So chemical changes. Chemical changes are changes in the chemical composition that create a new chemical bond or bonds and product or products. Basically, a chemical change changes the identity of your original substance. Some common types of chemical changes involve the rusting of metals. The example that we had above of iron rusting or old cars rusting is a prime example of a chemical change. The metal is transformed into a metal oxide by reacting with the oxygen in the air.

Next, we have the burning of materials. So if you're burning, baking, or cooking, you're breaking down old bonds and creating new connections, thereby changing the identity of your original substance. Next, we have the metabolism of food. When you're eating food, it goes through your digestive tract, your body absorbs nutrients, and it becomes something completely different.

Next, chemical reactions. Chemical reactions involve our original substance undergoing some new chemical changes to create chemical bonds. And then finally, the last two, we can visually see, and that is when we have a color change. A substance might be clear and then it changes to blue or a color that we can see, or an odor change. Something might smell great and then undergoes a chemical reaction and it becomes horrible in terms of smell, or it could smell really bad and it undergoes a chemical change and starts smelling okay or loses its smell altogether. Remember, a chemical change is basically changing the identity of a substance by changing its chemical bonds and connections.