While you may never have heard of Ostwald ripening by its name, there’s a good chance you’ve enjoyed food that was created using it. Ostwald ripening is a phenomonon that can occur in liquids and solids that changes their structure over time. If you’ve ever let your ice cream warm up instead of digging at it with an ice cream scoop, you’ve probably seen Ostwald ripening in action the next time you took that ice cream out of the freezer and found it was crunchier than it should have been. Here is what you should know about Ostwald ripening.
Who Is Ostwald Ripening Named After?
Given the attention-grabbing name of this particular process, it’s worth taking the time to address that first. Similar to numerous other scientific terms, the term Ostwald ripening came to be because of the person responsible for discovering it. The phenomenon in question was first documented back in 1896 by Baltic German chemist Friedrich Wilhelm Ostwald. Ostwald is a renowned figure in the world of physical chemistry, and he is among the scientists considered to be the modern founders of the aforementioned field.
Over the course of his scientific career, Ostwald tallied numerous significant accomplishments beyond documenting the eponymous phenomenon at the heart of this article. He also engineered the Ostwald process that is used to make nitric acid. He also worked closely on catalysis, chemical equilibria, and reaction velocities. Ostwald was awarded the Nobel Prize in Chemistry for the work he did on those subjects.
What Is Ostwald Ripening?
Moving back to Ostwald ripening, it is a phenomenon that can impact both solid and liquid solutions. Once it takes place, the structure of the solution itself can change quite noticeably. When a solution undergoes Ostwald ripening, what happens is that the smaller particles present effectively give way to larger particles. The larger particles are able to increase their size by drawing from the smaller particles, and the smaller particles will decrease in size further as they go through Ostwald ripening.
What Causes Ostwald Ripening to Take Place?
Ostwald ripening is a process that is driven by thermodynamics. The process, which is also sometimes referred to as particle coarsening, takes place because of how particles in the solution behave. A prime reason for why Ostwald ripening occurs is due to larger particles featuring greater stability compared to their smaller counterparts. The smaller particles tend to be the ones found on the surface. Inside the solution, the particles are packed together better and aligned in a more orderly fashion, and they are also larger.
As the solution matures and undergoes changes, the larger particles inside will remain in place while the smaller particles start to detach themselves from the surface. After being detached, the smaller particles previously on the surface can now make their way to the larger particles. At the end of the process, the results will show that the interior particles have grown significantly larger and the smaller ones have shrunk further.
What Are Some Examples of Ostwald Ripening Happening in the Real World?
Arguably the most notable example of Ostwald ripening that people encounter on a regular basis involves ice cream. The texture of ice cream can change depending on how many times it has been frozen. The first time the ice cream is taken out of the freezer and consumed, it is still likely to have a smooth and creamy texture, but if that ice cream is left to melt for some time before being returned to the freezer, its texture will be different the next time it is eaten.
Specifically, the texture of the re-frozen ice cream will be grittier. This is why you’re better off using a heated ice cream scoop to serve your ice cream than by waiting for the ice cream to melt and soften up. It can also occur when you’re making ice cream with an ice cream maker and don’t put the ice cream into the freezer fast enough. Because of this, countertop ice cream makers that stay cold on their own can be a better option if you’re picky about ice cream texture.
Other examples of Ostwald ripening include:
- The ouzo effect, which takes place when water is added to an anise-flavored spirit
- Larger drops emerging from rain clouds
- Formation of certain igneous rocks
Ostwald ripening is a fascinating process to monitor and it is also important to understand further as it is essential to the development of important technologies such as quantum dots.