We are surrounded by endless diverse world 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
Recall that bodies are made up of substances. Note that in some phenomena the substances of bodies do not change, while in others they change. For example, if you tear a piece of paper in half, then, despite the changes that have occurred, the paper will remain paper. If the paper is burned, it will turn into ashes and smoke.
Phenomena in which the size, shape of bodies, the state of substances can change, but substances remain the same, do not change into others, are called physical phenomena(evaporation of water, the glow of an electric bulb, the sound of strings musical instrument etc.).
Physical phenomena are extremely diverse. Among them are distinguished mechanical, thermal, electrical, lighting and etc.
Let's remember how clouds float across the sky, an airplane flies, a car drives, an apple falls, a cart rolls, etc. In all of these phenomena, objects (bodies) move. Phenomena associated with a change in the position of a body in relation to other bodies are called mechanical(translated from the Greek "mehane" means machine, tool).
Many phenomena are caused by the change of heat and cold. In this case, the properties of the bodies themselves change. 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 matter from one state to another. If you freeze drops of water, ice will reappear
Consider electrical phenomena. The word "electricity" comes from Greek word"electron" amber. Remember that when you quickly take off your woolen sweater, you hear a slight crackle. If you do the same in complete darkness, you will also see sparks. This is the simplest electrical phenomenon.
To get acquainted with another electrical phenomenon, do the following experiment.
Tear off small pieces of paper and place them on the table surface. Comb clean and dry hair with a plastic comb and bring it to the pieces of paper. What happened?
Rice. 36. Small pieces of paper are attracted to the comb
Bodies that are capable of attracting light objects after rubbing are called electrified(Fig. 36). Lightning during thunderstorms, auroras, electrification of paper and synthetic fabrics - all these are electrical phenomena. Operation of telephone, radio, TV, various household appliances are examples of human use of electrical phenomena.
Phenomena that are associated with light are called light. Light comes from the sun, stars, lamps, and some living things, such as fireflies. Such bodies are called luminous.
We see when light hits the retina. We cannot see in absolute darkness. Objects that do not themselves emit light (for example, trees, grass, the 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 star, is in reality only a kind of reflector of sunlight.
By studying the physical phenomena of nature, man has learned to use them in Everyday life, 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 hotter. Snow melts, streams run. Buds swelled on the trees, rooks flew in.
3. What phenomena are called physical?
4. From the physical phenomena listed below, write in the first column mechanical phenomena; in the second - thermal; in the third - electrical; in the fourth - light phenomena.
Physical phenomena: lightning flash; snow melting; coast; melting of metals; operation of an electric bell; rainbow in the sky; sunbeam; moving stones, sand with water; boiling water.
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1. What does physics study. 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 the phenomena of nature, receiving scientific knowledge about him?
The very first knowledge a person receives from observations behind nature.
To get the right knowledge, sometimes simple observation is not enough and you need to conduct experiment - a specially prepared experiment .
Experiments are carried out by scientists premeditated plan with a specific purpose .
During the experiments measurements are taken using special instruments of physical quantities. Examples physical quantities are: distance, volume, speed, temperature.
So, the source of physical knowledge is observations and experiments.
Physical laws are based and tested on facts established by experience. An equally important way of knowing theoretical description of the phenomenon . Physical theories make it possible to explain known phenomena and predict new ones that have not yet been discovered.
Changes that occur with bodies are called physical phenomena.
Physical phenomena are divided into several types.
Types of physical phenomena:
1. Mechanical phenomena (for example, the movement of cars, aircraft, celestial bodies, fluid flow).
2. Electrical phenomena (for example, electricity, heating conductors with current, electrization 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, the reflection of light from mirrors, the emission of light rays from various sources Sveta).
5. Thermal phenomena (melting ice, boiling water, thermal expansion bodies).
6. Atomic phenomena (for example, the operation of nuclear reactors, the decay of nuclei, processes occurring inside 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 that surrounds us. (Showing physical bodies: pen, book, school desk)
Substance It is everything that 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 are changes that occur to physical bodies.
Physical quantities are the measurable properties of bodies or phenomena.
