Physical phenomena. Examples of physical phenomena and their descriptions

Dynamic change is built into nature itself. Everything changes one way or another every moment. If you look carefully, you will find hundreds of examples of physical and chemical phenomena that are completely natural transformations.

Change is the only constant in the Universe

Oddly enough, change is the only constant in our Universe. To understand physical and chemical phenomena (examples in nature are found at every step), it is customary to classify them into types, depending on the nature of the final 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 material state (solid, liquid or gaseous), density, temperature, volume, which occur without changing its fundamental chemical structure. There is no creation of new chemical products or changes in the total mass. Additionally, this type of change is usually temporary and in some cases completely reversible.

When you mix chemicals in a laboratory, it is easy to see the reaction, but there are many chemical reactions happening 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 sodium metal and combine them, we get table salt. The resulting substance is very different from any of its components. This is a chemical reaction. If we then dissolve this salt in water, we are simply mixing salt molecules with water molecules. There is no change in these particles, it is a physical transformation.

Examples of physical changes

Everything is made of atoms. When atoms combine, different molecules are formed. The different properties that objects inherit are a consequence of different molecular or atomic structures. The basic 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 physical phenomena.

Additional examples of physical changes: metal expanding when heated, sound transmitted through air, water freezing into ice in winter, copper being drawn into wires, clay forming on different objects, ice cream melting to a liquid, heating a metal and transforming it into another form, sublimation of iodine when heated, falling of any object by gravity, ink being absorbed by chalk, magnetization of iron nails, a snowman melting in the sun, glowing incandescent lamps, magnetic levitation of an object.

How do you differentiate 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 determine physical changes, ask the following questions:

• Is the state of an object's state a change (gaseous, solid, and liquid)?
• Is the change purely limited to a physical parameter or characteristic such as density, shape, temperature or volume?
• Does it chemical nature object change?
• Do chemical reactions occur that lead to the creation of new products?

If the answer to one of the first two questions is yes, and the answers to subsequent questions are no, it is most likely a physical phenomenon. And vice versa, if the answer to any of the two latest questions positive, while the first two are negative, this is definitely a chemical phenomenon. The trick is to simply observe clearly and analyze what you see.

Examples of chemical reactions in everyday life

Chemistry happens in the world around you, not just in the laboratory. Matter interacts to form new products through a process called a 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 sampling of the physical and chemical phenomena in life that you see and experience many times every day:

1. 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 make food for themselves and animals and convert carbon dioxide into oxygen.
2. 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.
3. Anaerobic respiration. Anaerobic respiration produces wine and other fermented foods. Your muscle cells perform anaerobic respiration when you deplete the oxygen supply, such as during intense or prolonged exercise. Anaerobic respiration by yeasts and bacteria is used for fermentation to produce ethanol, carbon dioxide and other chemicals that produce cheese, wine, beer, yogurt, bread and many other common foods.
4. Combustion is a type of chemical reaction. This is a chemical reaction in everyday life. Every time you light a match or a candle, or start a fire, you see a combustion reaction. Combustion combines energy molecules with oxygen to produce carbon dioxide and water.
5. Rust is a common chemical reaction. Over time, 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 tarnishing of silver.
6. 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 substitute another. If you combine vinegar and baking soda for a chemical "volcano" or milk and baking powder in a recipe, you are experiencing a double displacement or metathesis reaction (plus a few others). The ingredients are recombined to produce carbon dioxide gas and water. Carbon dioxide creates bubbles and helps the baked goods "grow". These reactions appear simple in practice, but often involve several steps.
7. Batteries are examples of electrochemistry. Batteries use electrochemical or redox reactions to convert chemical energy into electrical energy.
8. Digestion. Thousands of chemical reactions occur 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, which 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 blood through the intestinal wall.
9. Acid-base reactions. Whenever you mix an acid (such as vinegar, lemon juice, sulfuric acid, hydrochloric acid) with alkali (for example, 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 the acid-base reaction that produces potassium chloride, a common table salt substitute: HCl + KOH → KCl + H2O.
10. Soap and detergents. They are purified through chemical reactions. Soap emulsifies dirt, which means oil stains bind to the soap so they can be removed with water. Detergents reduce the surface tension of water so they can interact with oils, sequestering them and washing them away.
11. Chemical reactions during cooking. Cooking is one big hands-on chemistry experiment. Cooking uses heat to cause chemical changes in food. For example, when you boil an egg hard, hydrogen sulfide produced by heating the egg white can react with the iron from the egg yolk, forming a gray-green ring around the yolk. When you cook meat or baked goods, the Maillard reaction between amino acids and sugars produces Brown color and desired taste.

