📚 KS3 Activate Chemistry: Particles and Their Behaviour | KS3 Activate 化学：粒子及其行为
Everything you see, smell, touch and taste is made from matter. Matter is built from tiny particles that are much too small to see with the naked eye. In this Oxford KS3 Activate Chemistry topic, we explore the particle model, the three states of matter, changes of state, diffusion, gas pressure, density, mixtures and the key exam descriptions you need to master.
你看到、闻到、摸到和尝到的一切都是由物质组成的。物质由微小的粒子构成，这些粒子小到用肉眼无法看见。在这篇牛津 KS3 Activate 化学主题文章中，我们将学习粒子模型、物质的三态、物态变化、扩散、气体压强、密度、混合物，以及你必须掌握的关键考试描述。
1. The Particle Model | 粒子模型
The particle model is a simple scientific way to explain how matter behaves. It states that all substances are made from tiny, moving particles. The particles themselves are the same in solids, liquids and gases; what changes is their arrangement, their movement and the spaces between them.
粒子模型是解释物质行为的一种简单科学方法。它指出所有物质都由微小的、不断运动的粒子组成。固体、液体和气体中的粒子本身是相同的，变化的是它们的排列方式、运动状态以及它们之间的间隔。
The particle model helps us explain familiar observations such as why solids keep their shape, why liquids flow, and why gases spread out. It is not a perfect picture of real atoms and molecules, but it is extremely useful at KS3 level.
粒子模型帮助我们解释一些常见的现象，例如为什么固体能保持形状、为什么液体会流动、为什么气体会扩散。它并不是真实原子和分子的完美图像，但在 KS3 阶段非常有用。
2. States of Matter | 物质的三态
Matter usually exists in one of three states: solid, liquid or gas. These are called the three states of matter. The state of a substance depends on how much energy its particles have and how strongly they are attracted to one another.
物质通常以三种状态之一存在：固态、液态或气态。它们被称为物质的三态。物质处于哪种状态取决于其粒子具有多少能量，以及粒子之间的相互吸引力有多强。
The table below summarises the particle arrangement and movement in each state.
下表总结了每种状态下粒子的排列方式和运动情况。
| State | Arrangement of particles | Movement of particles |
|---|---|---|
| Solid | Very close, regular pattern | Vibrate in fixed positions |
| Liquid | Close, random arrangement | Move around each other |
| Gas | Far apart, random arrangement | Move quickly in all directions |
When a substance changes state, its particles do not change into new particles. Only their arrangement and movement change.
当物质改变状态时，其粒子并没有变成新的粒子，改变的只是它们的排列方式和运动方式。
3. Properties of Solids, Liquids and Gases | 固体、液体和气体的性质
Solids have a fixed shape and a fixed volume because their particles are strongly held in place. They cannot be compressed easily because the particles are already very close together.
固体有固定的形状和固定的体积，因为它们的粒子被牢固地固定在原处。固体不容易被压缩，因为粒子已经非常紧密地排列在一起。
Liquids have a fixed volume but no fixed shape. They take the shape of the bottom of a container and can flow because their particles can slide over one another. Liquids are also very difficult to compress.
液体有固定的体积，但没有固定的形状。它们会呈现容器底部的形状，并且可以流动，因为其粒子可以相互滑动。液体也很难被压缩。
Gases have no fixed shape and no fixed volume. They spread out to fill the whole container. Gases can be compressed easily because their particles are far apart, with large spaces between them.
气体没有固定的形状，也没有固定的体积。它们会扩散并充满整个容器。气体很容易被压缩，因为它们的粒子相距很远，粒子之间有较大的空间。
4. Changes of State | 物态变化
When a solid is heated, its particles gain energy and vibrate more strongly. At the melting point, the particles have enough energy to break free from their fixed positions, and the solid changes into a liquid. This process is called melting.
当固体受热时，其粒子获得能量并振动得更剧烈。在熔点时，粒子获得足够的能量脱离固定的位置，固体就变成了液体。这个过程叫做熔化。
Further heating causes the liquid particles to gain more energy. At the boiling point, bubbles of gas form throughout the liquid and the liquid changes into a gas. If the change happens only at the surface, it is called evaporation.
继续加热会使液体粒子获得更多能量。在沸点时，整个液体中会形成气泡，液体变成气体。如果这种变化只发生在液体表面，就叫做蒸发。
Cooling a gas causes its particles to lose energy and move closer together. When a gas becomes a liquid, it is called condensing. When a liquid becomes a solid, it is called freezing.
冷却气体会使粒子失去能量并彼此靠近。气体变成液体的过程叫做凝结。液体变成固体的过程叫做凝固。
The main changes of state are shown below.
