Here's why:
* Entropy: The second law of thermodynamics states that the total entropy of a closed system always increases over time. In simpler terms, systems tend to move from order to disorder.
* Random Motion: Molecules are constantly in random motion, colliding with each other.
* Concentration Gradient: When there's a high concentration of molecules in one area and a low concentration in another, there are more collisions on the high concentration side, pushing molecules towards the low concentration area.
* Equal Distribution: Diffusion continues until the molecules are evenly distributed throughout the space, maximizing entropy and minimizing the concentration gradient.
Example: Imagine a drop of food coloring in a glass of water. The dye molecules are initially concentrated in the drop. They will naturally diffuse outwards, spreading throughout the water until the color is evenly distributed.
Note: While diffusion doesn't require energy input, it can be influenced by factors like temperature (higher temperature = faster diffusion) and the size and type of molecules.
