5.5.2 Gas Pressure and Boyle’s Law | 5.5.2 气体压强与玻意耳定律

📚 5.5.2 Gas Pressure and Boyle’s Law | 5.5.2 气体压强与玻意耳定律

Gas pressure is a fundamental concept in the IGCSE Edexcel Science curriculum. This revision guide explains how gas particles create pressure, how pressure changes with volume, and how to use Boyle’s law to solve exam-style problems. You will also see common misconceptions and practical tips for achieving full marks.

气体压强是IGCSE Edexcel科学课程的基础概念。本复习指南解释气体粒子如何产生压强、压强如何随体积变化，以及如何运用玻意耳定律解决考试型题目。你还会看到常见错误和获取满分的实用技巧。

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1. Introduction to Gas Pressure | 气体压强简介

Gas pressure is the force exerted by a gas on the walls of its container, divided by the area of the wall. It is measured in pascals (Pa) or newtons per square metre (N/m²). For a gas sealed in a syringe, pressure can be recorded in kilopascals (kPa).

气体压强是气体对其容器壁所施加的力除以器壁面积。单位是帕斯卡（Pa）或牛顿每平方米（N/m²）。对于密封在注射器中的气体，压强可以用千帕（kPa）记录。

The pressure of a gas is caused by billions of tiny particles moving rapidly and colliding with the container walls. Each collision exerts a small push, and the total push over an area is what we measure as pressure.

气体压强由数十亿个快速运动的微小粒子与容器壁碰撞而产生。每次碰撞都施加一个微小的推力，而单位面积上的总推力就是我们测量的压强。

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2. The Particle Model of a Gas | 气体的粒子模型

In a gas, particles are far apart, move randomly, and travel at high speeds. They have weak forces of attraction between them, so they are free to spread out and fill any container completely.

在气体中，粒子间距很大，运动随机且高速。粒子之间的吸引力很弱，因此它们可以自由扩散并完全充满任何容器。

Compared with solids and liquids, gas particles have much more kinetic energy. The higher the temperature, the faster the particles move, and the stronger the collisions with the container walls.

与固体和液体相比，气体粒子具有更大的动能。温度越高，粒子运动越快，与容器壁的碰撞就越猛烈。

• Gas particles are in constant random motion.

  气体粒子处于永不停息的随机运动中。

• Gas particles collide elastically with the walls.

  气体粒子与容器壁发生弹性碰撞。

• The distance between gas particles is much greater than their diameter.

  气体粒子之间的距离远大于其直径。

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3. How Gas Particles Create Pressure | 气体粒子如何产生压强

When a gas particle hits a container wall, it changes direction and rebounds. This reversal of motion requires a force, and according to Newton’s third law, the wall feels an equal and opposite push. Millions of these collisions per second create a steady pressure on the wall.

当气体粒子撞击容器壁时，它会改变方向并反弹。这种运动反向需要力，而根据牛顿第三定律，器壁受到一个等大反向的推力。每秒数百万次这样的碰撞在器壁上形成稳定的压强。

The pressure depends on two factors: how often particles hit the walls, and how hard each hit is. If you pump more gas into the same container, more particles per unit volume leads to more collisions and a higher pressure.

压强取决于两个因素：粒子撞击器壁的频率以及每次撞击的猛烈程度。如果你向同一容器内泵入更多气体，单位体积内粒子增多，碰撞更频繁，压强就更高。

Pressure ∝ number of collisions per second

压强 ∝ 每秒碰撞次数

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4. Factors Affecting Gas Pressure | 影响气体压强的因素

For a fixed amount of gas inside a sealed container, two main factors affect pressure: temperature and volume. Increasing temperature gives particles more kinetic energy, so they move faster, hit walls harder and more often. This raises pressure if volume stays constant.

对于密封容器内固定量的气体，两个主要因素影响压强：温度和体积。升高温度使粒子获得更大动能，运动更快，撞击更猛烈、更频繁。如果体积不变，压强就会升高。

If temperature stays constant, decreasing the volume squeezes particles into a smaller space. Particles now travel shorter distances between wall hits, so they collide with the walls more frequently. Pressure therefore increases.

如果温度不变，减小体积会将粒子挤压到更小的空间。粒子在两次撞击之间运动的距离变短，因此与器壁碰撞更频繁，压强随之增大。

Change	Effect on pressure (constant T)
Volume increases	Pressure decreases
Volume decreases	Pressure increases
Temperature increases (constant V)	Pressure increases

体积增大 → 压强减小 (恒温)

体积减小 → 压强增大 (恒温)

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5. Boyle’s Law: Pressure and Volume | 玻意耳定律：压强与体积

Boyle’s law describes the relationship between pressure and volume for a fixed mass of gas kept at constant temperature. It states that for a fixed mass of gas at constant temperature, the pressure of the gas is inversely proportional to its volume.

玻意耳定律描述一定质量的气体在温度保持恒定时的压强与体积关系。它指出：在温度恒定时，一定质量气体的压强与其体积成反比。

This means that if you halve the volume, the pressure doubles; if you double the volume, the pressure halves. The product of pressure and volume remains constant as long as temperature and mass do not change.

这意味着，若体积减半，则压强加倍；若体积加倍，则压强减半。只要温度和气体质量不变，压强和体积的乘积保持不变。

P ∝ 1/V (at constant T and fixed mass)

P ∝ 1/V（在恒定温度和固定气体质量下）

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6. The Equation of Boyle’s Law | 玻意耳定律的方程

Boyle’s law can be written using an equation. If a gas changes from an initial pressure P₁ and volume V₁ to a final pressure P₂ and volume V₂, then the following relationship is true.

玻意耳定律可以用方程表示。若气体从初始压强P₁和体积V₁变为最终压强P₂和体积V₂，则下列关系成立。

P₁V₁ = P₂V₂

In this equation, pressure must be in the same unit on both sides (for example, kPa), and volume must also be in the same unit on both sides (for example, cm³ or m³). You do not need to convert to standard units as long as the units match.

在这个方程中，等号两边压强必须使用相同单位（例如kPa），体积也必须使用相同单位（例如cm³或m³）。只要单位一致，就不需要转换为国际标准单位。

It is essential to remember that this equation only works when temperature and gas mass are constant. If the problem says the gas is ‘heated’ or ‘cooled’, Boyle’s law cannot be used.Published by TutorHao | IGCSE Science Revision Series | aleveler.com

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