主要的物态变化如下图所示。
solid ⇌ liquid ⇌ gas
The forward arrows require heating; the reverse arrows require cooling.
向前的箭头表示需要加热，向后的箭头表示需要冷却。
5. Melting and Boiling Points | 熔点与沸点
A pure substance has a sharp melting point and a sharp boiling point. This means it melts or boils at one particular temperature, not over a wide range. Water melts at 0 °C and boils at 100 °C at normal atmospheric pressure.
纯净物有固定的熔点和固定的沸点。这意味着它会在一个特定的温度下熔化或沸腾，而不是在一个很宽的温度范围内。在标准大气压下，水在 0 °C 熔化，在 100 °C 沸腾。
Melting and boiling points can be used to identify an unknown substance. If a sample melts over a range of temperatures, it is probably a mixture rather than a pure substance.
熔点和沸点可以用来鉴别未知物质。如果某样品在一个温度范围内熔化，它很可能是一种混合物，而不是纯净物。
At the melting point, heating energy is used to overcome the forces between particles, not to raise the temperature. This is why the temperature stays constant while a pure solid melts.
在熔点时，加热能量用于克服粒子之间的作用力，而不是用于升高温度。这就是为什么纯净固体在熔化时温度保持不变。
6. Diffusion in Liquids and Gases | 液体和气体中的扩散
Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. It happens because particles move randomly in all directions and spread out into any available space.
扩散是粒子从浓度较高的区域向浓度较低的区域移动的过程。它会发生是因为粒子朝各个方向无规则运动，并扩散到任何可利用的空间中。
Diffusion is fastest in gases, slower in liquids, and extremely slow in solids. This is because gas particles move quickly and have large spaces between them, while solid particles can only vibrate in fixed positions.
扩散在气体中最快，在液体中较慢，在固体中极慢。这是因为气体粒子运动速度快，粒子之间的间隔大，而固体粒子只能在固定位置上振动。
A common example is perfume spreading across a room. The perfume particles collide with air particles and gradually move from where they are concentrated near the bottle to the rest of the room.
一个常见的例子是香水在房间中扩散。香水粒子与空气粒子碰撞，逐渐从瓶子附近浓度较高的区域移动到房间的其他地方。
7. Gas Pressure | 气体压强
Gas particles move rapidly in all directions and collide with the walls of their container. Each collision exerts a small force on the wall. The total force acting per unit area of the wall is called gas pressure.
气体粒子快速地向各个方向运动，并与容器壁发生碰撞。每次碰撞都会对容器壁施加一个很小的力。作用在容器壁单位面积上的总力叫做气体压强。
pressure = force ÷ area
If the volume of a gas is kept the same, heating the gas increases its pressure. The particles gain kinetic energy, move faster, and collide with the walls more often and with greater force.
如果气体的体积保持不变，加热气体会使其压强增大。粒子获得动能，运动加快，并且更频繁、更有力地撞击容器壁。
If the container can expand, heating a gas may increase its volume instead of its pressure. Understanding this helps explain how balloons expand in warm air and how bicycle tyres become harder when pumped up.
如果容器可以膨胀，加热气体可能会使其体积增大，而不是压强增大。理解这一点有助于解释气球在暖空气中为什么会膨胀，以及自行车轮胎打气后为什么会变硬。
8. Density and the Particle Model | 密度与粒子模型
Density is the mass of a substance per unit volume. It is a measure of how tightly packed the particles are. In general, solids are denser than liquids, and liquids are denser than gases.
密度是物质单位体积的质量。它是粒子排列紧密程度的一种量度。一般来说，固体的密度大于液体，液体的密度大于气体。
density = mass ÷ volume
There are important exceptions. Ice floats on water because ice is less dense than liquid water. This happens because water particles arrange themselves in an open structure when they freeze, leaving more space between them.
但也有重要的例外。冰能浮在水面上，是因为冰的密度小于液态水。这是因为水在结冰时粒子排列成开放的结构，粒子之间的间隔变大。
Using the particle model, you can explain floating and sinking. If an object is less dense than water, the upward force from the water is greater than the object’s weight, so the object floats.
利用粒子模型，你可以解释浮沉现象。如果物体的密度小于水，水对物体的向上作用力大于物体的重力，所以物体就会漂浮。
9. Pure Substances and Mixtures | 纯净物与混合物
A pure substance contains only one type of particle or one type of compound. Water, salt and oxygen are examples of pure substances when they are not mixed with anything else.
