IB & AQA Science: States of Matter – Key Revision Notes | IB AQA 科学：物质状态

📚 IB & AQA Science: States of Matter – Key Revision Notes | IB AQA 科学：物质状态 – 考点精讲

Understanding states of matter is essential for both IB and AQA science courses. This revision guide covers the particle model, changes of state, gas laws, diffusion, and key exam tips to help you master the topic with confidence.

理解物质的状态是 IB 与 AQA 科学课程的基础。本复习指南涵盖粒子模型、状态变化、气体定律、扩散以及关键考试技巧，帮助你扎实掌握这一主题。

1. The Three States of Matter and Particle Theory | 物质的三态与粒子理论

All matter is made of tiny particles that are constantly moving. The arrangement and motion of these particles determine whether a substance is a solid, liquid, or gas.

所有物质都由不断运动的微小粒子构成。粒子的排列方式和运动情况决定了一种物质是固体、液体还是气体。

In solids, particles are tightly packed in a fixed, regular pattern. They vibrate around fixed positions but cannot move past one another, giving solids a definite shape and volume.

在固体中，粒子紧密排列成固定的规则结构。它们在固定位置振动，但无法自由移动，因此固体有固定的形状和体积。

In liquids, particles are still close together but arranged randomly. They can slide past each other, allowing liquids to flow and take the shape of their container while maintaining a fixed volume.

在液体中，粒子仍然紧密聚集但排列随机。它们可以相互滑动，使得液体能够流动并呈现容器的形状，同时保持固定的体积。

In gases, particles are far apart with no regular arrangement. They move rapidly in all directions, filling any container entirely. Gases have no fixed shape or volume.

在气体中，粒子相距很远，无规则排列。它们向各个方向快速运动，能够完全充满任意容器。气体没有固定的形状和体积。

2. Properties of Solids, Liquids and Gases | 固体、液体和气体的性质

The differences in particle behaviour lead to distinct macroscopic properties. A comparison table helps summarise these properties clearly.

粒子行为的不同导致了宏观性质的差异。下表清晰地总结了这些性质对比。

Property	Solid	Liquid	Gas
Shape	Fixed	Takes shape of container	Fills container completely
Volume	Fixed	Fixed	Not fixed
Compressibility	Very low	Very low	High
Density	High	Usually slightly lower than solid	Very low
Particle motion	Vibrate only	Slide past each other	Fast, random, straight-line motion

In exams, you may need to explain these differences using the particle model. Always link the observed property to the arrangement and energy of the particles.

考试中你可能需要用粒子模型解释这些差异。始终将观察到的性质与粒子的排列和能量联系起来。

3. Changes of State and Energy Transfer | 状态变化与能量转移

When a substance changes state, energy is transferred to or from the particles. This breaks or forms inter-particle bonds rather than raising the temperature.

当物质改变状态时，能量会向粒子传递或从粒子释放。这些能量用于打破或形成粒子间的键合，而不是改变温度。

Melting and boiling require energy input (endothermic). During these changes, the temperature remains constant despite continuous heating.

熔化和沸腾需要吸热（吸热过程）。在这些变化过程中，即使持续加热，温度也保持恒定。

Freezing and condensation release energy (exothermic). The particles lose kinetic energy and move closer together, forming stronger bonds.

凝固和凝结释放能量（放热过程）。粒子失去动能，彼此靠近，形成更牢固的键合。

The energy needed to melt 1 kg of a solid at its melting point is the specific latent heat of fusion. The energy needed to boil 1 kg of a liquid is the specific latent heat of vaporisation.

使1千克固体在其熔点完全熔化所需的能量称为熔化比潜热。使1千克液体完全沸腾所需的能量叫作汽化比潜热。

Equation: E = m L, where E is energy transferred (J), m is mass (kg), and L is the specific latent heat (J/kg).

公式：E = m L，其中E为传递的能量（焦耳），m为质量（千克），L为比潜热（焦耳/千克）。

4. Diffusion and Brownian Motion | 扩散与布朗运动

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration. It occurs because particles are in constant random motion.

扩散是粒子从高浓度区域向低浓度区域的净运动。它之所以发生是因为粒子不断做无规则运动。

Diffusion is fastest in gases, slower in liquids, and extremely slow in solids. Higher temperatures increase the kinetic energy of particles, making diffusion faster.

扩散在气体中最快，液体中较慢，固体中极其缓慢。温度升高会增加粒子的动能，从而加速扩散。

Brownian motion provides evidence for the particle model. When large, visible particles (e.g. smoke or pollen) are suspended in a fluid, they jiggle randomly due to collisions with much smaller, invisible particles.

