📚 The Particle Model of Matter | 物质的粒子模型
Understanding the particle model is essential for explaining the behaviour of solids, liquids and gases. This model helps scientists visualise how tiny particles — atoms, ions or molecules — are arranged and how they move.
理解粒子模型对于解释固体、液体和气体的行为至关重要。该模型帮助科学家形象化地理解微小粒子——原子、离子或分子——是如何排列和运动的。
1. What is the Particle Model? | 什么是粒子模型？
The particle model describes matter as being made up of very small particles that are constantly moving. The way these particles are arranged and move determines the state of the material.
粒子模型将物质描述为由非常微小的、不断运动的粒子构成。这些粒子的排列方式和运动状态决定了物质的形态。
In this model, particles are considered as solid spheres. However, in reality they are complex structures such as atoms and molecules.
在这个模型中，粒子被视为坚硬的球体。然而，实际上它们是原子和分子等复杂结构。
2. The Three States of Matter | 物质三态
There are three common states of matter: solid, liquid and gas. Each state has a distinct arrangement of particles.
物质有三种常见状态：固态、液态和气态。每种状态都有不同的粒子排列方式。
| State | Particle Arrangement | Particle Movement |
| Solid | Regular, closely packed | Vibrate about fixed positions |
| Liquid | Random, close together | Move around each other |
| Gas | Random, far apart | Move freely at high speed |
In a solid, particles are held in a fixed lattice and only vibrate. This gives solids a definite shape and volume.
在固体中，粒子被固定在晶格中，只能振动。这使得固体具有确定的形状和体积。
In a liquid, particles are still close together but can slide past one another. Therefore, liquids have a definite volume but take the shape of their container.
在液体中，粒子仍然紧密排列，但可以相互滑动。因此，液体具有确定的体积，但会随容器改变形状。
In a gas, particles are widely separated and move rapidly in all directions. Gases have neither a definite shape nor a definite volume.
在气体中，粒子相距很远，并朝各个方向快速运动。气体既没有确定的形状，也没有确定的体积。
3. Properties Explained by Particles | 用粒子解释物质性质
Solids are difficult to compress because their particles are already tightly packed. There is almost no empty space between them.
固体很难被压缩，因为其粒子已经紧密排列，粒子之间几乎没有空隙。
Liquids can flow because their particles can move past one another. The forces between particles are weaker than in solids.
液体能够流动是因为其粒子可以相互移动。粒子之间的作用力比固体弱。
Gases can be compressed easily because there is a lot of empty space between the particles. The particles are also very far apart, so the forces between them are negligible.
气体容易被压缩是因为粒子之间存在着大量空隙。粒子相距很远，因此它们之间的作用力可以忽略不计。
When a gas is compressed, the particles are forced closer together, reducing the empty space. The gas pressure increases.
当气体被压缩时，粒子被迫靠得更近，空隙变小，气体压力增大。
4. Changes of State | 状态变化
Matter can change from one state to another through heating or cooling. These changes are physical changes because no new substances are formed.
物质可以通过加热或冷却从一种状态变为另一种状态。这些变化是物理变化，因为没有新物质生成。
Melting is the change from solid to liquid. The temperature at which this happens is called the melting point.
熔化是固体变为液体的过程。该过程发生的温度称为熔点。
Boiling is the change from liquid to gas. It occurs throughout the liquid at a fixed temperature called the boiling point.
沸腾是液体变为气体的过程。它在液体内部整体进行，且发生在称为沸点的固定温度。
Evaporation is also a liquid-to-gas change, but it happens at the surface of the liquid and at any temperature below the boiling point.
蒸发也是液体变为气体的过程，但它发生在液体表面，并且可在低于沸点的任何温度下进行。
Condensation is the change from gas to liquid. Freezing is the change from liquid to solid.
冷凝是气体变为液体的过程。凝固是液体变为固体的过程。
Sublimation is the direct change from solid to gas, skipping the liquid state, such as solid carbon dioxide (dry ice).
升华是固体直接变为气体的过程，跳过液态，例如固态二氧化碳（干冰）。
5. Energy and Changes of State | 能量与状态变化
When a solid is heated, the particles absorb thermal energy and vibrate faster. At the melting point, the energy breaks the forces holding the particles in place.
当固体受热时，粒子吸收热能并加速振动。在熔点时，能量打破了使粒子保持固定的作用力。
During melting or boiling, the temperature does not rise even though heat is supplied. This energy is used to overcome the forces of attraction between particles, not to increase kinetic energy.
在熔化或沸腾过程中，尽管持续供热，温度并不会升高。这部分能量用于克服粒子之间的吸引力，而不是增加动能。
The energy needed to change a substance from solid to liquid at its melting point is called the latent heat of fusion.
在熔点处使物质从固态变为液态所需的能量称为熔化潜热。
The energy needed to change a liquid to a gas at its boiling point is called the latent heat of vaporisation.
在沸点处使液体变为气体所需的能量称为汽化潜热。
6. Diffusion | 扩散
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, due to their random motion.
扩散是粒子由于随机运动而从高浓度区域向低浓度区域的净移动。
Diffusion occurs in liquids and gases, but not in solids, because particles in solids cannot move freely.
扩散发生在液体和气体中，但不会发生在固体中，因为固体中的粒子不能自由移动。
For example, when a drop of ink is placed in water, the ink particles spread out until they are evenly distributed.
