What physical phenomena exist. The changes that take place in bodies are called physical phenomena. How to distinguish between physical and chemical changes
Ticket number 1
1. What physics studies. Some physical terms. Observations and Experiments. Physical quantities. Measurement of physical quantities. Accuracy and error of measurements.
Physics is the science of the most general properties of bodies and phenomena.
How does a person know the world? How does he investigate natural phenomena, gaining scientific knowledge about him?
A person gets the very first knowledge from observations for nature.
To get the right knowledge, sometimes simple observation is not enough and you need to conduct experiment - specially prepared experiment .
Experiments are carried out by scientists a pre-planned plan with a specific purpose .
During experiments measurements are taken with the help of special devices for physical quantities. Examples physical quantities are: distance, volume, speed, temperature.
So, observations and experiments are the source of physical knowledge.
Physical laws are based and verified on empirically established facts. An equally important way of knowing is theoretical description of the phenomenon . Physical theories allow one to explain known phenomena and predict new ones that have not yet been discovered.
The changes that take place in bodies are called physical phenomena.
Physical phenomena are divided into several types.
Views physical phenomena:
1. Mechanical phenomena (for example, the movement of cars, airplanes, celestial bodies, fluid flow).
2. Electrical phenomena (for example, electricity, heating of conductors with current, electrification of bodies).
3. Magnetic phenomena (for example, the effect of magnets on iron, the effect magnetic field Earth on the compass needle).
4. Optical phenomena (for example, reflection of light from mirrors, emission of light rays from various light sources).
5. Thermal phenomena (melting of ice, boiling of water, thermal expansion of bodies).
6. Atomic phenomena (for example, the operation of atomic reactors, the decay of nuclei, the processes taking place inside the stars).
7. Sound phenomena (bell ringing, music, thunder, noise).
Physical terms Are special words used in physics for brevity, definiteness, and convenience.
Physical body Is every object around us. (Showing physical bodies: pen, book, desk)
Substance is all that the physical bodies are made of. (Showing physical bodies consisting of different substances)
Matter- this is everything that exists in the Universe regardless of our consciousness (celestial bodies, plants, animals, etc.)
Physical phenomena- these are changes taking place with physical bodies.
Physical quantities are measurable properties of bodies or phenomena.
Physical devices- these are special devices that are designed to measure physical quantities and conduct experiments.
Physical quantities:
height h, mass m, path s, speed v, time t, temperature t, volume V, etc.
Units of measurement of physical quantities:
International system of units SI:
(international system)
Basic:
Length - 1 m - (meter)
Time - 1 s - (second)
Weight - 1 kg - (kilogram)
Derivatives:
Volume - 1 m³ - (cubic meter)
Speed - 1 m / s - (meter per second)
In this expression:
number 10 - numerical value of time,
the letter "s" is an abbreviation for a unit of time (seconds),
and the combination of 10 s is the time value.
Unit names prefixes:
To make it more convenient to measure physical quantities, in addition to the basic units, multiple units are used, which are 10, 100, 1000, etc. more main
g - hecto (× 100) k - kilo (× 1000) M - mega (× 1000 000)
1 km (kilometer) 1 kg (kilogram)
1 km = 1000 m = 10³ m 1 kg = 1000 g = 10³ g
Since ancient times, people have been collecting information about the world in which they live. There was only one science that unites all the information about nature that mankind has accumulated at that time. Then people did not yet know that they were observing examples of physical phenomena. At present, this science is called "natural science".
What physical science studies
Over time, scientific ideas about the world around them have changed markedly - there are much more of them. Natural science has split into many separate sciences, including biology, chemistry, astronomy, geography, and others. Physics is not the last in a number of these sciences. Discoveries and achievements in this area have allowed humanity to possess new knowledge. These include the structure and behavior of various objects of all sizes (from giant stars to the smallest particles - atoms and molecules).
The physical body is ...
There is a special term "matter", which in the circles of scientists is called everything that is around us. A physical body consisting of matter is any substance that occupies a certain place in space. Any physical body in action can be called an example of a physical phenomenon. Based on this definition, we can say that any object is a physical body. Examples of physical bodies: button, notebook, chandelier, cornice, moon, boy, clouds.
