📚 States of Matter KS3 CIE Answers | KS3 CIE 物质状态答案解析
This revision guide gives clear, exam-style answers for the KS3 CIE topic 'States of Matter'. It covers the particle model, properties of solids, liquids and gases, changes of state, diffusion, gas pressure and density. Use the paired explanations to check your understanding before a test.
本复习指南针对 KS3 CIE 的 '物质状态' 主题，给出清晰的考试风格答案。内容涵盖粒子模型、固体液体气体的性质、状态变化、扩散、气体压强和密度。使用中英配对解释，在考试前检查你的理解。
1. What are the three states of matter? | 物质的三态是什么？
The three common states of matter are solid, liquid and gas. The state depends on how strongly the particles are held together and how much energy they have.
物质的三种常见状态是固体、液体和气体。物质处于哪种状态取决于粒子之间的结合力有多强，以及粒子具有多少能量。
For example, water exists as ice (solid), liquid water and steam (gas). The chemical formula H₂O stays the same in all three states.
例如，水可以以冰（固体）、液态水和蒸汽（气体）的形式存在。在这三种状态中，化学式 H₂O 保持不变。
2. How does the particle model explain solids? | 粒子模型如何解释固体？
In a solid, particles are packed closely in a fixed, regular arrangement. They vibrate around fixed positions but do not move from place to place.
在固体中，粒子紧密排列，形成固定且规则的排列方式。它们在固定位置附近振动，但不会从一个位置移动到另一个位置。
This is why a solid has a fixed shape and a fixed volume. It cannot be compressed because the particles are already very close together.
这就是固体具有固定形状和固定体积的原因。固体不能被压缩，因为粒子已经非常紧密地靠在一起。
3. How does the particle model explain liquids? | 粒子模型如何解释液体？
In a liquid, particles are still close together but are arranged irregularly. They can slide past each other, so a liquid can flow.
在液体中，粒子仍然彼此靠近，但排列不规则。它们可以相互滑动，因此液体能够流动。
A liquid has a fixed volume but takes the shape of the bottom of its container. It cannot be compressed easily because particles remain close.
液体具有固定的体积，但会呈现容器底部的形状。液体不容易被压缩，因为粒子仍然彼此靠近。
4. How does the particle model explain gases? | 粒子模型如何解释气体？
In a gas, particles are far apart and move quickly in all directions. They have much more energy than particles in solids or liquids.
在气体中，粒子相距很远，并向各个方向快速运动。它们比固体或液体中的粒子具有更多的能量。
A gas has no fixed shape and no fixed volume. It spreads out to fill its container and can be compressed because there is a lot of space between particles.
气体没有固定的形状，也没有固定的体积。它会扩散并充满整个容器，并且可以被压缩，因为粒子之间存在大量空间。
5. What happens during changes of state? | 状态变化时会发生什么？
Melting is solid to liquid, freezing is liquid to solid, boiling and evaporation are liquid to gas, and condensation is gas to liquid. Sublimation is solid directly to gas.
熔化是固体变为液体，凝固是液体变为固体，沸腾和蒸发是液体变为气体，冷凝是气体变为液体。升华是固体直接变为气体。
During a change of state, the temperature stays constant while the substance is melting or boiling. Energy is used to break forces between particles rather than to raise temperature.
在状态变化过程中，物质正在熔化或沸腾时，温度保持不变。能量被用来打破粒子之间的作用力，而不是用来升高温度。
6. How do you read a heating curve? | 如何解读加热曲线？
A heating curve shows temperature rising as a solid is heated. The graph has flat sections during melting and boiling because the temperature does not change while the state changes.
加热曲线显示固体被加热时温度上升的情况。曲线在熔化和沸腾期间出现水平段，因为状态变化时温度不发生变化。
For water at standard pressure, melting occurs at 0 °C and boiling at 100 °C. The flat line at 0 °C shows ice turning to water; the flat line at 100 °C shows water turning to steam.
对于标准压力下的水，熔化发生在 0 °C，沸腾发生在 100 °C。0 °C 处的水平线表示冰变成水；100 °C 处的水平线表示水变成蒸汽。
7. What is diffusion? | 什么是扩散？
Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration. It happens because particles move randomly.
