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.
Need more? Chemical changes are the basis for chemical reactions. Here is a list of 10 chemical reactions in everyday life. Less-familiar chemical reactions are also examples of chemical changes. While it's not always easy to tell a chemical change has occurred, there are some telltale signs. Chemical changes may cause a substance to change color, change temperature, produce bubbles, or (in liquids) produce a precipitate. Chemical changes can also be considered to be any phenomenon that allows a scientist to measure chemical properties.