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.
Besides smelling, touching and looking at the physical appearance of a substance, there are other ways to know for sure what that substance is. This is where chemical properties come in. A chemical property is a property of a substance that is observed when a substance undergoes a chemical change. The chemical change is a type of change that also changes the identity of a substance due to breakage and formation of new chemical bonds, as shown in the figure below: The figure shows a chemical change where two substances, A and B, form and break bonds with each other and other substances, C and D.