What is a physical phenomenon
Any matter is in constant flux. Some bodies move, others touch the third, the fourth rotate. It is not for nothing that many years ago the philosopher Heraclitus uttered the phrase "Everything flows, everything changes." Scientists even have a special term for such changes - these are all phenomena.
Everything that moves belongs to physical phenomena.
What are the types of physical phenomena
- Thermal.
These are phenomena when, due to the influence of temperature, some bodies begin to transform (shape, size and state change). An example of physical phenomena: under the influence of the warm spring sun, icicles melt and turn into liquid, with the onset of cold weather, the puddles freeze, boiling water becomes vapor.
- Mechanical.
These phenomena characterize a change in the position of one body in relation to the rest. Examples: the clock is running, the ball is jumping, the tree is swinging, the pen is writing, the water is flowing. They are all in motion.
- Electrical.
The nature of these phenomena fully justifies its name. The word "electricity" has its roots in the Greek language, where "electron" means "amber". The example is quite simple and probably familiar to many. When you suddenly take off your woolen sweater, you can hear a slight crackling sound. If you do this by turning off the light in the room, then you can see sparks.
- Light.
The body participating in the phenomenon associated with light is called luminous. As an example of physical phenomena, we can cite the well-known star of our Solar system- The sun, as well as any other star, lamp, and even a firefly bug.
- Sound.
The propagation of sound, the behavior of sound waves in collisions with an obstacle, as well as other phenomena that are somehow related to sound, belong to this type of physical phenomenon.
- Optical.
They are due to light. So, for example, man and animals are able to see, because there is light. This group also includes the phenomena of propagation and refraction of light, its reflection from objects and passage through different media.
Now you know what physical phenomena are. However, it should be understood that there is a certain difference between natural and physical phenomena. Thus, in a natural phenomenon, several physical phenomena occur simultaneously. For example, when lightning strikes the ground, the following sound, electrical, heat and light occur.
We are surrounded by an endlessly diverse world of substances and phenomena.
It is constantly changing.
Any changes that occur to bodies are called phenomena. The birth of stars, the change of day and night, the melting of ice, the swelling of buds on trees, the flashing of lightning during a thunderstorm, and so on - all these are natural phenomena.
Physical phenomena
Let's remember that bodies are made of substances. Note that in some phenomena the substances of the bodies do not change, while in others they do. For example, if you tear a piece of paper in half, then, despite the changes that have occurred, the paper remains paper. If the paper is burned, it will turn into ash and smoke.
Phenomena in which the size, shape of bodies, the state of substances can change, but substances remain the same, do not turn into others, are called physical phenomena(evaporation of water, glow of a light bulb, sound of strings musical instrument etc.).
Physical phenomena are extremely varied. Among them there are mechanical, thermal, electrical, light and etc.
Let's remember how clouds float across the sky, an airplane flies, a car rides, an apple falls, a trolley rolls, etc. In all these phenomena, objects (bodies) move. The phenomena associated with a change in the position of a body in relation to other bodies are called mechanical(translated from Greek "mehane" means machine, tool).
Many phenomena are caused by changes in heat and cold. In this case, changes in the properties of the bodies themselves occur. They change shape, size, the state of these bodies changes. For example, when heated, ice turns into water, water - into steam; when the temperature drops, steam turns into water, water - into ice. The phenomena associated with the heating and cooling of bodies are called thermal(fig. 35).
Rice. 35. Physical phenomenon: the transition of a substance from one state to another. If you freeze water droplets, ice will reappear
Consider electrical phenomena. The word "electricity" comes from the Greek word for "electron" - amber. Recall that when you quickly take off your wool sweater, you hear a slight crackling sound. If you do the same in total darkness, you will also see sparks. This is the simplest electrical phenomenon.
To get acquainted with another electrical phenomenon, do the following experiment.
Pick up small pieces of paper and place them on the table top. Comb through clean, dry hair with a plastic comb and bring it up to the pieces of paper. What happened?
Rice. 36. Small pieces of paper are attracted to the comb
Bodies that, after rubbing, are capable of attracting light objects are called electrified(fig. 36). Lightning in thunderstorms, auroras, electrification of paper and synthetic fabrics are all electrical phenomena. The operation of a telephone, radio, television, and various household appliances are examples of human use of electrical phenomena.
The phenomena that are associated with light are called light. Light is emitted by the Sun, stars, lamps and some living things, such as firefly beetles. Such bodies are called luminous.
