📚 763: States of Matter and the Particle Model for IGCSE Edexcel Science | 763：物质状态与粒子模型 – IGCSE爱德思科学
In IGCSE Edexcel Science, understanding the particle model of matter is the foundation for explaining everything from why solids keep their shape to how gases exert pressure. This article covers states of matter, changes of state, diffusion, gas pressure and the Kelvin temperature scale, all essential for your Double Award or Separate Science exams.
在IGCSE爱德思科学课程中，理解物质的粒子模型是解释从固体为何保持形状到气体如何产生压强等一切现象的基础。本文涵盖物质状态、状态变化、扩散、气体压强以及开尔文温标，这些内容对你的双奖或单科学考试都至关重要。
1. The Particle Model – Basic Ideas | 粒子模型的基本概念
All matter is made of tiny particles (atoms, molecules or ions) that are constantly moving. The key ideas of the particle model are: particles are in constant, random motion; there are forces of attraction between particles; and the amount of energy the particles have determines how they move and how far apart they are.
所有物质都是由不断运动的微小粒子（原子、分子或离子）组成的。粒子模型的核心思想是：粒子一直处于无规则运动状态；粒子之间存在吸引力；粒子所具有的能量大小决定了它们的运动方式和间距。
The model is a simplification – it treats particles as tiny spheres and ignores their internal structure. However, it successfully explains the properties of solids, liquids and gases.
这个模型是一种简化——它将粒子视为微小的球体，忽略了它们的内部结构。不过，它成功地解释了固体、液体和气体的性质。
2. Solids – Fixed Shape and Volume | 固体 – 固定的形状和体积
In a solid, the particles are packed closely together in a regular, repeating pattern. They vibrate about fixed positions but cannot move from place to place. This gives solids a definite shape and a definite volume; they cannot be compressed because there is very little space between particles.
固体中，粒子紧密地排列成规则的、重复的图案。粒子在固定位置附近振动，但不能自由移动。这使得固体具有确定的形状和确定的体积；它们不能被压缩，因为粒子间的空间极小。
When a solid is heated, the particles gain kinetic energy and vibrate more vigorously. This can eventually overcome the interparticle forces and cause melting.
固体受热时，粒子动能增加，振动更加剧烈。这最终可能克服粒子间的力，导致熔化。
3. Liquids – Fixed Volume but No Fixed Shape | 液体 – 体积固定但形状不固定
In a liquid, the particles are still close together but are arranged randomly rather than in a regular pattern. They have enough energy to slide past each other, so a liquid can flow and take the shape of its container. However, the volume remains constant because the particles remain in contact.
液体中，粒子仍然紧靠在一起，但排列是随机的，没有规则图案。它们有足够的能量相互滑动，因此液体可以流动并形成容器的形状。但体积保持不变，因为粒子仍保持接触。
Liquids are also very difficult to compress because there is little free space between the particles. Heating a liquid increases particle movement, and if enough energy is supplied, particles can break free to become a gas.
液体也很难被压缩，因为粒子之间几乎没有自由空间。加热液体会使粒子运动加剧，如果提供足够的能量，粒子可以挣脱束缚变成气体。
4. Gases – No Fixed Shape or Volume | 气体 – 无固定形状和体积
In a gas, the particles are widely spaced and move rapidly in all directions. They have negligible forces of attraction between them (except at the moment of collision). A gas fills its container completely, so it has no definite shape and no definite volume.
气体中，粒子间距很大，并朝各个方向快速运动。它们之间的吸引力几乎可以忽略不计（除非在碰撞瞬间）。气体会完全充满容器，因此没有固定的形状，也没有固定的体积。
Gases can be compressed easily because there is a great deal of empty space between particles. When you push the piston of a bicycle pump, you force the particles closer together.
气体很容易被压缩，因为粒子间存在大量空隙。当你推动自行车打气筒的活塞时，你在迫使粒子彼此靠近。
5. Changes of State and Energy | 状态变化与能量
When a substance changes state, energy is either absorbed or released, but the temperature remains constant during the change. For example, when ice melts to water at 0°C, the temperature stops rising even though you are still heating it. The energy goes into breaking the forces holding the particles in a rigid structure rather than raising their kinetic energy.