Physical Instruments- 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)
Main:
Length - 1 m - (meter)
Time - 1 s - (second)
Weight - 1 kg - (kilogram)
Derivatives:
Volume - 1 m³ - (cubic meter)
Velocity - 1 m/s - (meter per second)
In this expression:
the number 10 is the numerical value of the time,
the letter "s" is an abbreviation for the unit of time (seconds),
and the combination of 10 s is the time value.
Prefixes to unit names:
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 basic
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
A phenomenon is any manifestation of something, as well as any change in the world around us. The meaning of this word is determined by the context, namely the adjective next to the term "phenomenon". It is difficult to understand what a phenomenon is without examples, so we will give them.
- A physical phenomenon is a change state of aggregation substances.
- In this area, there are such unusual natural phenomena as petrified waves.
- He was frightened by something that could be called a paranormal phenomenon.
Let us consider in more detail the term "Phenomenon" depending on the context.
What is a physical phenomenon
First of all, note that a physical phenomenon is a process, not the result of something. This is the process of ongoing changes in the state or position of physical systems. Remember that a physical phenomenon is one in which there is no transformation of one substance into another. Its composition will remain the same, but the state or position will change.
Physical phenomena are classified as follows:
- electrical phenomena. They involve electric charges. For example, lightning, electric current.
- mechanical phenomena. The movement will be relative to each other. For example, the movement of cars on the road.
- Thermal phenomena. They are associated with changes in body temperature. For example, melting snow.
- Optical phenomena. They are connected with the metamorphoses of the rays of light. For example, a rainbow.
- magnetic phenomena. Occurs when magnetic properties on one subject or another. For example, a compass with an arrow pointing north.
- Atomic Phenomena. Occur during metamorphoses in the internal structure of matter. For example, the glow of the stars.
What are natural phenomena
Natural phenomena are considered climatic and meteorological manifestations of nature that occur naturally. Rain, snow, storm, earthquake are all examples of natural phenomena.
It is important to understand what a natural phenomenon is and how it is interconnected with physical phenomena. So, in one natural phenomenon, several physical phenomena can be counted. That is, the concept of "natural phenomenon" is broader. For example, such a natural phenomenon as a thunderstorm includes the following physical phenomena: the movement of clouds and rain (mechanical phenomena), lightning (electrical phenomenon), burning a tree from a lightning strike (thermal phenomenon).
What is paranormal activity
When they talk about a paranormal phenomenon, they mean any changes in the surrounding reality that are not the norm, an ordinary phenomenon. They have no scientific explanation, no evidence. Their existence goes beyond understanding the usual picture of the world. Examples of paranormal phenomena are: crying icons, the biofield of living beings.
Dynamic change is built into nature itself. Everything changes in one way or another every moment. If you look closely, you will find hundreds of examples of physical and chemical phenomena that are quite natural transformations.
Change is the only constant in the universe
Ironically, change is the only constant in our universe. In order to understand physical and chemical phenomena (examples in nature are found at every turn), it is customary to classify them into types, depending on the nature of the end result caused by them. There are physical, chemical and mixed changes, which contain both the first and the second.
Physical and chemical phenomena: examples and meaning
What is a physical phenomenon? Any change that occurs in a substance without changing it chemical composition, are physical. They are characterized by changes in physical attributes and financial condition(solid, liquid or gaseous), density, temperature, volume that occur without changing its fundamental chemical structure. There is no creation of new chemical products or changes in the total mass. In addition, this type of change is usually temporary and in some cases completely reversible.
When you mix chemicals in the lab, you can easily see the reaction, but there are many chemical reactions going on in the world around you every day. A chemical reaction changes molecules, while a physical change only rearranges them. For example, if we take chlorine gas and metallic sodium and combine them, we get table salt. The resulting substance is very different from any of its constituent parts. This is a chemical reaction. If we then dissolve this salt in water, we simply mix the salt molecules with the water molecules. There is no change in these particles, it is a physical transformation.
Examples of physical changes
Everything is made up of atoms. When atoms combine, different molecules are formed. The different properties that objects inherit are the result of different molecular or atomic structures. The main properties of an object depend on their molecular arrangement. Physical changes occur without changing the molecular or atomic structure of objects. They simply transform the state of an object without changing its nature. Melting, condensation, volume change and evaporation are examples of physical phenomena.
