مصادر الكيمياء موقع لتعليم الكيمياء بصورة مبسطة
Substances can undergo three type of changes:
– Physical changes
– Chemical changes (also known as chemical reactions)
– Nuclear changes (also known as nuclear reactions)
In a physical change the appearance (color, shape, etc.) of the substance may change, but the substance will remain the same substance. A phase change is an example of a physical change. For example, frozen water melting into liquid water is a physical change.
A chemical change is a “permanent change.” In this process, a substance (s) changes into a new substance(s). The new substance(s) possesses chemical and physical properties different from the original substance(s). For example, sodium metal and chlorine gas change into ordinary table salt (i.e., sodium chloride).
A nuclear change, which involves a change in the structure of the nucleus, is very dramatic. The energy per gram involved in nuclear changes is significantly greater than in chemical or physical changes.