扩散是粒子从浓度较高的区域向浓度较低的区域扩散的过程。它之所以发生，是因为粒子进行无规则运动。
Diffusion is fastest in gases, slower in liquids and does not happen in solids because particles cannot move past each other. An example is perfume smell spreading across a room.
扩散在气体中最快，在液体中较慢，在固体中不会发生，因为固体中的粒子不能相互滑过。一个例子是香水的气味在房间中扩散。
8. Why do gases exert pressure? | 气体为什么会产生压强？
Gas pressure is caused by gas particles colliding with the walls of their container. Each collision exerts a tiny force; many collisions per second create measurable pressure.
气体压强是由气体粒子与容器壁碰撞引起的。每次碰撞都会产生一个微小的力；每秒许多次碰撞就会产生可测量的压强。
If a gas is heated in a sealed container, the particles move faster and hit the walls harder and more often, so the pressure increases. If the volume is increased, the pressure decreases.
如果气体在密封容器中被加热，粒子运动加快，更剧烈、更频繁地撞击容器壁，因此压强增大。如果体积增大，压强就会减小。
9. What is density and how is it calculated? | 什么是密度？如何计算？
Density is mass per unit volume. The formula is:
密度是每单位体积的质量。公式为：
density = mass ÷ volume
密度 = 质量 ÷ 体积
The unit is g/cm³ or kg/m³. For example, a block with mass 100 g and volume 20 cm³ has a density of 5 g/cm³.
单位是 g/cm³ 或 kg/m³。例如，一个质量为 100 g、体积为 20 cm³ 的物块密度为 5 g/cm³。
10. Exam-style model answers | 考试风格模型答案
Question 1: Explain why a gas can be compressed but a solid cannot.
问题 1：解释为什么气体可以被压缩而固体不能。
Answer: In a gas, particles are far apart with large spaces between them, so they can be pushed closer together. In a solid, particles are already touching and closely packed, so there is no space to compress them further.
答案：气体中粒子相距很远，粒子间有较大空间，因此可以被推近。固体中粒子已经紧密接触，没有进一步压缩的空间。
Question 2: Describe what happens to particles when ice melts.
问题 2：描述冰熔化时粒子会发生什么变化。
Answer: The particles gain energy and vibrate more. The regular solid structure breaks down, and the particles can slide past each other, forming liquid water. The temperature stays at 0 °C during melting.
答案：粒子获得能量，振动加剧。规则的固体结构被破坏，粒子可以相互滑动，形成液态水。熔化过程中温度保持在 0 °C。
11. Common misconceptions to avoid | 需要避免的常见误区
Misconception 1: 'Particles expand when heated.' The correct idea is that the spaces between particles increase, but the particles themselves do not get bigger.
误区 1：'粒子受热会膨胀。' 正确的理解是粒子之间的空隙增大，但粒子本身不会变大。
Misconception 2: 'Melting and dissolving are the same.' Melting is a change of state caused by heat; dissolving is a physical mixing of a solute into a solvent, and no new state change is needed.
误区 2：'熔化和溶解是一回事。' 熔化是由加热引起的状态变化；溶解是溶质与溶剂的物理混合，不涉及新的状态变化。
Misconception 3: 'Air is one pure substance.' Air is a mixture of gases, mainly nitrogen and oxygen, with small amounts of carbon dioxide, argon and water vapour.
误区 3：'空气是一种纯净物。' 空气是气体混合物，主要成分是氮气和氧气，还含有少量的二氧化碳、氩气和水蒸气。
12. Quick quiz with answers | 快速测验及答案
1. Which state has a fixed volume but no fixed shape? Answer: liquid.
1. 哪种状态具有固定体积但没有固定形状？答案：液体。
2. Name the process when a gas turns into a liquid. Answer: condensation.
2. 气体变成液体的过程叫什么？答案：冷凝。
3. What happens to diffusion rate when temperature increases? Answer: It increases because particles move faster.
3. 温度升高时，扩散速率会怎样？答案：扩散速率增大，因为粒子运动更快。
4. Calculate the density if mass = 60 g and volume = 12 cm³. Answer: 60 ÷ 12 = 5 g/cm³.
4. 如果质量 = 60 g，体积 = 12 cm³，计算密度。答案：60 ÷ 12 = 5 g/cm³。
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