Additional examples of physical changes: metal expanding when heated, sound transmission through air, water freezing into ice in winter, copper being drawn into wires, clay forming on various objects, ice cream melting to a liquid, heating metal and changing it into another form, sublimation of iodine when heating, the fall of any object under the influence of gravity, the ink is absorbed by chalk, the magnetization of iron nails, a snowman melting in the sun, glowing incandescent lamps, magnetic levitation of an object.
How to distinguish between physical and chemical changes?
Many examples of chemical and physical phenomena can be found in life. It is often difficult to tell the difference between the two, especially when both can occur at the same time. To define physical changes, set next questions:
- Is the state of an object's state a change (gaseous, solid, and liquid)?
- Is the change a purely limited physical parameter or characteristic such as density, shape, temperature, or volume?
- Is the chemical nature of an object a change?
- Are there chemical reactions that lead to the creation of new products?
If the answer to one of the first two questions is yes, and there are no answers to the subsequent questions, it is most likely a physical phenomenon. Conversely, if the answer to any of the last two questions is yes, while the first two are no, then it is definitely a chemical phenomenon. The trick is just to clearly observe and analyze what you see.
Examples of chemical reactions in everyday life
Chemistry takes place in the world around you, not just in the laboratory. Matter interacts to form new products through a process called chemical reaction or chemical change. Every time you cook or clean, it's chemistry in action. Your body lives and grows through chemical reactions. There are reactions when you take medicine, light a match and sigh. Here are 10 chemical reactions in everyday life. This is just a small selection of those examples of physical and chemical phenomena in life that you see and experience many times every day:
- Photosynthesis. Chlorophyll in plant leaves converts carbon dioxide and water into glucose and oxygen. It is one of the most common daily chemical reactions and also one of the most important because it is how plants produce food for themselves and animals and convert carbon dioxide into oxygen.
- Aerobic cellular respiration is a reaction with oxygen in human cells. Aerobic cellular respiration is the opposite process of photosynthesis. The difference is that energy molecules combine with the oxygen we breathe to release the energy our cells need, as well as carbon dioxide and water. The energy used by cells is chemical energy in the form of ATP.
- Anaerobic respiration. Anaerobic respiration produces wine and other fermented foods. Your muscle cells perform anaerobic respiration when you run out of oxygen, such as during intense or prolonged exercise. Anaerobic respiration by yeast and bacteria is used for fermentation to produce ethanol, carbon dioxide and other chemical substances that produce cheese, wine, beer, yogurt, bread and many other common foods.
- Combustion is a type of chemical reaction. This is a chemical reaction in everyday life. Every time you light a match or a candle, light a fire, you see a combustion reaction. Incineration combines energy molecules with oxygen to produce carbon dioxide and water.
- Rust is a common chemical reaction. Over time, the iron develops a red, flaky coating called rust. This is an example of an oxidation reaction. Other everyday examples include the formation of verdigris on copper and the tarnishing of silver.
- Mixing chemicals causes chemical reactions. Baking powder and baking soda perform similar functions in baking, but they react differently to other ingredients, so you can't always swap them out. If you combine vinegar and baking soda for a chemical "volcano" or milk with baking powder in a recipe, you are experiencing a double bias or metathesis reaction (plus a few others). The ingredients are recombined to produce carbon dioxide gas and water. Carbon dioxide forms bubbles and helps "growing" bakery products. These reactions appear simple in practice, but often involve multiple steps.
- Batteries are examples of electrochemistry. Batteries use electrochemical or redox reactions to convert chemical energy into electrical energy.
- Digestion. Thousands of chemical reactions take place during digestion. As soon as you put food in your mouth, an enzyme in your saliva called amylase begins to break down sugars and other carbohydrates into more simple shapes that your body can absorb. The hydrochloric acid in your stomach reacts with food to break it down, and enzymes break down proteins and fats so they can be absorbed into the bloodstream through the intestinal wall.
