📚 Year 7 CCEA Chemistry: Mock Unit Test Walkthrough | Year 7 CCEA 化学：单元测试模拟卷解析
Welcome to our detailed walkthrough of a Year 7 CCEA Chemistry mock unit test. This resource breaks down typical exam-style questions, providing clear explanations of the correct answers and the scientific principles behind them. Use these worked examples to strengthen your understanding of particle theory, elements and compounds, separation techniques, and acids and alkalis – all core topics in the Key Stage 3 curriculum for Northern Ireland.
欢迎阅读 Year 7 CCEA 化学单元测试模拟卷的详细解析。本文拆解了典型的考试类题目，清楚地解释正确答案以及其背后的科学原理。通过这些例题，你可以加深对粒子理论、元素与化合物、分离技术以及酸和碱的理解——这些全是北爱尔兰关键阶段 3 课程的核心主题。
1. The Particle Model of Matter | 物质的粒子模型
Question: Draw and describe how the particles are arranged in a solid. Use the particle model to explain why a solid cannot be compressed.
问题：画出并描述固体中粒子的排列方式。利用粒子模型解释为什么固体不能被压缩。
In a solid, particles are held closely together in a regular, repeating pattern, often called a lattice.
在固体中，粒子紧密地排列成规则、重复的图案，常被称为晶格。
There are almost no empty spaces between the particles, so they cannot be pushed any closer.
粒子之间几乎没有空隙，因此它们无法被进一步挤压靠近。
This is why solids have a fixed volume and cannot be compressed – the strong forces of attraction keep the particles locked in position.
这就是为什么固体有固定的体积且不可压缩——强大的吸引力将粒子固定在原位。
2. Particle Arrangements in Liquids and Gases | 液体与气体中的粒子排列
Question: Compare the movement and spacing of particles in a liquid with those in a gas.
问题：比较液体和气体中粒子的运动与间距。
In a liquid, particles are still close together but they are arranged randomly, not in a fixed lattice.
在液体中，粒子仍然彼此靠近，但它们排列随机，没有固定的晶格。
They can slide and move past one another, which allows a liquid to flow and take the shape of its container.
它们可以相互滑动和移动，这使得液体能够流动并呈现容器的形状。
In a gas, particles are far apart and move rapidly in all directions, with very weak forces between them.
在气体中，粒子彼此相距很远，朝各个方向快速运动，粒子间的作用力非常弱。
This means a gas has no fixed shape or volume and can be compressed easily because there is lots of space between the particles.
这意味着气体没有固定的形状或体积，并且容易被压缩，因为粒子之间有大量的空间。
3. Changes of State and Energy | 状态变化与能量
Question: Explain what happens to the particles when ice melts into water. Why does the temperature stay at 0 °C while melting occurs?
问题：解释当冰融化成水时粒子发生了什么。为什么融化过程中温度保持在 0 °C？
When ice is heated, the particles gain thermal energy and begin to vibrate more strongly.
当冰加热时，粒子获得热能并开始更剧烈地振动。
At 0 °C, the vibrations are strong enough to overcome the fixed lattice structure, and the solid turns into a liquid.
在 0 °C 时，振动足够强以克服固定的晶格结构，固体转变为液体。
During melting, the temperature remains constant because all the heat energy supplied is used to break the attractive forces between particles, not to raise the temperature.
在融化过程中，温度保持不变，因为所有提供的热能都用于打破粒子间的吸引力，而不是提高温度。
This energy is called the latent heat of fusion.
这种能量称为熔化潜热。
4. Atoms, Elements and the Periodic Table | 原子、元素与元素周期表
Question: What is an element? Give the chemical symbols for carbon, oxygen, sodium and iron.
问题：什么是元素？写出碳、氧、钠和铁的化学符号。
An element is a pure substance made up of only one type of atom. All atoms of an element have the same number of protons.
元素是由仅一种原子组成的纯净物。同一种元素的所有原子具有相同数量的质子。
Each element is represented by a unique chemical symbol, usually one or two letters. The first letter is always capitalised, and the second is lower case.
