KS3 Chemistry Unit 5 Review | KS3 化学第五单元复习

📚 KS3 Chemistry Unit 5 Review | KS3 化学第五单元复习

This review brings together the main ideas met in KS3 chemistry, from the particle model and changes of state to elements, compounds, reactions, acids and everyday processes. It is written to help you check understanding, recall key definitions and practise using word equations and models accurately.

本复习将 KS3 化学的主要概念汇集在一起，从粒子模型和状态变化，到元素、化合物、化学反应、酸以及日常过程。它旨在帮助你检查理解、回忆关键定义，并准确练习使用文字方程式和模型。

1. States of Matter and the Particle Model | 物质状态与粒子模型

All matter is made of tiny particles. In a solid, the particles are packed tightly in a regular arrangement, vibrate about fixed positions and cannot change places; in a liquid, the particles are close together but can move past one another; in a gas, the particles are far apart, move quickly and randomly, and fill their container.

所有物质都由微小的粒子组成。在固体中，粒子紧密地以规则排列堆积，在固定位置振动，不能互换位置；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，快速且无规则地运动，并充满容器。

Solid: fixed shape and fixed volume | 固体：形状和体积固定
Liquid: fixed volume but takes the shape of the container | 液体：体积固定但取容器形状
Gas: no fixed shape or volume | 气体：没有固定形状或体积

The particle model explains why solids cannot flow, why liquids can be poured and why gases spread out. It also helps us predict how a substance will behave when it is heated or cooled.

粒子模型解释了为什么固体不能流动、液体可以倾倒、气体会扩散。它还帮助我们预测物质在加热或冷却时的行为。

2. Changes of State and Energy | 状态变化与能量

Changing state is a physical change because no new substance is made. The main changes are melting, freezing, boiling, condensing, sublimation and deposition. During melting and boiling, energy is taken in by the particles; during freezing and condensing, energy is released.

状态变化是物理变化，因为没有生成新物质。主要变化包括熔化、凝固、沸腾、冷凝、升华和凝华。在熔化和沸腾过程中，粒子吸收能量；在凝固和冷凝过程中，粒子释放能量。

The temperature of a pure substance stays constant while it changes state. For water, melting occurs at 0 °C and boiling occurs at 100 °C at normal pressure.

纯物质在状态变化期间温度保持不变。水在常压下熔点为 0 °C，沸点为 100 °C。

solid ⇌ liquid ⇌ gas

You should be able to sketch a heating curve and label the flat sections where melting and boiling happen. These flat parts show that energy is being used to break forces between particles, not to raise temperature.

你应该能够画出加热曲线，并标出发生熔化和沸腾的平坦部分。这些平坦部分表明能量被用于破坏粒子间的作用力，而不是用于升高温度。

3. Elements, Compounds and Mixtures | 元素、化合物和混合物

An element is made of only one type of atom and cannot be broken down into simpler substances by chemical means. A compound contains two or more different elements chemically joined together in a fixed ratio. A mixture contains different substances that are not chemically bonded and can be separated by physical methods.

元素只由一种原子组成，不能通过化学方法分解为更简单的物质。化合物含有两种或更多种不同元素，以固定比例通过化学键结合。混合物含有不同物质，它们没有通过化学键结合，可以通过物理方法分离。

Element example: oxygen, iron, sulfur | 元素例子：氧、铁、硫
Compound example: water, carbon dioxide, sodium chloride | 化合物例子：水、二氧化碳、氯化钠
Mixture example: air, seawater, salt and sand | 混合物例子：空气、海水、盐和沙

Mixtures can be separated using filtration, evaporation, distillation or chromatography. These methods depend on physical properties such as particle size, boiling point or solubility.

混合物可以通过过滤、蒸发、蒸馏或色谱法分离。这些方法取决于物理性质，如粒子大小、沸点或溶解度。

4. Atomic Structure and the Periodic Table | 原子结构与元素周期表

Atoms contain protons, neutrons and electrons. Protons have a positive charge, neutrons have no charge, and electrons have a negative charge. The protons and neutrons are found in the nucleus, while electrons move around the outside in shells.

原子包含质子、中子和电子。质子带正电荷，中子不带电荷，电子带负电荷。质子和中子位于原子核内，而电子在核外的电子层中运动。

The atomic number is the number of protons in an atom. In a neutral atom, the number of protons equals the number of electrons. The mass number is the total number of protons plus neutrons.

原子序数是原子中质子的数量。在中性原子中，质子数等于电子数。质量数是质子数与中子数之和。

The periodic table arranges elements in order of atomic number. Elements in the same group have similar chemical properties because they have the same number of outer-shell electrons. Metals are found on the left and centre, non-metals on the right.

