Traveling to the country of “physics” - some basic understanding of matter (3)

All things in nature, or the particles that make up it, are inherently material and mobile. Microscopic particles have an "uncertainty principle". They are always moving, and you cannot determine where they will appear next. Newton said: "Matter is energy, and energy is matter." The mutual transformation between them is a kind of movement.

Matter and motion often express their existence in the form of shape and form of motion; but how we grasp it depends on magnitude. Quantity (physical quantity) often reflects the most essential things in matter and motion.

Therefore, when we grasp physics, we often understand them from the form (properties), movement (laws) of matter and the magnitude of their respective states (physical quantities). First, let’s talk about physical quantities, and then use physical quantities to understand form and motion.

Scientist Kelvin said:

In physics, the most essential quantities in reacting matter and motion are collectively called physical quantities.

All physical quantities have names, and the names of physical quantities are what we usually call physical concepts. For example, temperature, density, air pressure, etc. The units of physical quantities are often named after scientists, such as the unit of temperature Fahrenheit (Fahrenheit (1686-1736)), Celsius (Celsius (1701-1744)).

The science of physics can also be said in a sense that it is a science in which scientists are looking for physical quantities and discovering the relationships between physical quantities.

Scientists usually divide the space occupied by matter into four categories.

The first is macroscopic, which refers to the scale of objects visible to the naked eye.

The second is microscopic, which refers to the molecular and atomic scale that is invisible to the human eye.

The third is mesoscopic, which refers to the scale between molecules, atomic scales and the smallest particles visible to the naked eye.

For example, nanometer (10-9m) particles belong to the mesoscopic scale range. Microscopic particles at this scale usually have many peculiar properties. For example, nanoceramics, nanosteel tubes, nanomagnetic materials, nanocomposites (which can absorb electromagnetic waves and can be used as coatings for stealth aircraft), etc., all have various unique properties. This is also a manifestation of the change from quantitative change to qualitative change in the process of movement and change of matter.

The fourth is cosmic, which refers to the scale of celestial bodies that are very far away from us.

(Arranged from large to small: cosmic, macroscopic, mesoscopic, microscopic)

The forms of matter are solid, liquid, and gaseous, and they will transform into each other under certain conditions. If a substance changes directly from a solid state to a gaseous state, it is called sublimation. For example, if soap emits a smell, it means that the solid surface has sublimated. On the contrary, it is called sublimation. For example, the ice flowers, frost, rime, etc. on the windows in winter are all sublimation.

In essence, the morphological changes of matter are the result of the constant and irregular movement of a large number of invisible molecules inside the matter, as well as the interaction between molecules.

Normally, when a substance absorbs heat, the movement of its internal molecules will become more intense. As a result, some molecules that move at a higher speed will break away from the gravitational pull of the molecules inside the solid substance and leave the solid substance. directly into a gaseous state. When the formed gaseous material releases heat, the movement of the molecules inside it will slow down again, so they will condense together under the action of molecular gravity and return to the solid state.

This is the essential reason for the phenomenon of sublimation and sublimation of matter.

The properties of matter are also physical properties. In physics, we often see the terms "physical phenomena" and "physical changes", which refer to various phenomena, changes and properties that appear when the substance itself does not undergo qualitative changes. That is, physical phenomena, physical changes, and physical properties.

The physical properties of matter include: state, hardness, density, transparency, electrical conductivity, thermal conductivity, magnetism (the properties of objects that can attract iron, cobalt, nickel and other substances), elasticity and properties (normality) It means that the force is withdrawn and elastic deformation no longer occurs; as opposed to elasticity);

In addition, there are: brittleness, compression resistance, tensile strength, ductility, viscosity, color, toughness, corrosion resistance, Breathability, water absorption, etc. (As long as we can think of it, it is basically the same; so matter and matter are inextricably connected, and they all had the same root system a few years ago).

Different substances have different physical properties, and their properties determine their uses. For countless objects, it is a relatively simple method to study problems if they are classified and studied according to their physical properties. Scientists and inventors often use this method and have achieved fruitful results.

The magnitude of matter includes length, time, temperature, mass, density,..., each attribute has its magnitude, and they all originate from nature. For example, mass:

People define the mass of 1,000 cubic centimeters of pure water at 4°C as 1 kilogram (kg).

This is a single unit. In physics, there is also a composite unit. For example, people often use ratio and product methods to derive new physical quantities.

Since ratios and products usually involve two physical quantities, each of which has its own unit, the unit of the new physical quantity is a combination of the units of these two related physical quantities, which is usually called a composite unit. Physical phenomena or physical facts can be accurately described using ratio and product methods (mathematics is the best tool to carve out the details of nature).

Physics is a science that draws a general rule through experiments or phenomena, induction, generalization and summary, and then continuously verifies it. Of course, this is also a human ability. The methods of summary include outline format, table format and box diagram format.

Scientists commonly use three methods: text, charts (images, tables) and formulas (descriptions) to present their scientific research results; physics textbooks are basically written in this way.

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