We see under the condition of exposure to light on the retina of the eye. We cannot see in absolute darkness. Objects that do not emit light themselves (for example, trees, grass, pages of this book, etc.) are visible only when they receive light from some luminous body and reflect it from their surface.
The moon, which we often speak of as a night light, is in reality only a kind of reflector of sunlight.
Studying the physical phenomena of nature, man learned to use them in everyday life, everyday life.
1. What are called natural phenomena?
2. Read the text. List what natural phenomena are called in it: “Spring has come. The sun is getting warmer. The snow is melting, streams are running. On the trees buds swelled, rooks flew in. "
3. What phenomena are called physical?
4. From the physical phenomena listed below, write down the mechanical phenomena in the first column; in the second - thermal; in the third - electric; in the fourth, light phenomena.
Physical phenomena: flash of lightning; snow melting; coast; melting of metals; work of an electric bell; rainbow in the sky; sunny bunny; moving stones, sand with water; boiling water.
| <<< Назад
|
Forward >>> |
Physical bodies are the "actors" of physical phenomena. Let's get acquainted with some of them.
Mechanical phenomena
Mechanical phenomena are the movement of bodies (Fig. 1.3) and their action on each other, for example, repulsion or attraction. The action of bodies on each other is called interaction.
We will get acquainted with mechanical phenomena in more detail this academic year.
Rice. 1.3. Examples of mechanical phenomena: movement and interaction of bodies during sports competitions (a, b, c); the movement of the Earth around the Sun and its rotation around its own axis (r)
Sound phenomena
Sound phenomena, as the name suggests, are phenomena associated with sound. These include, for example, the propagation of sound in air or water, as well as the reflection of sound from various obstacles, such as mountains or buildings. When sound is reflected, an echo familiar to many arises.
Thermal phenomena
Thermal phenomena are the heating and cooling of bodies, as well as, for example, evaporation (transformation of liquid into vapor) and melting (transformation solid into liquid).
Thermal phenomena are extremely widespread: for example, they cause the water cycle in nature (Fig. 1.4).
Rice. 1.4. The water cycle in nature
Heated sunbeams the water of the oceans and seas evaporates. As the steam rises, it cools down, turning into water droplets or ice crystals. They form clouds, from which water returns to Earth in the form of rain or snow.
The real "laboratory" of thermal phenomena is the kitchen: whether soup is boiled on the stove, water is boiling in a kettle, whether food is frozen in the refrigerator - all these are examples of thermal phenomena.
The operation of a car engine is also caused by thermal phenomena: when gasoline burns, a very hot gas is formed, which pushes the piston (engine part). And the movement of the piston is transmitted through special mechanisms to the wheels of the car.
Electrical and magnetic phenomena
The most striking (in the literal sense of the word) example of an electrical phenomenon is lightning (Fig. 1.5, a). Electric lighting and electric transport (Fig. 1.5, b) became possible due to the use of electrical phenomena. Examples of magnetic phenomena are the attraction of iron and steel objects by permanent magnets, and the interaction of permanent magnets.
Rice. 1.5. Electrical and magnetic phenomena and their uses
The compass needle (Fig. 1.5, c) turns so that its "north" end points to the north precisely because the arrow is a small permanent magnet, and the Earth is a huge magnet. The northern lights (Fig. 1.5, d) are caused by the fact that electrically charged particles flying from space interact with the Earth as with a magnet. Electrical and magnetic phenomena cause the operation of televisions and computers (Fig. 1.5, e, f).
Optical phenomena
Wherever we look, we will see optical phenomena everywhere (Fig. 1.6). These are phenomena associated with light.
An example of an optical phenomenon is the reflection of light by various objects. The rays of light reflected by objects fall into our eyes, due to which we see these objects.
Rice. 1.6. Examples of optical phenomena: The sun emits light (s); The moon reflects sunlight (b); mirrors reflect light especially well (c); one of the most beautiful optical phenomena - rainbow (g)
About the world around. Apart from the usual curiosity, this was due to practical needs. After all, for example, if you know how to raise
and move heavy stones, then you can build strong walls and build a house that is more comfortable to live in than in a cave or dugout. And if you learn to smelt metals from ores and make plows, scythes, axes, weapons, etc., you will be able to plow the field better and get a higher yield, and in case of danger you will be able to protect your land.