纯净物只含有一种粒子或一种化合物。水、盐和氧气在未与其他物质混合时都是纯净物的例子。
A mixture contains two or more different substances that are not chemically joined together. Each substance in a mixture keeps its own properties. Air is a mixture of nitrogen, oxygen, carbon dioxide and other gases.
混合物含有两种或两种以上没有通过化学键结合的不同物质。混合物中的每种物质都保持自己的性质。空气是氮气、氧气、二氧化碳和其他气体的混合物。
Mixtures can usually be separated by physical methods such as filtration, evaporation, distillation and chromatography. No new substances are formed when a mixture is separated.
混合物通常可以通过过滤、蒸发、蒸馏和色谱等物理方法进行分离。分离混合物时不会生成新的物质。
10. Separating Mixtures | 混合物的分离
Filtration is used to separate an insoluble solid from a liquid. The mixture is poured through filter paper, which allows the liquid to pass through but traps the solid particles.
过滤用于将不溶性固体从液体中分离出来。混合物被倒入滤纸中，滤纸让液体通过，但会截留住固体颗粒。
Evaporation is used to obtain a dissolved solid from a solution. The solution is heated so the solvent evaporates, leaving the solid behind. This works well when the solid does not decompose on heating.
蒸发用于从溶液中获得溶解的固体。加热溶液使溶剂蒸发，留下固体。当固体在加热时不会分解时，这种方法很有效。
Distillation separates a solvent from a solution by boiling the liquid and then condensing the vapour back into a liquid in a cold condenser. This allows the solvent to be collected separately.
蒸馏通过将液体煮沸，然后让蒸气在冷的冷凝管中重新凝结为液体，从而将溶剂从溶液中分离出来。这样就可以单独收集溶剂。
Chromatography can separate coloured substances from a mixture because different substances move at different speeds through a material such as paper.
色谱法可以分离混合物中的有色物质，因为不同物质在纸等材料中移动的速度不同。
11. Conservation of Mass in Physical Changes | 物理变化中的质量守恒
During a physical change, no new substance is formed. The particles themselves do not change, only their arrangement or movement changes. Therefore, the total mass stays the same when a solid melts, a liquid freezes, or a gas condenses.
在物理变化中，没有新物质生成。粒子本身没有改变，只有它们的排列或运动发生了变化。因此，当固体熔化、液体凝固或气体凝结时，总质量保持不变。
For example, if you melt 50 g of ice, you get 50 g of water. If you freeze that water, you get 50 g of ice again. The mass is conserved because no particles are lost or gained.
例如，如果你熔化 50 g 的冰，你会得到 50 g 的水。如果你再把水凝固，你又会得到 50 g 的冰。质量守恒是因为没有粒子损失或增加。
If water evaporates in an open container, the mass of the container appears to decrease. However, the water particles have moved into the air as water vapour. The total mass of the water and the water vapour together is unchanged.
如果水在开放容器中蒸发，容器内物质的质量似乎会减少。但实际上，水粒子已经以水蒸气的形式进入了空气中。水和空气中的水蒸气加在一起的总质量并没有改变。
12. Exam Tips: Describing Particles | 考试技巧：描述粒子
In exams, you need to link what you observe to the particle model. Use precise phrases such as ‘the particles gain energy’, ‘the particles move faster’, ‘the particles move further apart’ and ‘the forces between particles weaken’.
在考试中，你需要把观察到的现象与粒子模型联系起来。使用准确的表述，例如“粒子获得能量”“粒子运动加快”“粒子间距增大”“粒子间的作用力减弱”。
Do not say that the particles themselves melt, boil, expand or contract. The substance melts or boils; the particles change their arrangement and movement.
不要说粒子本身会熔化、沸腾、膨胀或收缩。熔化或沸腾的是物质，粒子改变的是它们的排列方式和运动方式。
When explaining gas pressure, always mention collisions with the container walls. A strong answer might say: ‘Heating the gas gives the particles more kinetic energy, so they collide with the walls more often and with greater force, increasing the pressure.’
在解释气体压强时，一定要提到粒子与容器壁的碰撞。一个完整的答案可以这样写：“加热气体使粒子获得更多动能，因此它们更频繁、更有力地撞击容器壁，压强增大。”
Common mistakes to avoid include saying particles are motionless in solids, saying particles expand when heated, and saying diffusion happens because particles want to spread out. Particles do not ‘want’ anything; they move randomly and spread out because of their motion and available space.
需要避免的常见错误包括：说固体中的粒子是静止不动的；说粒子受热时会膨胀；说扩散发生是因为粒子“想要”扩散。粒子不会“想要”任何东西，它们是无规则运动的，并因为运动和可利用空间而扩散开来。
Published by TutorHao | KS3 Chemistry Revision Series | aleveler.com
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