元素周期表按原子序数排列元素。同一主族元素具有相似的化学性质，因为它们具有相同数量的最外层电子。金属位于左侧和中部，非金属位于右侧。

5. Chemical Reactions and Word Equations | 化学反应与文字方程式

A chemical change makes new substances. Signs of a chemical reaction include a colour change, a gas being given off, a precipitate forming, a temperature change or light being produced.

化学变化会产生新物质。化学反应的迹象包括颜色变化、放出气体、形成沉淀、温度变化或产生光。

A word equation shows the reactants on the left and the products on the right, with an arrow meaning ‘turns into’. For example:

文字方程式将反应物写在左侧，生成物写在右侧，箭头表示“转变成”。例如：

magnesium + oxygen → magnesium oxide

Mass is conserved in chemical reactions. The total mass of the reactants equals the total mass of the products because atoms are only rearranged, not created or destroyed.

化学反应中质量守恒。反应物的总质量等于生成物的总质量，因为原子只是重新排列，没有被创造或消灭。

6. Acids and Alkalis | 酸与碱

Acids have a pH less than 7, neutral solutions have a pH of 7, and alkalis have a pH greater than 7. The pH scale usually runs from 0 to 14. Indicators such as litmus and universal indicator are used to test pH.

酸的 pH 小于 7，中性溶液的 pH 等于 7，碱的 pH 大于 7。pH 标度通常从 0 到 14。石蕊和通用指示剂等指示剂用于测试 pH。

Acid: pH 0-6, litmus red | 酸：pH 0-6，石蕊变红
Neutral: pH 7, litmus purple | 中性：pH 7，石蕊呈紫色
Alkali: pH 8-14, litmus blue | 碱：pH 8-14，石蕊变蓝

Neutralisation occurs when an acid and an alkali react together. The general word equation is:

酸和碱反应时发生中和反应。一般的文字方程式为：

acid + alkali → salt + water

Common examples include hydrochloric acid with sodium hydroxide, producing sodium chloride and water. You should be able to name the salt formed from a given acid and alkali.

常见例子包括盐酸与氢氧化钠反应，生成氯化钠和水。你应该能够根据给定的酸和碱命名生成的盐。

7. Metals, Non-metals and Reactivity | 金属、非金属与反应性

Metals are usually shiny, good conductors of heat and electricity, malleable and ductile. Non-metals are often dull, poor conductors, and brittle when solid. Most elements are metals.

金属通常有光泽，是良好的热和电导体，具有延展性和韧性。非金属通常暗淡无光，是较差的导体，固态时易碎。大多数元素是金属。

The reactivity series lists metals in order of how strongly they react. A common KS3 order is:

金属活动性顺序列出金属反应的强弱。KS3 常用的顺序为：

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

More reactive metals react more quickly with acid and oxygen. For example, magnesium burns with a bright white flame, while copper does not react quickly with dilute acid at room temperature.

活泼金属与酸和氧反应更快。例如，镁燃烧产生明亮的白色火焰，而铜在室温下与稀酸反应不迅速。

metal + acid → salt + hydrogen

Hydrogen can be tested with a burning splint, which gives a squeaky pop. This is a key test for the gas produced when a metal reacts with an acid.

氢气可用燃烧的 splint 检验，会发出爆鸣声。这是金属与酸反应生成气体的重要检验方法。

8. Environmental Chemistry and Everyday Reactions | 环境化学与日常反应

Burning fuels releases carbon dioxide and water when the fuel burns completely. Incomplete combustion can produce carbon monoxide and carbon particles. These emissions affect air quality and contribute to climate change.

燃料完全燃烧时释放二氧化碳和水。不完全燃烧会产生一氧化碳和碳颗粒。这些排放物会影响空气质量，并导致气候变化。

Acid rain forms when sulfur dioxide and nitrogen oxides dissolve in rainwater. These gases come from burning fossil fuels. Acid rain damages buildings, soils and aquatic life.

酸雨是二氧化硫和氮氧化物溶解在雨水中形成的。这些气体来自化石燃料的燃烧。酸雨会损害建筑物、土壤和水生生物。

Carbonates react with acids to produce salt, water and carbon dioxide. This can be shown as:

碳酸盐与酸反应生成盐、水和二氧化碳。可表示为：

carbonate + acid → salt + water + carbon dioxide

Carbon dioxide can be tested with limewater. If the gas is present, limewater turns cloudy or milky.

二氧化碳可用石灰水检验。如果存在该气体，石灰水会变浑浊或呈乳白色。

Recycling metals and glass reduces the use of raw materials and energy. Everyday reactions such as rusting involve iron, oxygen and water; rusting can be prevented by painting, oiling or galvanising.

回收金属和玻璃可减少原材料和能源的使用。日常反应如生锈涉及铁、氧气和水；可通过涂漆、涂油或镀锌来防止生锈。

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KS3 Chemistry Unit 5 Review | KS3 化学第五单元复习