Throughout our lives, there are many objects whose shape, size and texture are always changing. There are two main types of changes with regards to the alteration of certain objects, one of them is called a chemical change whereas the other one is called a physical change. A very good example of a chemical change that will aid in the understanding of what it is occurs every year on the fourth of July.
To celebrate the independence of its state, some people of the United States of America explode fireworks. Fireworks are a very good example of what we call a chemical change. Basically, a chemical change can be best described as a change in a substance through which the composition of that very substance is changed completely. Or, to better put it, a chemical change occurs when there is a change of one substance to a completely different second one. Let’s get into the details of what exactly happens in a chemical change.
When a chemical change occurs, the color of the initial substance changes, take for example the leaves that change their color when there is a transition from summer to autumn. Also, have you ever noticed that when you bite on an apple and leave it there for a few minutes, the color of the eaten area changes? Well, that is another chemical change.
Another classic sign of a chemical change is when there is a transfer of energy, which is either taken in or released. The best example of this is when we are in the process of baking a cake. Another example is when a firecracker erupts, there is a transfer of energy in the form of light which is released.
Finally, a chemical change is also known to occur when the odor or the smell of a substance changes, or when a process involves the release of a certain gas or the production of another solid. For example, a chemical change occurs when food spoils. Take a rotten egg and a normal egg, you will notice that the smells of both these foods are much different because the rotten egg smells very bad compared to the normal egg, thus a chemical change has occurred.
The main difference between a chemical change and a physical change is that when a chemical change occurs we can’t reverse the process. Whereas, in a physical change we can easily reverse the process. For example when we freeze water into ice we can easily obtain the water back by unfreezing the water. This is what the main difference is between a physical change and a chemical change.
Source:
http://www.ric.edu/faculty/ptiskus/chemical/
