![]() The kinetic molecular theory of heat states that the phenomenon of heat is identical to molecular motion. Most deformations are reversible a dent in a metal can be undone, but whether they actually can be undone is a practical matter that depends on the context. In the context of material sciences, the tendency for a material to permanently deform under mechanical stress is called creep. In fact, this is just what we mean when we call something hard it is resistant to having its molecular or atomic structure changed by a mechanical force. Some objects and arrangements are much more resistant to mechanical deformation than others. Credit: “Deformation” Emok via WikiCommons. Mechanical deformation is a physical change caused by the application of an external force. Crumpling a piece of paper, shattering a wine glass, or denting a metal plate with a hammer are all examples of mechanical deformations that arise from the application of some external force. Mechanical deformation involves a change in the spatial arrangement of atoms or molecules by the application of a mechanical force. Mechanical deformation is probably the simplest example of physical change. Most physical changes are reversible to some degree, though the reversibility of a change is not a condition for it being a physical change some chemical changes are reversible as well. An ice cube that has melted can be frozen again, so melting is a reversible process. Physical changes that can be undone are called reversible. Chemical changes involve an alteration of the chemical composition of the substance. Such a change is chemical, as it involves the breaking or forming of chemical bonds. Physics deals chiefly with continuous varying quantities, while chemistry deals chiefly with whole numbers.” - Max PlanckĬontrast this with a chemical change, like electrolysis, where one molecule of water is split into its atomic components, oxygen and hydrogen. “Physical changes take place continuously, while chemical changes take place discontinuously. ![]() The water becomes fluid and loses its definite shapes because its molecules are no longer fixed in a rigid spatial arrangement anymore. ![]() The change in the water’s properties is a consequence of the change in the arrangement of its molecules. The chemical composition of water molecules (H 2O) do not change they are still made out of 2 hydrogen atoms and 1 oxygen atom. When an ice cube melts, its constituent molecules change their arrangement and gain some properties, like flow, or lose some properties, like definite shape. Most of the time, a physical change is the result of the spatial rearrangement of atoms that make up the object.Ī simple example of a physical change is an ice cube melting. Most of the time, a physical change results in a change in the physical properties and behavior of an object, such as its shape, size, color volume, density, and texture. ![]() A physical change is opposed to a chemical change, which involves the breaking and formation of new chemical bonds. An object undergoes a physical change when there is some alteration of its physical structure or arrangements, but not its chemical composition. In chemistry, a physical change is a change to the form or structure of a chemical compound, but not to its chemical composition. ![]()
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