- Acid-base reactions. Whenever you mix an acid (such as vinegar, lemon juice, sulfuric acid, hydrochloric acid) with an alkali (e.g. baking soda, soap, ammonia, acetone), you perform an acid-base reaction. These processes neutralize each other, producing salt and water. Sodium chloride is not the only salt that can be formed. For example, here is the chemical equation for an acid-base reaction that produces potassium chloride, a common substitute for table salt: HCl + KOH → KCl + H 2 O.
- Soap and detergents. They are purified by chemical reactions. Soap emulsifies dirt, which means that oily stains bind to the soap so that they can be removed with water. Detergents reduce the surface tension of water, so they can interact with oils, isolate them and wash them away.
- Chemical reactions in food preparation. Cooking is one big hands-on chemistry experiment. Cooking uses heat to bring about chemical changes in food. For example, when you boil an egg strongly, the hydrogen sulfide produced by heating egg white, can react with iron from egg yolk, forming a grey-green ring around the yolk. When you cook meat or baked goods, the Maillard reaction between amino acids and sugars gives Brown color and desired taste.
Other examples of chemical and physical phenomena
Physical Properties describe characteristics that do not change the substance. For example, you can change the color of paper, but it's still paper. You can boil water, but when you collect and condense the steam, it's still water. You can determine the mass of a sheet of paper and it's still paper.
Chemical properties are those that indicate how a substance reacts or does not react with other substances. When sodium metal is placed in water, it reacts violently to form sodium hydroxide and hydrogen. Sufficient heat is generated by the hydrogen escaping into the flame by reacting with the oxygen in the air. On the other hand, when you put a piece of copper metal into water, there is no reaction. So the chemical property of sodium is that it reacts with water, but the chemical property of copper is that it does not.
What other examples of chemical and physical phenomena can be given? Chemical reactions always occur between electrons in the valence shells of the atoms of elements in periodic table. Physical phenomena at low energy levels simply include mechanical interactions - random collisions of atoms without chemical reactions, such as atoms or gas molecules. When the collision energies are very high, the integrity of the nucleus of atoms is broken, leading to division or fusion of the species involved. Spontaneous radioactive decay usually considered a physical phenomenon.
Man lives in the natural world. You yourself and everything that surrounds you - air, trees, river, sun - these are different objects of nature. Objects of nature are constantly undergoing changes, which are called natural phenomena.
Since ancient times, people have been trying to understand: how and why do various phenomena occur? How do birds fly and why don't they fall? How can a tree float on water and why does it not sink? Some natural phenomena - thunder and lightning, solar and lunar eclipse- scared people until scientists figured out how and why they arise.
Observing and studying the phenomena occurring in nature, people have found their application in their lives. Watching the flight of birds (Fig. 1), people constructed an airplane (Fig. 2).
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Watching a floating tree, man learned to build ships, conquered the seas and oceans. Having studied the way the jellyfish move (Fig. 3), scientists came up with rocket engine(Fig. 4). By observing lightning, scientists discovered electricity, without which today people cannot live and work. All kinds of household electrical devices(lighting lamps, televisions, vacuum cleaners) surround us everywhere. Various electrical tools (electric drill, power saw, sewing machine) are used in school workshops and in production.
Scientists divided all physical phenomena into groups (Fig. 6):
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mechanical phenomena- these are phenomena that occur with physical bodies when they move relative to each other (the revolution of the Earth around the Sun, the movement of cars, the swing of a pendulum).
electrical phenomena- these are phenomena that arise during the appearance, existence, movement and interaction electric charges(electric current, lightning).
Magnetic phenomena- these are phenomena associated with the occurrence of magnetic properties in physical bodies (attraction of iron objects by a magnet, turning the compass needle to the north).
optical phenomena- these are phenomena that occur during the propagation, refraction and reflection of light (reflection of light from a mirror, mirages, the appearance of a shadow).
thermal phenomena- these are phenomena associated with the heating and cooling of physical bodies (boiling a kettle, the formation of fog, the transformation of water into ice).
Atomic Phenomena are phenomena that occur when internal structure substances of physical bodies (glow of the Sun and stars, atomic explosion).
Watch and explain. 1. Give an example of a natural phenomenon. 2. What group of physical phenomena does it belong to? Why? 3. Name the physical bodies that participated in physical phenomena.