This changes the form of matter, but does not change the original substance into another substance. What is this?

Expert Answers
dcbiostat eNotes educator| Certified Educator

Physical changes may change the form of a substance. However, physical changes do not change the composition of the substance. Thus, no new substances are made during physical changes.

Examples of physical changes are smashing, tearing, and mixing. Additionally, all phase changes are physical changes. An example of a phase change is liquid water freezing. During a phase change, energy is added or removed. When energy is added, the molecules begin to move faster and apart. When energy is removed, the molecules begin to slow down and come closer to one another. Although the distance between the molecules may change during a phase change, the composition of each molecule remains the same.

On the other hand, chemical changes can change both the appearance and chemical composition of a substance. Thus, chemical changes create new substances. Chemical changes involve the breaking of chemical bonds and the formation of new chemical bonds. Examples of chemical changes include fermentation, decomposition, oxidation, and combustion.

The total number of each type of atom within a chemical or physical change is the same before and after the change occurs. Thus, no matter is created nor destroyed during either a chemical or physical change. This concept is known as the law of conservation of matter.


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