每种元素用一个独特的化学符号表示，通常是一或两个字母。第一个字母总是大写，第二个小写。
Carbon: C, Oxygen: O, Sodium: Na (from its Latin name ‘natrium’), Iron: Fe (from ‘ferrum’).
碳：C，氧：O，钠：Na（来自其拉丁名 ‘natrium’），铁：Fe（来自 ‘ferrum’）。
5. The Periodic Table Layout | 元素周期表排版
Question: Where are metals and non-metals found on the periodic table? Name one property of metals and one property of non-metals.
问题：元素周期表中金属和非金属分别位于何处？列出金属的一个性质和非金属的一个性质。
Metals are located on the left-hand side and in the centre of the periodic table, while non-metals are found on the right-hand side.
金属位于元素周期表的左侧和中间，而非金属位于右侧。
A typical property of metals is that they are good conductors of electricity and heat. For example, copper is used in electrical wires because it conducts electricity well.
金属的一个典型性质是它们是电和热的良导体。例如，铜用于电线是因为它导电性好。
A property of many non-metals is that they are poor conductors – they are often insulators. Sulphur, for instance, does not conduct electricity and is brittle.
许多非金属的一个性质是它们是差导体——通常是绝缘体。例如，硫不导电且易碎。
6. Compounds and Writing Chemical Formulas | 化合物与化学式的书写
Question: Explain the difference between a compound and a mixture. Write down the formula for carbon dioxide and state how many atoms of each element it contains.
问题：解释化合物和混合物的区别。写出二氧化碳的化学式，并说明它含有每种元素多少个原子。
A compound is a substance formed when two or more different elements are chemically bonded together. The elements are always present in fixed proportions.
化合物是两种或多种不同元素通过化学键结合形成的物质。这些元素总是以固定比例存在。
A mixture, on the other hand, contains two or more substances that are not chemically combined. The components can be separated by physical methods and their proportions can vary.
另一方面，混合物含有两种或多种没有通过化学键结合的物质。各组分可以通过物理方法分离，它们的比例可以变化。
Carbon dioxide has the formula CO₂. This shows it contains one carbon atom and two oxygen atoms bonded together.
二氧化碳的化学式为 CO₂。这表明它含有一个碳原子和两个键合在一起的氧原子。
7. Pure Substances and Melting Points | 纯净物与熔点
Question: A student measured the melting point of a white solid as 78–82 °C. Is the solid likely to be a pure compound? Justify your answer.
问题：一名学生测得一种白色固体的熔点为 78–82 °C。这种固体很可能是纯净化合物吗？说明理由。
A pure substance has a sharp, definite melting point. The narrow range of 78–82 °C suggests some impurities are present.
纯净物具有清晰、确定的熔点。78–82 °C 这个较窄的范围表明存在一些杂质。
Impurities broaden the melting range and often lower the melting point compared to the pure substance.
杂质会使熔点范围变宽，并且通常会降低熔点（与纯净物相比）。
Therefore, the solid is unlikely to be completely pure; it is probably a mixture or contains small amounts of another substance.
因此，这种固体不太可能是完全纯净的；它可能是混合物，或者含有少量其他物质。
8. Filtration: Separating an Insoluble Solid from a Liquid | 过滤：从液体中分离不溶性固体
Question: Describe how you would use filtration to separate sand from salty water. Which substance is collected as the residue?
问题：描述如何使用过滤从盐水中分离沙子。哪种物质作为残留物被收集？
Pour the mixture of sand and salty water through filter paper placed in a funnel. The filter paper has tiny pores that allow liquid to pass through but trap solid particles.
将沙子和盐水的混合物倒入放置在漏斗中的滤纸。滤纸具有微小的孔隙，允许液体通过但截留固体颗粒。
The sand is insoluble and too large to pass through the pores, so it stays on the filter paper as the residue.
沙子不溶且颗粒太大无法通过孔隙，因此它留在滤纸上作为残留物。
The salty water, called the filtrate, passes through and is collected in a beaker underneath. Filtration separates an insoluble solid from a liquid.