布朗运动为粒子模型提供了证据。将较大的可见颗粒（如烟雾或花粉）悬浮在流体中时，它们会发生随机抖动，这是因为它们与更小、看不见的粒子发生了碰撞。

This random motion cannot be explained unless the fluid consists of tiny, fast-moving particles. Remember that Brownian motion refers to the movement of the large particles, not the fluid particles themselves.

这种随机运动只有用流体由微小、快速运动的粒子组成才能解释。请注意，布朗运动指的是大颗粒的运动，而不是流体粒子本身的运动。

5. Gas Pressure and the Particle Model | 气体压强与粒子模型

Gas pressure is caused by the force exerted by gas particles when they collide with the walls of their container. Each collision produces a tiny outward push.

气体压强是由气体粒子碰撞容器壁时施加的力引起的。每一次碰撞都会产生一个微小的向外推力。

The total pressure depends on how often the collisions occur and the force of each collision. The particle model explains this beautifully: if particles hit the walls more frequently or with greater force, the pressure rises.

总压强取决于碰撞发生的频率和每次碰撞的力度。粒子模型能很好地解释这一点：如果粒子更频繁地碰撞壁面，或者每次碰撞的力度更大，压强就会升高。

In a sealed container, the gas particles are in constant, rapid motion. When you increase the temperature, the particles gain kinetic energy and hit the walls harder and more often, increasing the pressure (if volume is fixed).

在密封容器中，气体粒子持续快速运动。升高温度时，粒子获得动能，更猛烈、更频繁地撞击壁面，从而使压强增大（若体积固定）。

6. Factors Affecting Gas Pressure | 影响气体压强的因素

For a fixed mass of gas at constant volume, pressure is directly proportional to the absolute temperature (in Kelvin). If temperature doubles, the average kinetic energy doubles, and so does the pressure.

对于质量固定、体积不变的气体，压强与绝对温度（开尔文）成正比。若温度变为两倍，平均动能也变为两倍，压强同样变为两倍。

If temperature is kept constant, increasing the volume of the container gives particles more space. They hit the walls less frequently, so pressure decreases.

如果温度保持不变，增大容器体积会让粒子有更多空间。它们撞击壁面的频率降低，因此压强减小。

Decreasing the volume forces particles closer together, leading to more frequent collisions and thus higher pressure. These relationships are the basis of the gas laws.

减小体积会迫使粒子更加靠近，导致碰撞更频繁，因此压强升高。这些关系是气体定律的基础。

7. Boyle’s Law (Pressure-Volume Relationship) | 波义耳定律（压强-体积关系）

Boyle’s Law states that for a fixed mass of gas at constant temperature, pressure is inversely proportional to volume. This can be written as:

波义耳定律指出，对于质量固定、温度不变的气体，压强与体积成反比。可表示为：

P₁ V₁ = P₂ V₂

where P is pressure and V is volume. If you halve the volume, the pressure doubles, provided the temperature does not change.

其中 P 表示压强，V 表示体积。如果体积减半，压强就会加倍，前提是温度不变。

Use this equation in calculations. Make sure units for pressure and volume are consistent on both sides of the equation. For example, if P₁ is in kPa and V₁ in cm³, then P₂ will be in kPa and V₂ in cm³.

在计算中使用该等式。确保等式两边压强和体积的单位一致。例如，如果 P₁ 的单位是千帕，V₁ 是立方厘米，那么 P₂ 就应该是千帕，V₂ 是立方厘米。

Remember that Boyle’s Law only applies when the temperature remains constant. If temperature changes, you must consider the combined gas law or the ideal gas equation.

记住波义耳定律只在温度保持不变时适用。如果温度发生变化，就需要考虑组合气体定律或理想气体方程。

8. Charles’ Law (Volume-Temperature Relationship) | 查理定律（体积-温度关系）

Charles’ Law describes how the volume of a gas changes with temperature when pressure is constant. It states that volume is directly proportional to absolute temperature (in Kelvin).

查理定律描述了压强恒定时气体体积随温度变化的规律。它指出体积与绝对温度（开尔文）成正比。

V₁ / T₁ = V₂ / T₂

If the temperature of a gas is increased from 300 K to 600 K at constant pressure, its volume doubles. Always convert Celsius temperatures to Kelvin by adding 273 before using this law.

若恒定压强下气体温度从300 K升至600 K，其体积加倍。使用此定律前务必将摄氏温度换算为开尔文，即加273。

Both Boyle’s and Charles’ laws can be explained by the particle model. Higher temperature means faster particles that push outward more, requiring a larger volume to keep pressure constant.

