Explaining Diffusion | 解释扩散

📚 Explaining Diffusion | 解释扩散

Why can you smell perfume from across a room? Why does ink spread through water without stirring? These everyday observations are explained by diffusion, a process based on the particle model of matter. In this article, you will learn what diffusion is, why it happens, and which factors make it faster or slower.

为什么你能在房间对面闻到香水味？为什么墨水不用搅拌就能在水中散开？这些日常现象都可以用扩散来解释，而扩散基于物质的粒子模型。在本文中，你将学习什么是扩散、它为什么会发生，以及哪些因素会使它变快或变慢。

1. What is diffusion? | 什么是扩散？

Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration. It is a passive process, so it does not require extra energy from a cell or organism.

扩散是粒子从浓度较高的区域向浓度较低的区域发生的净运动。它是一个被动过程，因此不需要细胞或生物体额外提供能量。

Concentration means how crowded the particles are in a space. A high concentration means many particles are packed together; a low concentration means fewer particles are spread out.

浓度表示粒子在空间中的拥挤程度。高浓度意味着许多粒子聚集在一起；低浓度意味着粒子较少且分散。

---

2. Particles are always moving | 粒子总是在运动

All substances are made of tiny particles. In gases and liquids, these particles have kinetic energy and move constantly in random directions. Even when water appears still, its particles are moving.

所有物质都由微小粒子组成。在气体和液体中，这些粒子具有动能，并持续随机运动。即使水看起来很静止，其粒子仍在运动。

This random movement is called Brownian motion. Particles collide with one another and with container walls. Each collision changes their direction, producing an unpredictable zig-zag path.

这种随机运动称为布朗运动。粒子彼此碰撞并与容器壁碰撞。每次碰撞都会改变它们的方向，产生不可预测的锯齿形路径。

---

3. The idea of net movement | 净运动的概念

Because particles move randomly in all directions, why is there an overall movement? The answer is probability. If one area has many particles and another area has few, it is more likely that particles move from the crowded area to the empty area than the other way round.

由于粒子朝各个方向随机运动，为什么会有整体运动？答案是概率。如果一个区域粒子很多，另一个区域粒子很少，那么粒子从拥挤区域向空旷区域移动的可能性比反向移动更大。

This overall movement is called net movement. It continues until the particles are evenly mixed. At that point the concentration is equal throughout, which is called equilibrium. Particles do not stop moving at equilibrium; there is just no further net change.

这种整体运动称为净运动。它会持续到粒子均匀混合。此时各处浓度相等，称为平衡。达到平衡时粒子并不会停止运动，只是不再有进一步的净变化。

---

4. Concentration gradient | 浓度梯度

A concentration gradient is the difference in concentration between two neighbouring regions. When one area has a much higher concentration than another, the gradient is steep.

浓度梯度是两个相邻区域之间的浓度差。当一个区域的浓度远高于另一个区域时，梯度就陡。

Diffusion always occurs down the concentration gradient, from high to low. The steeper the gradient, the greater the difference in concentration, so the faster the particles diffuse.

扩散总是沿着浓度梯度进行，从高浓度到低浓度。梯度越陡，浓度差越大，粒子扩散得越快。

Think of a ball rolling down a hill. A steep hill provides a larger driving force for the ball. In diffusion, a steep concentration gradient provides a larger driving force for net particle movement.

想象一个球从山坡上滚下。陡坡为球提供更大的驱动力。在扩散中，陡峭的浓度梯度为粒子的净运动提供更大的驱动力。

---

5. Diffusion in gases | 气体中的扩散

Diffusion is fastest in gases. Gas particles are far apart and have large spaces between them. They also move at high speeds. This means gas particles can spread quickly through other gas particles.

扩散在气体中最快。气体粒子相距很远，之间有很大的空间。它们还以高速运动。这意味着气体粒子可以迅速地在其他气体粒子中扩散。

When you open a bottle of perfume, the liquid evaporates and gas particles enter the air. They diffuse across the room, so someone far away can soon smell the scent.

当你打开一瓶香水时，液体蒸发，气体粒子进入空气。它们扩散到整个房间，因此远处的人很快就能闻到香味。

The smell of cooking also travels by diffusion. Vapour particles from hot food move through the air and reach your nose, often before you enter the kitchen.

烹饪食物的气味也是通过扩散传播的。热食物的蒸气粒子在空气中移动，并在你进入厨房之前就到达你的鼻子。

---

6. Diffusion in liquids | 液体中的扩散

Diffusion in liquids is slower than in gases. Liquid particles are close together and move more slowly. They have less space to move, so they collide more frequently and change direction often.

液体中的扩散比气体中慢。液体粒子彼此靠近

Published by TutorHao | KS3 Chemistry Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）