Other examples of chemical and physical phenomena

Physical properties describe characteristics that do not change a substance. For example, you can change the color of the paper, but it's still paper. You can boil water, but when you collect and condense the steam, it is still water. You can determine the mass of a piece of paper, and it is still paper.

Chemical properties are those that show 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. Enough heat is generated as the hydrogen escapes into the flame, reacting with the oxygen in the air. On the other hand, when you put a piece of copper metal in water, no reaction occurs. Thus, chemical property 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 atoms of elements in the periodic table. Physical phenomena at low energy levels simply involve mechanical interactions - random collisions of atoms without chemical reactions, such as atoms or gas molecules. When collision energies are very high, the integrity of the nucleus of atoms is disrupted, leading to fission or fusion of the species involved. Spontaneous radioactive decay is generally considered a physical phenomenon.

Since ancient times, people have been collecting information about the world in which they live. There was only one science that united all the information about nature that humanity had accumulated at that time. At that time, people did not yet know that they were observing examples of physical phenomena. Currently, this science is called “natural science”.

What does physical science study?

Over time, scientific ideas about the world around us have changed noticeably - there are many more of them. Natural science split into many separate sciences, including: biology, chemistry, astronomy, geography and others. In a number of these sciences there is no last place takes up physics. Discoveries and achievements in this field have allowed humanity to acquire 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 scientific circles is used to describe 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, notepad, chandelier, cornice, Moon, boy, clouds.

What is a physical phenomenon

Any matter is in constant change. Some bodies move, others come into contact with others, and others 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.

Physical phenomena include everything that moves.

What types of physical phenomena are there?

• Thermal.

These are phenomena when, due to the effects of temperature, some bodies begin to transform (shape, size and condition 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, puddles freeze, boiling water becomes steam.

• Mechanical.

These phenomena characterize a change in the position of one body in relation to the others. Examples: a clock is running, a ball is jumping, a tree is shaking, a pen is writing, water is flowing. They are all in motion.

• Electrical.

The nature of these phenomena fully justifies their name. The word "electricity" has its roots in Greek language, where "electron" means "amber". The example is quite simple and probably familiar to many. When you suddenly take off a woolen sweater, you hear a small crack. If you do this by turning off the light in the room, you can see sparkles.

• Light.

A body participating in a phenomenon associated with light is called luminous. As an example of physical phenomena, we can give everyone famous star our solar system- The sun, as well as any other star, lamp, and even a firefly.

• Sound.

Sound propagation, behavior sound waves in collisions with an obstacle, as well as other phenomena that are in one way or another related to sound, belong to this type of physical phenomena.

• Optical.

They happen thanks to light. For example, humans 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 is worth understanding that there is a certain difference between natural and physical phenomena. Yes, when natural phenomenon Several physical phenomena occur simultaneously. For example, when lightning strikes the ground, the following phenomena occur: magnetic, sound, electrical, thermal and light.

>> Physical and chemical phenomena (chemical reactions). Let's experiment at home. External effects in chemical reactions

Physical and chemical phenomena (chemical reactions)

The material in this paragraph will help you figure out:

>what is the difference between physical and chemical phenomena.(chemical reactions);
> what external effects accompany chemical reactions.

In natural history lessons, you learned that various physical and chemical phenomena occur in nature.

Physical phenomena.

Each of you has repeatedly observed how ice melts, water boils or freezes. Ice, water and water vapor consist of the same molecules, so they are one substance (in different states of aggregation).

Phenomena in which a substance does not transform into another are called physical.

