扩散的原理
How Diffusion Works
将扩散解释为微粒从高浓度区域向低浓度区域的净移动，并描述它在细胞内及细胞间运输物质（如氧气、二氧化碳、葡萄糖）中的作用。
Explain diffusion as the net movement of particles from a region of higher concentration to lower concentration, and describe its role in moving materials (oxygen, carbon dioxide, glucose) in and between cells
学习证据 / Evidence
- 用微粒理论定义扩散
- 解释氧气和二氧化碳在肺泡处的扩散方向
- 解释细胞如何通过扩散从血液中获取葡萄糖
- 识别影响扩散速率的因素（浓度梯度、表面积、距离）
- Defines diffusion using particle theory
- Explains the direction of diffusion of oxygen and carbon dioxide at the alveoli
- Explains how cells get glucose from the blood using diffusion
- Identifies factors that affect the rate of diffusion (concentration gradient, surface area, distance)
评估问题 / Assessment
如果问{{name}}为什么氧气不需要身体泵送就能从肺部进入血液，他们能否解释什么是扩散，以及为什么扩散总是朝一个方向移动？
If {{name}} was asked why oxygen moves from the lungs into the blood without the body needing to pump it, could they explain what diffusion is and why it always moves in one particular direction?