Physical phenomena in chemistry presentation. Presentation "chemical and physical phenomena"

CHEMICAL AND PHYSICAL PHENOMENA The purpose of the lesson:

• expand understanding of physical and chemical phenomena; establish what signs make it possible to distinguish physical phenomena from chemical ones;
• develop observation skills, the ability to competently handle substances;
• to cultivate attention, the ability to participate in the discussion, respecting the opinions of other people;

Phenomena Physical phenomena

melting

crystallization

condensation

evaporation

Physical phenomena in chemistry

Filtration

Distillation

Evaporation

Physical and chemical phenomena

LIGHTNING

Physical and chemical phenomena

Physical and chemical phenomena

Eruption

Physical and chemical phenomena

Physical and chemical phenomena

Leaves in autumn

Physical and chemical phenomena

Fire in the forest

Physical and chemical phenomena

Machine corrosion

Physical and chemical phenomena

melting ice

Physical and chemical phenomena

leaf rot

Physical and chemical phenomena

Sauerkraut

I AM IN L E N I

F Y Z I CH E S K I E

H I M I CH E S K I E

Signs of a chemical reaction

Release or absorption of heat

Change

Precipitation (dissolution) of the precipitate

Selection

Selection

Conditions for the occurrence and course of chemical reactions

catalyst

Heating

ultraviolet

exposure

Experience 1. Swimming paraffin.

A piece of paraffin was placed in a porcelain cup and heated. After melting the paraffin, the flame was extinguished. When the cup had cooled, the paraffin was examined.

Write down the observations (fill in the gaps in the sentences). What is this phenomenon?

Observations. When paraffin is heated, it ________, goes into the _____ state.

Conclusion: This is a _____________ phenomenon.

Experience 2. Evaporation of water.

Pour some water into a beaker and heat it up.

Observations: When heated, the water boiled, while changing its _________________

Conclusion: This is a _________________ phenomenon.

Based on the experiments, tell me what phenomenon is called physical?

PHYSICAL phenomena are called such phenomena in which these substances do not turn into others, there is a change in the state of aggregation of the substance or its form.

• H₂O - liquid - steam - ice

Experience 3. "Soda dissolution".

To a white crystalline substance (soda), we add acid (acetic vinegar). Record your observations. What is this phenomenon?

Observations. At the same time, there is a rapid release of _______. The ghost of transformation is the selection of _______.

Conclusion. This is a ____________________ phenomenon.

Experience 4. "Interaction of solutions".

Pour a blue salt solution (CuCl₂) and a colorless solution - NaOH into a test tube. Record your observations.

What is this phenomenon?

A sign of transformation is the loss of ____ and _____ colors.

Conclusion. This is a _________________ event.

Find a match. Option 1: Option 2:

• melting paraffin
• Rotting plant debris
• Metal forging
• Burning alcohol
• Souring apple juice
• Dissolving sugar in water
• Blackening of copper wire when annealed
• freezing water
• Souring milk
• frost formation

physical phenomenon

chemical phenomenon

2. Which of the phenomena are chemical?

1) freezing water

2) burning sulfur

3) decomposition of mercury oxide when heated

4) melting of metals

5) candle burning

6) air liquefaction

7) burning natural gas

1. Which of the phenomena are physical?

a) boiling water

b) decomposition of water by electric current

c) interaction of zinc with hydrochloric acid

d) metal melting

e) melting snow

e) decomposition of carbonic acid into carbon dioxide and water

g) freezing of water.

CHEMICAL AND PHYSICAL PHENOMENA

Physical: Chemical:

a–d–e–g 2–3–5–7

Homework Level I: - Read §25 and §26,

• Expand the essence of the basic concepts (p. 138);
• Answer orally questions #1-#6
(p. 139). Level III: the message "Chemical reactions in our kitchen" or a crossword puzzle, puzzles based on the material §25 and §26.

Thanks for being active in class!

Bibliography:

• Lightning - http://900igr.net/kartinka/pri
• Evaporation - http://www.edu54.ru/node/23215
• Volcanic eruption - http://video.nur.kz /vieut=3xjdf
• Frost - http://blog.privet.ru/user/pe
• Rain - http://pda.privet.ru/post/1251
• Leaf rot - http://modbiol.ru/forums/index
• Fog - http://anttila.ucoz.ru/forum/1
• Fire - http://www.kurer-sreda.ru/2011
• Melting ice - http://school.xvatit.com/index
• Corrosion of metals - http://www.pocketfives.com/f13
• Sauerkraut - http://www.liveinternet.ru/we
• Autumn leaves - http://2krota.ru/pictures/page
• Burning gas - http://vidomosti-ua.com/popula

>> Physical and chemical phenomena (chemical reactions). Experimenting at home. External effects in chemical reactions

Physical and chemical phenomena (chemical reactions)

The material of the paragraph will help you find out:

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

In the lessons of natural history, 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, therefore they are one substance (in different states of aggregation).