Physical phenomena include not only changes in substances, but also the glow of hot bodies, the passage electric current in metals, the spread of the smell of substances in the air, the dissolution of fat in gasoline, the attraction of iron to a magnet. Such phenomena are studied by the science of physics.

Chemical phenomena (chemical reactions).

One of the chemical phenomena is combustion. Let's consider the process of burning alcohol (Fig. 46). It occurs with the participation of oxygen contained in the air. When burned, alcohol seemingly turns into a gaseous state, just as water turns into steam when heated. But that's not true. If the gas obtained as a result of the combustion of alcohol is cooled, then part of it will condense into liquid, but not into alcohol, but into water. The rest of the gas will remain. With the help of additional experiment it can be proven that this residue is carbon dioxide.

Rice. 46. ​​Burning alcohol

So the alcohol that burns and oxygen, which participates in the combustion process, are converted into water and carbon dioxide.

Phenomena in which some substances are transformed into others are called chemical phenomena or chemical reactions.

Substances that enter into a chemical reaction are called starting substances, or reagents, and those that are formed are called final substances, or reaction products.

The essence of the chemical reaction considered is conveyed by the following entry:

alcohol + oxygen -> water + carbon dioxide
starting materials final substances
(reagents) (reaction products)

The reactants and products of this reaction are made up of molecules. During combustion, a high temperature is created. Under these conditions, the molecules of the reagents break down into atoms, which, when combined, form molecules of new substances - products. Therefore, all atoms are conserved during the reaction.

If the reactants are two ionic substances, then they exchange their ions. Other variants of interaction of substances are also known.

External effects accompanying chemical reactions.

By observing chemical reactions, the following effects can be recorded:

Change in color (Fig. 47, a);
gas release (Fig. 47, b);
formation or disappearance of sediment (Fig. 47, c);
appearance, disappearance or change in odor;
release or absorption of heat;
the appearance of a flame (Fig. 46), sometimes a glow.

Rice. 47. Some external effects during chemical reactions: a - appearance
coloring; b - gas release; c - appearance of sediment

Laboratory experiment No. 3

The appearance of color as a result of the reaction

Are solutions of soda ash and phenolphthalein colored?

Add 2 drops of phenolphthalein solution to a portion of soda solution I-2. What color appeared?

Laboratory experiment No. 4

Release of gas as a result of the reaction

Add a little chloride acid to the soda ash solution. What are you observing?

Laboratory experiment No. 5

The appearance of a precipitate as a result of the reaction

Add 1 ml of copper sulfate solution to the soda ash solution. What's happening?

The appearance of a flame is a sign of a chemical reaction, that is, it indicates a chemical phenomenon. Other external effects can also be observed during physical phenomena. Let's give a few examples.

Example 1. Silver powder obtained in a test tube as a result of a chemical reaction has grey colour. If you melt it and then cool the melt, you will get a piece of metal, but not gray, but white, with a characteristic shine.

Example 2. If you heat natural water, gas bubbles will begin to emerge from it long before boiling. This is dissolved air; its solubility in water decreases when heated.

Example 3. The unpleasant odor in the refrigerator disappears if granules of silica gel, one of the silicon compounds, are placed in it. Silica gel absorbs molecules of various substances without destroying them. Activated carbon works in a similar way in a gas mask.

Example 4 . When water turns into steam, heat is absorbed, and when water freezes, heat is released.

To determine what kind of transformation has occurred - physical or chemical, you should carefully observe it, as well as comprehensively examine the substances before and after the experiment.

Chemical reactions in nature, everyday life and their significance.

Chemical reactions occur constantly in nature. Substances dissolved in rivers, seas, and oceans interact with each other, some react with oxygen. Plants absorb carbon dioxide from the atmosphere, water and dissolved substances from the soil and process them into proteins, fats, glucose, starch, vitamins, other compounds, as well as oxygen.

This is interesting

As a result of photosynthesis, about 300 billion tons of carbon dioxide are absorbed from the atmosphere each year, 200 billion tons of oxygen are released, and 150 billion tons of organic substances are formed.

Reactions involving oxygen, which enters living organisms during respiration, are very important.

