The highest level of scientific experiment is known as experimental, or randomized control. In this type, as the name implies, there is the greatest amount of control. There are at least two groups used in this type of scientific experiment. Each group is made up of subjects that resemble each other as close as possible, such as by age, gender, etc. Subjects can be human, animal or the environment.
Chemical changes can result from the combination of different substance through a reaction to give one or more different substances. Decomposition, the opposite of combination, involves the breakdown of a single substance into two or more different substances.
A chemical change occurs when a new substance is formed through a chemical reaction like when fruit ripens or rots. When something undergoes a chemical reaction and a new substance is formed as a result, we call this chemical change. In some instances, simply applying heat can cause a chemical change. Cooking pancakes, for instance, is an example of a chemical change; the pancake batter changes from a liquid to a solid. Rust forming on metal is another example of a chemical change. The iron reacts with water and oxygen to create a new substance â rust.