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 is a dissociation, recombination, or rearrangement of atoms. compound Compare with element and mixture. A compound is a material formed from elements chemically combined in definite proportions by mass. For example, water is formed from chemically bound hydrogen and oxygen.ompare with molecule and ion. An atom is the smallest particle of an element that retains the chemical properties of the element. Atoms are electrically neutral, with a positively charged nucleus that binds one or more electrons in motion around it.