波义耳定律和查理定律都可以用粒子模型解释。更高的温度意味着粒子运动更快，向外推力更大，需要更大的体积来维持压强恒定。

9. Evaporation vs. Boiling | 蒸发与沸腾的区别

Evaporation occurs at the surface of a liquid at any temperature. Higher energy particles near the surface escape into the air, lowering the average kinetic energy of the remaining liquid, which cools it down.

蒸发可以在任意温度下于液体表面发生。液面附近高能量的粒子逃逸到空气中，降低剩余液体的平均动能，从而使液体冷却。

Boiling occurs throughout the liquid at a specific temperature called the boiling point. At this temperature, bubbles of vapour form within the liquid and rise to the surface.

沸腾发生在整个液体当中，需达到特定的温度，即沸点。在此温度下，液体内部形成蒸汽泡并上升到液面。

Both processes involve a change from liquid to gas, but boiling requires an external energy source to maintain the temperature, whereas evaporation can happen spontaneously using internal energy.

这两个过程都涉及从液体到气体的变化，但沸腾需要外部热源维持温度，而蒸发可以利用内能自发发生。

Factors that speed up evaporation include higher temperature, larger surface area, and airflow that removes vapour from the surface.

加速蒸发的因素包括温度升高、表面积增大以及将液面蒸汽带走的空气流动。

10. Heating and Cooling Curves | 加热与冷却曲线

A heating curve shows how the temperature of a substance changes over time as heat is added. Plateaus appear at the melting and boiling points where energy is used to change state rather than increase temperature.

加热曲线显示随着热量加入，物质温度如何随时间变化。在熔点和沸点处会出现平台，此时能量用于改变状态而不是提高温度。

On a cooling curve, temperature drops until it reaches the melting or boiling point. The temperature then stays constant while the substance freezes or condenses, releasing latent heat.

在冷却曲线上，温度下降直到达到熔点或沸点。然后温度保持不变，物质凝固或凝结，同时释放潜热。

These curves are powerful tools for identifying physical properties. The length of the plateau relates to the amount of latent heat and the mass of the substance. Be prepared to interpret such graphs in exams.

这些曲线是确定物理性质的有力工具。平台的长度与潜热量和物质质量有关。准备好考试中解读这些图表。

11. Advanced Concepts: Sublimation and Deposition | 进阶概念：升华与凝华

Some substances can change directly from solid to gas, skipping the liquid phase. This is called sublimation. Solid carbon dioxide (dry ice) and iodine are classic examples.

有些物质可以直接从固态变为气态，跳过液态阶段。这称为升华。固体二氧化碳（干冰）和碘是典型例子。

The reverse process, where a gas changes directly into a solid, is known as deposition. Frost forming on a cold surface is a common example of deposition from water vapour.

相反的过程，气体直接变为固体，叫作凝华。在冷表面上形成的霜就是水蒸气凝华的常见例子。

In the particle model, sublimation occurs when particles at the solid surface gain enough energy to overcome attractive forces and escape directly into the gas phase. This is an endothermic process.

在粒子模型中，当固体表面的粒子获得足够能量克服吸引力并直接逃逸到气相时，就会发生升华。这是一个吸热过程。

Deposition releases energy (exothermic) as gas particles lose kinetic energy and settle into an ordered solid structure.

凝华释放能量（放热），因为气体粒子失去动能并沉降为有序的固体结构。

12. Summary and Exam Tips | 总结与考试技巧

Always use the particle model to explain macroscopic observations. Link properties like shape, volume, and compressibility to particle arrangement and motion.

始终用粒子模型解释宏观观察。将形状、体积和可压缩性等性质与粒子排列和运动联系起来。

Remember key formulas: E = m L for latent heat, P₁V₁ = P₂V₂ for constant temperature, and V₁/T₁ = V₂/T₂ for constant pressure. Use Kelvin for temperature.

记住关键公式：潜热 E = m L，恒温下 P₁V₁ = P₂V₂，恒压下 V₁/T₁ = V₂/T₂。温度使用开尔文。

When drawing heating or cooling curves, label the axes correctly and indicate the state at each segment. The flat lines correspond to changes of state.

绘制加热或冷却曲线时，正确标记坐标轴并标明每一段对应的状态。水平线对应状态变化。

Be precise with scientific language. Instead of saying ‘particles move faster’, say ‘the average kinetic energy of the particles increases’. This will earn you higher marks.

科学语言要精确。不要只说“粒子运动更快”，而要说“粒子的平均动能增加”。这会让你获得更高分数。

Finally, practice applying gas laws to everyday situations, such as syringes, balloons, and pressure cookers. This helps you answer application questions confidently.

最后，多练习将气体定律应用到注射器、气球和高压锅等日常情景。这有助于你自信地回答应用题。

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IB & AQA Science: States of Matter – Key Revision Notes | IB AQA 科学：物质状态 – 考点精讲