1. Observable Diffusion
Some substances are easy to observe through diffusion, such as a drop of food coloring in a cup of water, or a spritz of perfume filling the air. Some diffusion is a fast process, and sometimes the diffusion is present but much less noticeable due to variations in temperature; a tea bag dropped in a cup of hot water will diffuse much faster and change the water's color quickly, whereas that same tea bag dropped in a cup of cold water will take longer to diffuse noticeably.
2. Heat Conduction
Heat conduction, the process by which heat transfers between two objects, is actually an example of diffusion. In conduction, the heat energy always moves from an area of high temperature to an area of low temperature. This can be seen as moving from a high concentration to low concentration, which occurs in diffusion.
3. Lattice Model
In chemistry, the lattice model for diffusion is used to explain how atoms move through a crystalline lattice structure. These objects move about through the lattice by one of several different types of diffusion, but basically they can jump from point to point through the crystalline structure into areas of lower concentration.
4. Alloy Production
Alloys are formed when two or more types of metal are combined to form a new substance. For example, steel is formed when iron, carbon, aluminum, and other trace metals are combined. Once these metals come together, they are not easily separated. Diffusion occurs when the particles of the components spread out and combine from areas of high concentration to lower concentration.
5. Flat Soda and Pasta
Diffusion occurs in the kitchen as well. Upon opening a bottle of soda, the CO2 that forms the bubbly effect begins to disperse into the surrounding air. If left open, the bottle of soda will become flat; even if the bottle is closed, over time the CO2 will diffuse out through the unsealed bottle cap. Diffusion also occurs when cooking pasta, as the boiling water diffuses into the dried noodles, rehydrating them and making them plumper and saturated.