盐水，称为滤液，通过滤纸并收集在下方的烧杯中。过滤可将不溶性固体从液体中分离。
9. Evaporation and Crystallisation | 蒸发与结晶
Question: How can you obtain pure salt crystals from salty water? Explain why evaporation works.
问题：如何从盐水中获得纯净的盐晶体？解释蒸发为何有效。
Heat the salty water gently in an evaporating dish. As the water warms up, it gains energy and turns into water vapour, leaving the dissolved salt behind.
在蒸发皿中缓慢加热盐水。随着水温升高，水获得能量变成水蒸气，留下溶解的盐。
When enough water has evaporated, the solution becomes saturated and salt crystals begin to form. This process is called crystallisation.
当足够多的水蒸发后，溶液变得饱和，盐晶体开始形成。这个过程称为结晶。
Evaporation works because the salt does not evaporate – it has a much higher boiling point than water. Therefore, only the water is removed, leaving pure salt.
蒸发有效是因为盐不会蒸发——它的沸点比水高得多。因此，只有水被除去，留下纯净的盐。
10. Acids, Alkalis and Indicators | 酸、碱与指示剂
Question: What colour does litmus paper turn in an acidic solution and in an alkaline solution? Name one other indicator you could use.
问题：在酸性溶液和碱性溶液中石蕊试纸分别变成什么颜色？说出另一种你可以使用的指示剂。
Blue litmus paper turns red in an acidic solution, while red litmus paper turns blue in an alkaline solution.
蓝色石蕊试纸在酸性溶液中变红，而红色石蕊试纸在碱性溶液中变蓝。
A neutral solution leaves the litmus colour unchanged.
中性溶液不会改变石蕊的颜色。
Universal indicator is a mixture of several indicators and can show the full pH scale through a range of colours, from red for strong acids to purple for strong alkalis.
通用指示剂是几种指示剂的混合物，可以通过从强酸红色到强碱紫色的一系列颜色显示整个 pH 标度。
11. The pH Scale and Neutralisation | pH 标度与中和反应
Question: A solution has a pH of 3. Is it acidic, neutral or alkaline? What happens to the pH when a small amount of alkali is added? Write a word equation for the neutralisation reaction.
问题：一种溶液的 pH 为 3。它是酸性、中性还是碱性？加入少量碱后 pH 会怎样变化？写出中和反应的文字方程式。
A pH of 3 is acidic – the pH scale runs from 0 (very acidic) to 14 (very alkaline), with 7 being neutral.
pH 3 表示酸性——pH 标度从 0（强酸）到 14（强碱），7 为中性。
When an alkali is added, the acidic solution is partially neutralised, so the pH rises, moving closer to 7.
当加入碱时，酸性溶液被部分中和，因此 pH 升高，向 7 靠近。
The neutralisation reaction between an acid and an alkali produces a salt and water. For example:
酸和碱之间的中和反应生成盐和水。例如：
hydrochloric acid + sodium hydroxide → sodium chloride + water
盐酸 + 氢氧化钠 → 氯化钠 + 水
12. Evidence of a Chemical Reaction | 化学反应的证据
Question: List three observations that indicate a chemical reaction has taken place when magnesium ribbon is added to dilute hydrochloric acid.
问题：列出三条观察结果，表明将镁条加入稀盐酸中时发生了化学反应。
First, effervescence (fizzing) occurs, which shows that a gas is produced. The gas is hydrogen.
首先，出现冒泡现象（嘶嘶声），这表明有气体产生。该气体是氢气。
Second, the magnesium ribbon gradually disappears because it is being used up in the reaction.
其次，镁条逐渐消失，因为它在反应中被消耗掉了。
Third, the test tube feels warm – the reaction releases energy as heat, so it is an exothermic reaction.
第三，试管摸起来是热的——反应以热能的形式释放能量，因此是一个放热反应。
All these are clear signs that a new substance (magnesium chloride solution) is being formed.
所有这些都是新物质（氯化镁溶液）正在生成的明确迹象。
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