例如，将一滴墨水滴入水中，墨水粒子会扩散直到均匀分布。
Diffusion is faster in gases than in liquids because gas particles have more space and higher speeds.
气体中的扩散比液体中快，因为气体粒子有更多空间且运动速度更高。
Diffusion also depends on temperature. Higher temperature gives particles more kinetic energy, so they move faster and diffusion is quicker.
扩散还取决于温度。温度越高，粒子动能越大，运动越快，扩散也越快。
7. Brownian Motion | 布朗运动
Brownian motion is the irregular, random motion of tiny particles suspended in a fluid, caused by collisions with invisible molecules of the fluid.
布朗运动是悬浮在流体中的微小粒子的无规则运动，是由流体中不可见分子的碰撞引起的。
In 1827, Robert Brown observed that pollen grains in water moved continuously in a zigzag path. This provided evidence for the existence of molecules in motion.
1827年，罗伯特·布朗观察到水中的花粉颗粒沿着曲折路径持续运动。这为分子的存在和运动提供了证据。
Brownian motion can also be seen when smoke particles in air are viewed under a microscope. They jiggle because air molecules hit them from all sides.
在显微镜下观察空气中的烟粒也可以看到布朗运动。它们因为空气分子从各个方向碰撞而颤动。
This random motion supports the kinetic theory of matter, which states that particles are in constant motion.
这种无规则运动支持了物质的动力学理论，该理论认为粒子处于持续运动中。
8. Gas Pressure | 气体压力
Gas pressure is caused by gas particles hitting the walls of their container. Each collision exerts a small force, and many collisions create a steady pressure.
气体压力是由气体粒子撞击容器壁产生的。每次碰撞施加一个微小力，大量碰撞形成稳定的压力。
When the temperature of a gas increases, the particles move faster. They hit the walls more often and with greater force, so the pressure increases.
当气体温度升高时，粒子运动加快。它们更频繁、更有力地撞击容器壁，因此压力增大。
When the volume of a gas decreases at constant temperature, the particles are closer together and collide with the walls more often. Therefore, pressure increases.
在恒温下，当气体体积减小时，粒子靠得更近，与容器壁碰撞更频繁，因此压力增大。
This relationship is described by Boyle’s law for a fixed mass of gas at constant temperature:
这一关系由玻意耳定律描述，适用于恒温下固定质量的气体：
P₁V₁ = P₂V₂ 或 P ∝ 1 ÷ V
9. Density and the Particle Model | 密度与粒子模型
Density is defined as the mass per unit volume of a substance. The formula is:
密度定义为物质单位体积的质量。其公式为：
ρ = m ÷ V
where ρ (rho) is density in kg/m³, m is mass in kg, and V is volume in m³.
其中ρ（rho）是密度（单位kg/m³），m是质量（单位kg），V是体积（单位m³）。
In the particle model, density depends on the mass of the particles and how tightly they are packed.
在粒子模型中，密度取决于粒子的质量以及它们排列的紧密程度。
Solids generally have the highest density because their particles are tightly packed with little space between them. Gases have the lowest density because their particles are very far apart.
固体通常密度最大，因为其粒子紧密排列，之间空隙很小。气体密度最小，因为其粒子相距很远。
Water is an exception: ice is less dense than liquid water because the hydrogen bonds in ice force molecules into an open hexagonal structure, leaving more space.
水是一个例外：冰的密度小于液态水，因为冰中的氢键迫使分子形成开放的六边形结构，留下更多空间。
10. Applications of the Particle Model | 粒子模型的应用
The particle model helps explain everyday phenomena. For example, hot water dissolves sugar faster than cold water because the particles move more quickly and spread out faster.
粒子模型帮助解释日常现象。例如，热水比冷水溶解糖更快，因为粒子运动更快，扩散更快。
Perfume sprayed in one corner of a room can soon be smelt across the room due to diffusion of gas particles.
在房间一角喷洒香水，很快就能在房间另一侧闻到，这是因为气体粒子的扩散。
When a bicycle tyre is pumped, the pressure increases because more air particles are forced into the same volume, causing more frequent collisions with the tyre walls.
给自行车轮胎打气时，压力增大是因为更多空气粒子被压入相同体积中，导致与轮胎壁的碰撞更频繁。
In weather, evaporation of water from oceans and condensation into clouds can be explained using the particle model.
在天气现象中，海洋水的蒸发和云中的凝结也可以用粒子模型来解释。
11. Limitations of the Particle Model | 粒子模型的局限性
The simple particle model treats particles as solid spheres, but real particles are not spheres; atoms have complex internal structures.
简单的粒子模型将粒子视为实心球体，但实际粒子并不是球体；原子具有复杂的内部结构。
The model does not show the forces between particles accurately. In reality, these forces can be strong or weak depending on the substance and conditions.
该模型不能准确显示粒子之间的作用力。实际上，这些作用力根据物质和条件的不同而有强有弱。
Also, the model does not describe the behaviour of electrons or nuclear reactions. It is only useful for explaining physical changes of matter.
此外，该模型不能描述电子或核反应的行为。它仅用于解释物质的物理变化。
Despite these limitations, the particle model remains a powerful tool for understanding the physical world at a simple level.
尽管存在这些局限性，粒子模型仍然是理解物理世界基础层面的有力工具。
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