Science 101: Why Baking a Cake Doesn’t Represent a Physical Change
While it may not seem like it on the surface, when you bake a cake, you are practicing chemistry. When you place your ingredients in the oven, the batter changes from a liquid to a fluffy yet solid cake. At first glance, many people think this is a physical change, but it is a chemical change. Understanding the differences between chemical and physical changes helps provide a foundation for science and chemistry.
What Is a Physical Change?
A physical change occurs when you change the way something looks without altering its composition. All of the bonds between the atoms remain intact. While the substance may look different, its chemical makeup remains the same.
How to Tell That a Chemical Change Took Place
There are a few indicators that you can look out for to tell that a chemical reaction took place:
- Change in color
- Change in temperature
- Formation of a precipitate
- Formation of gas
- Giving off light
When you bake a cake, you may notice that the color changes (darkens) during the baking process. There is also a change in temperature, and the ingredients release gas bubbles to make a fluffy cake. All of these indicate that a chemical change has taken place.
Examples of a Chemical Change
Chemical changes cannot be reversed. Once you bake the cake, you can't lower the temperature and turn it back into the original ingredients. Other examples of processes that cannot be reversed and indicate a chemical change include:
- Metal rusting
- Wood burning
- Milk curdling
- Cooking an egg
Examples of a Physical Change
During a physical change, the substance remains the same. It just has a different form or appearance, such as a change in shape, color, or form. Examples include:
- Tearing up a piece of paper
- Shattering a glass
- Melting ice cubes
- Boiling water
In all of these instances, the chemical composition of each substance remains intact. Glass is still glass once it shatters. Water is still water, no matter if it is frozen or evaporated into steam.
How to Tell the Difference Between Chemical and Physical Changes
It is not always easy to tell the difference between the two types of changes. Chemical changes take place on a molecular level, and you can't observe the bonds between the atoms with the naked eye. In some instances, you have to perform an in-depth analysis to tell what kind of change occurred. However, if only the appearance changed, and you can recover your original ingredients, a physical change likely occurred.