当物质发生状态变化时，能量会被吸收或释放，但在变化过程中温度保持不变。例如，冰在0°C熔化为水时，尽管继续加热，温度并不会上升。能量被用来破坏将粒子固定在刚性结构中的力，而不是增加它们的动能。
| Change of state | Direction | Energy change |
| Melting | Solid → Liquid | Energy absorbed |
| Boiling / Evaporating | Liquid → Gas | Energy absorbed |
| Freezing | Liquid → Solid | Energy released |
| Condensing | Gas → Liquid | Energy released |
| Sublimation | Solid → Gas | Energy absorbed |
状态变化方向与能量变化如上表。你必须能够解释为什么在熔点或沸点处加热曲线出现平台。
6. Melting and Boiling Points – Indicators of Purity | 熔点和沸点 – 纯度的指标
The melting point and boiling point of a substance are physical properties that can be used to identify it and check its purity. A pure substance melts and boils at sharp, specific temperatures. If impurities are present, the melting point usually falls and the boiling point rises; moreover, the substance will melt or boil over a range of temperatures rather than at a single point.
物质的熔点和沸点是物理性质，可用于鉴别物质并检查其纯度。纯物质在精确、特定的温度下熔化和沸腾。如果存在杂质，熔点通常会降低而沸点会升高；而且物质会在一个温度区间内熔化或沸腾，而不是在一个单点上。
For instance, pure water freezes at 0°C and boils at 100°C at standard pressure. Adding salt lowers the freezing point (useful for de-icing roads) and raises the boiling point slightly.
例如，纯水在标准压力下于0°C结冰，100°C沸腾。加入盐会降低凝固点（用于道路除冰），并轻微升高沸点。
7. Diffusion and the Particle Model | 扩散与粒子模型
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration, due to the random motion of particles. It occurs in gases and liquids but not in solids because the particles in solids are not free to move about.
扩散是粒子由于随机运动，从较高浓度区域向较低浓度区域净移动的过程。扩散发生在气体和液体中，但不会发生在固体中，因为固体中的粒子无法自由移动。
les have more kinetic energy and move faster. It also depends on the mass of the particles – r than hydrogen chloride (HCl, Mᵣ = 36.5) in the classic demonstration using a glass tube.
扩散速率随温度升高而加快，因为粒子动能更大、运动更快。扩散速率也取决于粒子质量——在相同温度下，较轻的粒子比较重的粒子扩散得更快。这就是在经典玻璃管实验中，氨气（NH₃，相对分子质量17）比氯化氢（HCl，相对分子质量36.5）扩散得快的原因。
8. Gas Pressure Explained by Particles | 用粒子解释气体压强
Gas pressure is caused by gas particles colliding with the walls of their container. Each collision exerts a tiny force; the total force over a given area is the pressure. If you increase the temperature of a gas (at constant volume), the particles move faster, collide more frequently and with greater force, so the pressure rises.
气体压强是由气体粒子撞击容器壁产生的。每次碰撞施加一个微小的力；分布在单位面积上的总力就是压强。如果在体积不变的情况下升高气体温度，粒子运动加快，碰撞更频繁且更有力，所以压强升高。
is described by the equation p₁V₁ = p₂V₂ for a fixed mass of gas at constant temperature.
如果在温度不变的情况下减小容器体积，粒子变得更拥挤，更频繁地撞击器壁，从而使压强增大。对于一定质量的气体在恒温条件下，这一关系用公式表示为：
p₁V₁ = p₂V₂
这个公式表明，压强与体积成反比。
9. Temperature, Kinetic Energy and Absolute Zero | 温度、动能与绝对零度
Temperature is a measure of the average kinetic energy of the particles in a substance. The Kelvin scale is the temperature scale used in gas law calculations because it starts at absolute zero (0 K). At absolute zero (−273°C), particles have the minimum possible energy and, theoretically, stop moving.
