7. Q7: Motion: Acceleration Calculation | 运动：加速度计算
) and reaching 20 m/s in 5 seconds, we use the equation below. The acceleration is 4 m/s².
a = (v − u) / t = (20 m/s − 0) / 5 s = 4 m/s²
加速度定义为速度变化的快慢。物体从静止（初速度 u = 0 m/s）开始，5 秒内加速到 20 m/s，利用公式计算得加速度为 4 m/s²。
8. Q8: Applying Ohm's Law and Series Resistance | 应用欧姆定律与串联电阻
Ohm' e total resistance becomes 4 Ω + 4 Ω = 8 Ω. The new current is 12 V ÷ 8 Ω = 1.5 A. Always show the steps clearly.
I₁ = V / R = 12 / 4 = 3 A
R(total) = 4 + 4 = 8 Ω
I₂ = 12 / 8 = 1.5 A
欧姆定律公式 I = V / R。12 V 电池连接单个 4 Ω 电阻，电流为 3 A。当串联第二个 4 Ω 电阻时，总电阻变为 8 Ω，此时电流降为 1.5 A。作答时要写出清晰的步骤。
9. Q9: Reading a Heating Curve | 解读加热曲线
A typical heating curve for a pure solid shows a steady temperature rise until the melting point, where a flat region appears while the solid turns into liquid. The temperature stays constant because the energy absorbed is used to overcome intermolecular forces (latent heat of fusion). After melting, the temperature rises again until boiling, giving a second flat region for the liquid-to-gas transition. Students should label the melting point as the first flat segment and boiling point as the second.
典型纯固体的加热曲线先稳定升温，到达熔点时出现一个平台，此时固体正在熔化为液体。温度保持不变是因为吸收的能量用于克服分子间作用力（熔化潜热）。熔化完成后温度再次上升，到达沸点时出现第二个平台，代表液体变为气体。学生应标记第一个平台段为熔点，第二个为沸点。
10. Q10: Designing a Rate Experiment | 设计反应速率实验
To investigate how temperature affects the rate of reaction between sodium thiosulfate and hydrochloric acid, use the ‘disappearing cross’ method. The independent variable is temperature (thermostatic water bath at 20°C, 30°C, 40°C, 50°C, 60°C). The dependent variable is the time taken for the cross to disappear when viewed from above. Control variables: concentration and volume of both solutions, same size of conical flask, same cross. Repeat each temperature three times, calculate mean times, and optionally calculate rate as 1/time. Plot a graph of rate against temperature. Wear safety goggles and handle warm apparatus with care.
研究温度对硫代硫酸钠与盐酸反应速率的影响，可使用“消失的十字”法。自变量为温度（用恒温水浴控制在 20°C、30°C、40°C、50°C、60°C）。因变量为从上方观察时十字消失所需的时间。控制变量有：两种溶液的浓度和体积、锥形瓶大小相同、十字标记相同。每个温度重复实验三次，计算平均时间，也可用 1/时间表示速率。绘制速率－温度图像。注意佩戴护目镜并小心处理热仪器。
11. Q11: Carbon Cycle and Fossil Fuels | 碳循环与化石燃料
Burning fossil fuels releases carbon dioxide that had been locked underground for millions of years into the atmosphere. This disrupts the natural carbon cycle by adding a large amount of extra CO₂. The enhanced greenhouse effect traps more heat, leading to global warming and climate change. Deforestation also reduces the number of trees available to absorb CO₂ through photosynthesis, making the imbalance worse. Essays can link these ideas to acid rain and environmental policies.
燃烧化石燃料会将深埋地底数百万年的碳以二氧化碳的形式大量释放到大气中，打破了自然的碳循环。增强的温室效应困住更多热量，导致全球变暖和气候变化。森林砍伐还减少了通过光合作用吸收二氧化碳的树木数量，使失衡更严重。论述时可将这些概念与酸雨及环保政策联系起来。
12. Top Tips for Science Exams | 科学考试高分技巧
Always read the question carefully and underline key command words. Use scientific terminology precisely – say ‘increases surface area’ rather than ‘makes it smaller’. Show all workings in calculations and include units. In experimental design questions, mention control variables clearly. Manage your time: do not spend too long on a single 1‑mark question. If you finish early, check for careless mistakes like missing units or unbalanced equations.
务必仔细读题并在关键指令词下划线。准确使用科学术语——例如说“增大表面积”，而不要说“弄碎它”。计算题要展示全部步骤并带单位。实验设计题中要清楚说明控制变量。合理分配时间，不要在一道1分题上耗太久。提前完成时要检查是否因为粗心而漏掉了单位或方程式未配平等错误。
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