Many chemical reactions accompany us in everyday life. They occur during frying meat, vegetables, baking bread, souring milk, fermenting grape juice, bleaching fabrics, burning various types fuel, hardening of cement and alabaster, blackening over time silver jewelry and so on.

Chemical reactions form the basis of such technological processes as the extraction of metals from ores, the production of fertilizers, plastics, synthetic fibers, medicines, and other important substances. By burning fuel, people provide themselves with heat and electricity. Using chemical reactions, they neutralize toxic substances and process industrial and household waste.

The occurrence of some reactions leads to negative consequences. Rusting of iron shortens the life of various mechanisms, equipment, Vehicle, leads to large losses of this metal. Fires destroy housing, industrial and cultural sites, historical values. Most foods spoil due to their interaction with oxygen in the air; in this case, substances are formed that have an unpleasant odor, taste and are harmful to humans.

conclusions

Physical phenomena are the phenomena in which each substance is conserved.

Chemical phenomena, or chemical reactions, are the transformation of one substance into another. They can be accompanied by various external effects.

Many chemical reactions take place in environment, in plants, animal and human organisms, accompany us in everyday life.

?
100. Match:

1) dynamite explosion; a) physical phenomenon;
2) solidification of molten paraffin; b) chemical phenomenon.
3) food burning in a frying pan;
4) the formation of salt during the evaporation of sea water;
5) separation of a strongly shaken mixture of water and vegetable oil;
6) fading of dyed fabric in the sun;
7) passage of electric current in the metal;

101. What external effects are accompanied by such chemical transformations: a) burning of a match; b) rust formation; c) fermentation of grape juice.

102. Why do you think alone food products(sugar, starch, vinegar, salt) can be stored indefinitely, while others (cheese, butter, milk) spoil quickly?

Experimenting at home

External effects in chemical reactions

1. Prepare small quantities of aqueous solutions citric acid and drinking soda. Pour portions of both solutions together into a separate glass. What's happening?

Add a few soda crystals to the remainder of the citric acid solution, and a few citric acid crystals to the remainder of the soda solution. What effects do you observe - the same or different?

2. Pour some water into three small glasses and add 1-2 drops of brilliant green alcohol solution, known as “zelenka,” to each. Add a few drops of ammonia to the first glass, and citric acid solution to the second. Has the color of the dye (green) in these glasses changed? If so, how exactly?

Write down the results of the experiments in a notebook and draw conclusions.

Popel P. P., Kryklya L. S., Chemistry: Pidruch. for 7th grade zagalnosvit. navch. closing - K.: VC "Academy", 2008. - 136 p.: ill.

Physical bodies are " actors» physical phenomena. Let's get to know 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 to know 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); 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 involving sound. These include, for example, the propagation of sound in air or water, as well as the reflection of sound from various obstacles - say, mountains or buildings. When sound is reflected, a familiar echo appears.

Thermal phenomena

Thermal phenomena are the heating and cooling of bodies, as well as, for example, evaporation (the transformation of liquid into vapor) and melting (the transformation solid into liquid).

Thermal phenomena are extremely widespread: for example, they determine the water cycle in nature (Fig. 1.4).

Rice. 1.4. Water cycle in nature

The water of the oceans and seas, heated by the sun's rays, evaporates. As the steam rises, it cools, 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 being cooked on the stove, whether 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 determined by thermal phenomena: when gasoline burns, a very hot gas is formed, which pushes the piston (motor 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 thanks to the use of electrical phenomena. Examples of magnetic phenomena are the attraction of iron and steel objects by permanent magnets, as well as 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 “northern” end points to the north precisely because the needle is small permanent magnet, and the Earth is a huge magnet. Northern lights(Fig. 1.5, d) is caused by the fact that electrically charged particles flying from space interact with the Earth as with a magnet. Electrical and magnetic phenomena determine 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. Rays of light reflected by objects enter our eyes, thanks to which we see these objects.

Rice. 1.6. Examples of optical phenomena: The sun emits light (a); Moon reflects sunlight(b); Mirrors (c) reflect light especially well; one of the most beautiful optical phenomena - rainbow (d)