温度是物质中粒子平均动能的量度。开尔文温标是气体定律计算中使用的温标，因为它从绝对零度（0 K）开始。在绝对零度（−273°C）下，粒子具有理论上的最低能量，并且从理论上讲会停止运动。
θ(°C) + 273. Always use kelvins when working with pV = constant or similar relationships.
摄氏温标和开尔文温标之间的换算关系为：T(K) = θ(°C) + 273。在使用 pV = 常数或类似关系时，务必使用开尔文温度。
10. Explaining Everyday Phenomena with the Particle Model | 用粒子模型解释日常现象
The particle model helps explain many everyday observations: balloon inflation, the smell of perfume spreading, steam condensing on a bathroom mirror, and even why a can of fizzy drink sprays when opened. The can is under high pressure because CO₂ gas particles are dissolved and hitting the walls; opening the can reduces pressure, so the gas escapes rapidly, carrying liquid with it.
粒子模型有助于解释许多日常观察到的现象：气球膨胀、香水气味扩散、浴室镜子上水蒸气凝结，甚至为什么打开汽水罐时会喷溅。汽水罐内压强很高，因为溶解的CO₂气体粒子撞击罐壁；打开罐子会降低压强，气体迅速逸出，并带出液体。
Similarly, a sealed syringe half-filled with air can be compressed because the gas particles have large spaces between them. The same syringe filled with water cannot be compressed significantly because liquid particles are already close together.
同样，封口注射器若一半充满空气，可以被压缩，因为气体粒子之间有大量空间。而装满水的同一个注射器无法被显著压缩，因为液体粒子已经靠得很近。
11. Limitations of the Particle Model | 粒子模型的局限性
While the particle model is extremely useful, it has limitations. It does not account for the forces between particles in real substances in a quantitative way, nor does it explain why different solids have different structures (e.g. giant covalent vs molecular). It also treats particles as inelastic spheres, whereas real atoms and molecules can deform and interact in complex ways.
虽然粒子模型非常有用，但也有其局限性。它无法定量解释真实物质中粒子间的作用力，也不能解释为什么不同的固体具有不同的结构（例如巨型共价结构与分子结构）。此外，它把粒子视为没有弹性的球体，而真实的原子和分子可以变形并以复杂方式相互作用。
At IGCSE level, you are not expected to go beyond the simple model, but it is good to know that these simplifications exist.
在IGCSE阶段，你不需要超越简单模型，但了解这些简化之处是有好处的。
12. Exam Tips and Summary | 考试技巧与小结
When answering exam questions, always refer to the particle model for explanations of melting, boiling, diffusion and pressure. Use key terms like 'kinetic energy', 'intermolecular forces', 'random motion' and 'collisions with the walls'. For state change graphs, clearly identify the horizontal sections as the times when energy is used to overcome forces rather than to raise temperature.
在回答考试问题时，始终要引用粒子模型来解释熔化、沸腾、扩散和压强。使用诸如“动能”、“分子间力”、“随机运动”和“与器壁碰撞”等关键术语。对于状态变化图像，要明确指出水平段是能量被用来克服作用力而不是升高温度的阶段。
- Solid: particles close, regular pattern, vibrate in fixed positions – fixed shape and volume.
- Liquid: particles close, random arrangement, slide past each other – fixed volume, takes shape of container.
- Gas: particles far apart, move rapidly in all directions – no fixed shape or volume, easily compressed.
- Changes of state: occur at constant temperature; energy breaks or forms interparticle forces.
- Diffusion: faster at higher temperatures and for lighter particles.
- Gas pressure: caused by collisions; increases with temperature or decreasing volume.
- 固体：粒子紧密，规则排列，在固定位置振动——形状和体积固定。
- 液体：粒子紧密，随机排列，可相互滑动——体积固定，形状随容器而变。
- 气体：粒子间距很大，向各方向快速运动——无固定形状和体积，易压缩。
- 状态变化：发生在恒温条件下；能量破坏或形成粒子间作用力。
- 扩散：温度越高、粒子越轻，扩散越快。
- 气体压强：由碰撞引起；随温度升高或体积减小而增大。
Published by TutorHao | Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图