In ancient times, there was only one science - it combined all the knowledge about nature that mankind had accumulated by that time. Today this science is called natural science.
Learning about physical science
Light is another example of an electromagnetic field. You will get acquainted with some of the properties of light in the study of Section 3.
3. Remembering physical phenomena
The matter around us is constantly changing. Some bodies move relative to each other, some of them collide and, possibly, collapse, others are formed from some bodies ... The list of such changes can be continued and continued - it is not for nothing that in ancient times the philosopher Heraclitus remarked: "Everything flows, everything changes." Changes in the world around us, that is, in nature, scientists call a special term - phenomena.
Rice. 1.5. Examples of natural phenomena
Rice. 1.6. A complex natural phenomenon - a thunderstorm can be represented as a combination of a number of physical phenomena
Sunrise and sunset, avalanche, volcanic eruption, horse running, panther jump - all these are examples of natural phenomena (Fig. 1.5).
To better understand complex natural phenomena, scientists divide them into a set of physical phenomena - phenomena that can be described using physical laws.
In fig. 1.6 shows a set of physical phenomena that form a complex natural phenomenon - a thunderstorm. So, lightning - a huge electrical discharge - is an electromagnetic phenomenon. If lightning strikes a tree, it will flare up and begin to emit heat - physicists in this case speak of a thermal phenomenon. The rumble of thunder and the crackle of a burning tree are sound phenomena.
Examples of some physical phenomena are given in the table. Take a look at the first row of the table, for example. What can be in common between the flight of a rocket, the fall of a stone and the rotation of an entire planet? The answer is simple. All examples of phenomena given in this line are described by the same laws - the laws of mechanical motion. Using these laws, you can calculate the coordinates of any moving body (be it a stone, a rocket or a planet) at any moment of time that interests us.
Rice. 1.7 Examples of electromagnetic phenomena
Each of you, taking off your sweater or combing your hair with a plastic comb, probably paid attention to the tiny sparks that appear at the same time. Both these sparks and the mighty lightning discharge refer to the same electromagnetic phenomena and, accordingly, obey the same laws. Therefore, to study electromagnetic phenomena, one should not wait for a thunderstorm. It is enough to study how safe sparks behave in order to understand what to expect from lightning and how to avoid possible danger. For the first time such studies were carried out by the American scientist B. Franklin (1706-1790), who invented effective remedy lightning protection - lightning rod.
Having studied physical phenomena separately, scientists establish their relationship. Thus, a lightning discharge (electromagnetic phenomenon) is necessarily accompanied by a significant increase in temperature in the lightning channel (thermal phenomenon). The study of these phenomena in their interconnection allowed not only to better understand the natural phenomenon - a thunderstorm, but also to find a way of practical application of electromagnetic and thermal phenomena. Surely each of you, passing by the construction site, saw workers in protective masks and dazzling flashes of electric welding. Electric welding (a method of joining metal parts using an electric discharge) is an example of the practical use of scientific research.
4. Determine what physics studies
Now that you have learned what matter and physical phenomena are, it's time to determine what is the subject of physics study. This science studies: the structure and properties of matter; physical phenomena and their relationship.
- summing up
The world around us is made of matter. There are two types of matter: the substance of which all physical bodies are composed, and the field.
The world that surrounds us is constantly changing. These changes are called phenomena. Thermal, light, mechanical, sound, electromagnetic phenomena are all examples of physical phenomena.
The subject of physics study is the structure and properties of matter, physical phenomena and their relationship.
- Control questions
What does physics study? Give examples of physical phenomena. Can events that occur in a dream or in the imagination be considered physical phenomena? 4. What substances do the following bodies consist of: textbook, pencil, soccer ball, glass, car? What physical bodies can be made of glass, metal, wood, plastic?
Physics. Grade 7: Textbook / F. Ya. Bozhinova, N. M. Kiryukhin, E. A. Kiryukhina. - X .: Ranok Publishing House, 2007. - 192 p .: ill.
Lesson content lesson outline and support frame lesson presentation interactive technologies accelerative teaching methods Practice tests, online testing tasks and exercises homework workshops and trainings questions for class discussion Illustrations video and audio materials photos, pictures, graphics, tables, diagrams comics, parables, sayings, crosswords, anecdotes, jokes, quotes Supplements
Loading...