📚 KS3 Year 8 Matter: Particles, States and Separation | KS3 八年级物质：粒子、状态与分离
Matter is everything around us that has mass and takes up space. In Year 8, you will use the particle model to explain why solids, liquids and gases behave differently, and how mixtures can be separated.
物质是我们周围一切具有质量并占据空间的东西。在八年级，你将使用粒子模型来解释为什么固体、液体和气体的行为不同，以及如何分离混合物。
1. What is Matter? | 什么是物质？
Matter is defined as anything that has mass and volume. Mass is measured in kilograms (kg) and volume in cubic metres (m³) or litres (L).
物质被定义为任何具有质量和体积的东西。质量以千克（kg）为单位，体积以立方米（m³）或升（L）为单位。
Matter exists in three common states on Earth: solid, liquid and gas. All materials you see, touch and use are made of matter.
地球上物质通常以三种状态存在：固态、液态和气态。你看到、触摸和使用的所有材料都由物质组成。
Energy is not matter because it has no mass and does not occupy space. Sound, light and heat are forms of energy, not matter.
能量不是物质，因为它没有质量，也不占据空间。声、光和热都是能量的形式，而不是物质。
2. The Particle Model of Matter | 物质的粒子模型
The particle model states that all matter is made of tiny particles. These particles are far too small to see, even with a light microscope.
粒子模型指出，所有物质都是由微小的粒子组成的。这些粒子小到即使使用光学显微镜也无法看到。
There are four key ideas: particles are always moving; there are spaces between particles; particles attract each other; and the speed of particles increases with temperature.
有四个关键观点：粒子总是在运动；粒子之间存在空隙；粒子相互吸引；粒子的速度随温度升高而加快。
The particle model is a scientific model. It helps us explain observations such as expansion, compression and changes of state.
粒子模型是一种科学模型。它帮助我们解释膨胀、压缩和状态变化等观察结果。
3. States of Matter: Solid, Liquid and Gas | 物质的三态：固态、液态和气态
In a solid, particles are packed closely in a regular pattern. They vibrate about fixed positions and cannot move freely, so solids have a fixed shape and volume.
在固体中，粒子紧密排列成规则的结构。它们在固定位置附近振动，不能自由移动，因此固体具有固定的形状和体积。
In a liquid, particles are close together but arranged irregularly. They can slide past each other, so liquids have a fixed volume but take the shape of the container.
在液体中，粒子彼此靠近但排列不规则。它们可以相互滑动，因此液体具有固定的体积，但形状随容器而变化。
In a gas, particles are far apart and move rapidly in all directions. Gases have no fixed shape or volume; they spread out to fill any container.
在气体中，粒子相距很远并朝各个方向快速运动。气体没有固定的形状或体积；它们会扩散充满任何容器。
| Property / 性质 | Solid / 固体 | Liquid / 液体 | Gas / 气体 |
|---|---|---|---|
| Shape / 形状 | Fixed / 固定 | Takes shape of container / 随容器形状 | Fills container / 充满容器 |
| Volume / 体积 | Fixed / 固定 | Fixed / 固定 | Not fixed / 不固定 |
| Particle arrangement / 粒子排列 | Regular and touching / 规则且接触 | Random and close / 随机且紧密 | Far apart / 相距很远 |
| Particle movement / 粒子运动 | Vibrate only / 仅振动 | Slide past each other / 相互滑动 | Move freely and fast / 自由快速运动 |
4. Changing State: Melting, Freezing, Boiling and Condensing | 状态变化：熔化、凝固、沸腾和冷凝
Melting is the change from solid to liquid. It happens at the melting point when particles gain enough energy to break free from their fixed positions.
熔化是从固态到液态的变化。它发生在熔点时，粒子获得足够的能量摆脱固定位置。
Freezing is the reverse change from liquid to solid. Particles lose energy and become locked into a regular pattern.
凝固是从液态到固态的相反变化。粒子失去能量并锁定成规则的结构。
Boiling and evaporation both change liquid to gas, but boiling occurs throughout the liquid at the boiling point, while evaporation occurs only at the surface and at any temperature.
沸腾和蒸发都能使液体变为气体，但沸腾在沸点时于整个液体内发生，而蒸发只在表面并且在任何温度下都可发生。
Condensation is the change from gas to liquid. It occurs when gas particles lose energy and come closer together.
冷凝是从气态到液态的变化。当气体粒子失去能量并彼此靠近时发生。
Sublimation is a less common change from solid directly to gas, such as solid carbon dioxide ('dry ice').
升华是较不常见的直接从固态到气态的变化，例如固态二氧化碳（'干冰'）。
5. Diffusion and Particle Movement | 扩散与粒子运动
Diffusion is the spreading of particles from a region of higher concentration to a region of lower concentration. It is evidence that particles are constantly moving.
扩散是粒子从浓度较高的区域向浓度较低的区域扩散。它证明了粒子在不断地运动。
Diffusion is fastest in gases, slower in liquids and extremely slow in solids because particle movement is most free in gases.
扩散在气体中最快，在液体中较慢，在固体中极慢，因为气体中的粒子运动最自由。
Increasing temperature increases the rate of diffusion because particles move faster when they have more kinetic energy.
升高温度会加快扩散速率，因为粒子获得更多动能后运动得更快。
A common example is the smell of perfume spreading across a room. The perfume particles collide with air particles and gradually move further apart.
一个常见的例子是香水的气味在房间里扩散。香水粒子与空气粒子碰撞，逐渐移动得更远。
6. Density and the Particle Model | 密度与粒子模型
Density is the mass of a substance per unit volume. It tells us how tightly packed the particles are.
密度是物质单位体积的质量。它告诉我们粒子的排列紧密程度。
ρ = m ÷ V
Most solids have high density because their particles are closely packed. Gases have very low density because particles are far apart.
大多数固体密度高，因为它们的粒子排列紧密。气体密度非常低，因为粒子相距很远。
Ice floats on water because ice is less dense than liquid water. This unusual property is due to the open lattice structure of ice particles.
冰浮在水面上是因为冰的密度小于液态水。这种不寻常的性质是由于冰粒子的开放晶格结构。
You can calculate density using mass in grams (g) and volume in cubic centimetres (cm³), giving density in g/cm³.
你可以用质量（克，g）和体积（立方厘米，cm³）计算密度，得到密度的单位为 g/cm³。
7. Pressure in Gases | 气体压强
Gas pressure is caused by millions of gas particles colliding with the walls of their container. Each collision produces a tiny force.
气体压强是由数百万气体粒子撞击容器壁引起的。每次碰撞都产生一个微小的力。
If the volume of a fixed amount of gas decreases at constant temperature, the particles collide with the walls more often, so pressure increases.
如果在恒定温度下固定量气体的体积减小，粒子与壁碰撞得更频繁，因此压强增大。
If the temperature of a gas increases at constant volume, particles move faster and strike the walls harder and more often, increasing pressure.
如果在恒定体积下气体温度升高，粒子运动更快，更猛烈、更频繁地撞击壁，使压强增大。
This explains why aerosol cans warn against heating: the pressure inside can rise dangerously.
这就解释了为什么气雾罐警告不要加热：内部的压强会危险地升高。
8. Pure Substances and Mixtures | 纯净物与混合物
A pure substance contains only one type of particle or one type of atom, element or compound. It has a
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