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

slide 6

Scheme of distillation column for oil distillation

Slide 7

Slide 8

Filtration

Slide 9

Separating funnel, separating a mixture of water and oil

Slide 10

Iodine sublimation

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Conditions for the occurrence and course of reactions

Contact of reactants Grinding and mixing Heating

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Signs of chemical reactions

Precipitation Evolution of gas Discoloration Appearance of odor Emission of heat (light) of the combustion reaction

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Reaction classification

Exothermic reactions take place with the release of heat Endothermic reactions take place with the absorption of heat

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1. How do physical phenomena differ from chemical phenomena? 2. Which of the following phenomena are physical and which are chemical:

in winter, frost draws patterns on glass on the window make dishes oxygen supports the burning of candles purification of natural water from impurities by filtering yellowing of foliage in autumn attraction of iron by a magnet iron rusts in humid air

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What phenomenon, physical or chemical, is referred to in the Russian proverb "Water wears away a stone." Is fire a physical or chemical phenomenon? What signs of a chemical phenomenon can be observed in this case?

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Homework

§25, 26 ex. 3.4 p. 134; exercise 1.2 p. 138 Reports on the application of physical and chemical phenomena.

Slide 17

Option 1 writes out the numbers of chemical phenomena, Option 2 - physical phenomena: Compression of a spring Formation of scale on the walls of the kettle Decay of plant residues Ice drift on the river Metal forging Souring of apple juice Appearance of plaque on copper and bronze monuments Charring of a splinter Freezing of water Souring of milk Burning of natural gas Formation of frost

Methodological development on the topic k, presented on, is a lesson in the formation of new methods of action, as well as knowledge at a basic level, according to the teaching materials through Gabrielyan O.S.

During the lesson, students' ideas about physical and chemical phenomena become wider, the ability to distinguish chemical reactions according to the corresponding signs is formed. The formation of skills for the safe and correct handling of laboratory equipment and substances is also continuing.

A favorable atmosphere is created in the classroom for the development of cognitive activity in eighth graders through the organization of a chemical experiment. Implemented in the classroom and educational goals. This is the instillation of tact, responsibility, and the education of observation, attention.

Physical and chemical phenomena - a description of the course of the lesson

In the process of frontal conversation with a demonstration, the knowledge of students in the lesson is updated. In the introductory part of the lesson, the teacher draws the attention of the class to the world around us, specifying that all objects, bodies, including us, consist of substances. Accompanied by a presentation slide the circumstance is explained that some phenomena, processes constantly occur with these substances.

The conversation is supported by questions such as:
How do some substances differ from others? ( properties such as taste, smell, color, etc.)
What is he studying? ( For example: studies the structure and properties of substances, as well as their application)

We update new knowledge by demonstrating several phenomena. Three students in the class, with the help of a teacher, conduct demonstration experiments offered to them by cards. The class needs to establish what kind of changes are observed with the properties of substances as a result of these experiments.

Demonstration of experiments confirming physical and chemical phenomena

Students will experience the following:
Experience 1 : Copper wire is twisted into a spiral on a pencil, and then straightened out. Question: - Did the properties of the copper wire change?
Experience 2 : A few drops of phenolphthalein indicator are added to a solution of sodium hydroxide (NaOH) in a test tube in an amount of 2 ml. Question: What do you observe and what has changed?
Experience 3 : A small piece of chalk is ground in a porcelain mortar. Question: - Have the properties of chalk changed?

During the conversation and answers to the above questions, the attention of students is focused on changing the particle size and shape of the substance, its color before and after the experiment. Thus, step by step, eighth graders realize the principle according to which the observed processes can be divided into two groups, based on their reversibility and irreversibility. Thus, reversible phenomena are primarily associated with the physical properties, and irreversible - with the chemical properties of substances.

The class begins the study of new material by considering the explanatory characteristics of physical phenomena. This time, a natural phenomenon is taken as an example - the cycle. To the illustration of the water cycle in nature shown on the screen, the teacher asks the question: What physical processes take place as a result of the water cycle?

In the course of reasoning, we come with the guys to the conclusion that in all known physical processes only the aggregate state of matter changes, while the composition remains unchanged. So, in the water cycle, the composition - water molecules - does not change. There is only a transition from one state of aggregation to another.

One of the clear examples of a change in the state of aggregation is the melting of paraffin, the video clip of which is shown to the class (the link to the video of the experiment is on the presentation slide , as in the case of other experiments proposed in this development of the lesson).

Examples of physical and chemical phenomena

Another example of a change in the state of aggregation is sublimation, when a substance passes from a solid, bypassing the liquid phase, immediately into a gaseous state. We watch a video clip of the sublimation of benzoic acid, which first passes into the gaseous phase ( smoke), and then it crystallizes on a coniferous branch.

Thus, physical phenomena are very widely used by man in activities: filtering ( drinking water treatment), distillation ( receiving oil products), evaporation ( obtaining from solutions of solids), upholding and much more. And again it is concluded that physical phenomena are associated with changes in the shape of the body, its size, as well as the state of aggregation of matter.

Completing the block, the class proceeds to the second part of the lesson, where attention is focused on the main features of chemical phenomena. Video clips of the experiments are observed and discussed here:

"Pharaoh Serpent", where nitroacetylenide reacts with sulfuric acid, with the formation of a precipitate, the evolution of gases and a change in the color of the solution;
"Vibrational Briggs-Rauscher Reaction", during which the color of the solution changes over several minutes;
spontaneous combustion of paraffin as a result of its melting and heating to the boiling point;
"volcano" in the decomposition of ammonium dichromate.

Consolidation of material on physical and chemical phenomena

According to differentiated tasks, the material is consolidated and reflection is carried out. And the lesson ends with a laboratory workshop, which the author of the methodological development proposes to conduct in groups. Each group makes and describes their experience, and the algorithm for its implementation is printed out in advance and distributed to the class.