Physical Science: Session 4

The wide range of properties (shape, phase etc) of the material will change, but the materials themselves are the same before and after the change. This change can be "undone".

The substance that existed at the beginning of the change did not end, it was the formation of a new substance. This change can not be "undone".

Particles of matter are broken down and atoms are rearranged into new particles to form new substances.

According to the above definitions, we can briefly explain the following state changes.

In many cases, the difference between physical change and chemical change is not clear. For example,

Dissolution of salt in water: As we know that salt can be recovered from water, this seems to be a physical change. However, looking at the microscopic level, you can see that the two atoms of salt, sodium and chlorine are separated from each other. In this case, we do not have new substances so salt in solution does not conform to the definition of microscopic chemical change, but there is no original form of matter - a mountain of alternating sodium and chlorine atoms. Does this mean semi-chemical and semi-physical change? It has a chemical change, but the scientists still classify the dissolution of salt as a physical change.

Production of Metal Alloy: When two metals are melted together, alloy metals with properties (eg thermal conductivity, electrical conductivity, density etc.) that are different from any of its components are produced. This may allow us to think that we have witnessed chemical changes. Indeed, new particles are not produced by melting two metals together. This indicates that they did not undergo a chemical reaction. For example, brass is about 60% copper and 40% zinc and is composed of separate copper and zinc atoms (ie there is no "minimum unit" yet brass). There is nothing like a brass molecule

Heating and cooling of specific rubbers and plastics: Exposing specific rubbers or plastics to heat or cold may cause chemical reactions (for example, the material becomes hard and brittle) because performance may change. Although chemical reactions occur, they bond only different parts of the polymer that makes up rubber and plastic. These new bonds increase the stiffness of the material, but the particles of the material do not change.

During physics research, many of our physics instructors use the subject physics as the source of all science. This is true for a long time before scientific fields such as biology and chemistry evolve, but most forms of scientific research are based on physical quantities and their interrelationships. Today, physics has evolved to include so much power, magnetism, power, and energy. Each part of this chapter is intensive and requires a lot of guidance to keep students under control. Physics is not just writing expressions on boards or on paper after the formula. Physical counselors need to develop a learning environment for students to explore scientific concepts in their daily lives. This teaching method will help our students to have a comprehensive understanding of physics, not just memorizing expressions.

Physics is fundamental physics. Until recently, physics and natural philosophy have been used in science alternately for the purpose of discovering and formulating the basic laws of nature. Physics began to show that part of physics is not included in astronomy, chemistry, geology, engineering, as the development of modern science and the development of specialization. However, physics plays an important role in all natural sciences and in all these fields, physical laws and measurements are of particular interest, such as astrophysics, geophysics, biophysics, There are fields such as psychophysics. Name Physics can be defined based on material science, exercise, energy. The law is usually expressed in an economic and accurate mathematical language.