Phenomena in which a substance does not change into another is called physical.

Physical phenomena include not only the change of substances, but also the glow of hot bodies, the passage of 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. Consider the process of burning alcohol (Fig. 46). It occurs with the participation of oxygen, which is contained in the air. Burning, alcohol, it would seem, passes into a gaseous state, just as water turns into steam when heated. Ho it's not. If the gas obtained as a result of the combustion of alcohol is cooled, then part of it will condense into a liquid, but not into alcohol, but into water. The rest of the gas will remain. With the help of additional experience, it can be proved that this residue is carbon dioxide.

Rice. 46. ​​Burning alcohol

Thus the alcohol that burns, and oxygen, which is involved in the combustion process, are converted into water and carbon dioxide.

Phenomena in which one substance is converted into another, called chemical phenomena, or chemical reactions.

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

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

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, it creates heat. Under these conditions, the molecules of the reagents break down into atoms, which, when combined, form the 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 the interaction of substances are also known.

External effects accompanying chemical reactions.

By observing chemical reactions, you can fix the following effects:

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

Rice. 47. Some external effects in chemical reactions: a - the appearance
coloring; b - gas evolution; c - the appearance of sediment

Lab experience #3

The appearance of color as a result of the reaction

Are soda ash and phenolphthalein solutions colored?

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

Laboratory experiment No. 4

Emission of gas as a result of the reaction

Add a little hydrochloric acid to the soda ash solution. What are you watching?

Laboratory experiment No. 5

The appearance of a precipitate as a result of the reaction

Add 1 ml of copper sulphate 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 precisely a chemical phenomenon. Other external effects can also be observed during physical phenomena. Let's give some examples.

Example 1 Silver powder obtained in a test tube as a result of a chemical reaction has a gray color. If it is melted and then the melt is cooled, we get a piece of metal, but not gray, but white, with a characteristic luster.

Example 2 If natural water is heated, then gas bubbles will begin to be released from it long before boiling. It is dissolved air; its solubility in water decreases when heated.

Example 3. An unpleasant smell in the refrigerator disappears if silica gel granules, one of the Silicium compounds, are placed in it. Silica gel absorbs molecules of various substances without destroying them. Activated charcoal in a gas mask works similarly.

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

To determine whether a transformation has taken place - physical or chemical, one 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 are constantly taking place in nature. Substances dissolved in rivers, seas, oceans interact with each other, some react with oxygen. Plants absorb carbon dioxide from the atmosphere, from the soil - water, substances dissolved in it 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 annually, 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 the roasting of meat, vegetables, baking bread, souring of milk, fermentation of grape juice, bleaching of fabrics, burning various kinds fuel, hardening of cement and alabaster, blackening of silver jewelry over time, etc.

Chemical reactions form the basis of such technological processes as the production of metals from ores, the production of fertilizers, plastics, synthetic fibers, drugs, and others. important substances. By burning fuel, people provide themselves with heat and electricity. With the help of chemical reactions, toxic substances are neutralized, industrial and domestic waste is processed.

Certain reactions lead to negative consequences. Rusting of iron reduces the life of various mechanisms, equipment, Vehicle, leads to large losses of this metal. Fires destroy housing, industrial and cultural facilities, historical values. Most foods spoil due to their interaction with oxygen in the air; in this case, substances are formed that have bad smell, taste and are harmful to humans.

conclusions

Physical phenomena are phenomena in which each substance is preserved.

Chemical phenomena, or chemical reactions, are the transformations 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. Find a match:

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

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

102. Why do you think some 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 amounts of aqueous solutions of citric acid and baking soda. Pour together portions of both solutions into a separate beaker. What's happening?

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

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

Record the results of the experiments in a notebook and draw conclusions.

Popel P. P., Kriklya L. S., Chemistry: Pdruch. for 7 cells. zahalnosvit. navch. zakl. - K .: Exhibition Center "Academy", 2008. - 136 p.: il.

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