Practical work: obtaining ethylene and studying its properties. Laboratory work in chemistry "Qualitative determination of carbon in organic substances

29.09.2019

Chemistry is an experimental science, therefore, students always treat any type of experiment used in the lesson with great attention, interest, and curiosity, especially if it is practical work. In my methodology, I very often use conducting and showing demonstration experiments directly to students.

This lesson was developed for grade 10 information technology profile (1 hour).

Educational goals:

consolidation, application and assessment of students’ knowledge about the laboratory method for obtaining alkenes;
creating conditions for the formation and development of experimental skills of students;
formation of an integral knowledge system.

Educational goals:

the formation of communicative and information competencies of schoolchildren through the organization of work in a group;
cultivate responsibility when working in a team, diligence;
to form the traits of a socially oriented personality of students.

Developmental goals:

continue the formation of basic mental operations (analysis, synthesis, comparison, abstraction);
promote the development of a creative approach to learning.

Tasks:

know the laboratory method for producing ethylene, safety rules when working with organic substances and concentrated sulfuric acid;
be able to practically obtain ethylene and prove it properties (uncertainty) characteristic reactions ;
be able to write reaction equations , proving the properties of ethylene, make observations, draw conclusions, follow safety rules when working in the chemistry classroom.

Lesson type: application of knowledge in practice

Lesson format: workshop lesson.

Lesson structure involves the following stages: organizational, goal setting, checking homework and updating knowledge, operating knowledge, skills and abilities when solving practical problems, drawing up a report on the completion of work, determining homework. In this lesson, students, based on previously acquired knowledge, engage in practical activities. First, homework is checked, then theoretical material is analyzed in order to update knowledge. After this, students are involved in carrying out constructive tasks that have a pronounced practical orientation.

Form of organization of student activities: individual work and work in groups.

Basic units of knowledge: laboratory method for producing ethylene; qualitative reactions to unsaturated hydrocarbons of the ethylene series.

Teaching methods:

verbal;
visual;
practical;
application of knowledge;
formation of skills and abilities;
creative activity;
instructive and practical.

Means of education:

textbook N.E. Kuznetsova, Titova I.M., Gara N.N. Chemistry: textbook for grade 10;
electronic manual - Virtual Laboratory (chemistry grades 8-11);
safety review questions (PowerPoint);
projector;
screen;
laptop;
guide cards for 4 groups, 4 options;
5 laptops;
poster: “Work with chemical equipment carefully! Handle concentrated sulfuric acid H2SO4 with care!”;
concentrated sulfuric acid – H 2 SO 4;
potassium permanganate solution – KMnO 4
tripod;
measuring cylinder;
test tubes;
measuring spoon;
test tube holder;
alcohol lamp;
calcined river sand;
ethyl alcohol – C 2 H 5 OH;
bromine water Br 2 (aq);
gas outlet pipe;
matches;
crucible cover.

During the classes:

At home, the children studied Practical Work No. 1 on their own using the textbook p. 102.

During the lesson, students perform practical work individually in an electronic manual (5 people) using laptops and experimentally in groups (4 groups of 4 people).

The teacher differentiates the work of the children - individually and according to guide cards - 2.4 students with a high level of learning ability work (the third level is indicators by which one can judge the levels of development of students, R.V. Shilenkov and G.M. Chernobelskaya identify three main level of students' knowledge acquisition), according to guide cards 3 - with average (second level), according to guide cards - 1 - low (first level).

**1. Preparation for practical work ( organizational stage ).**

Annex 1 Microsoft PowerPoint .

Questions ( updating knowledge ) about safety rules when working with organic substances and behavior in the chemistry classroom (you can use the electronic manual - Virtual Laboratory (chemistry grades 8-11).

Question 1 .

Should the end of the gas outlet tube be removed from the test tube with a solution, for example potassium permanganate, without stopping the heating of the mixture of H 2 SO 4 and C 2 H 5 OH?

no, it is not necessary to follow this rule;
This should not be done, because the danger of destruction of the reactor tube increases;
yes, because when the reactor test tube is cooled, a vacuum is created and a cold solution entering a hot test tube will lead to its destruction;
yes, because the mixture in the reactor tube must cool gradually, otherwise an explosion is possible.

Question 2.

Why are boiling stones added to a mixture of ethyl alcohol and concentrated sulfuric acid?

for more uniform boiling;
boiling stones protect the mixture from overheating;
to increase the volume of the mixture;
boiling stones play the role of a catalyst.

Question 3.

How to properly prepare the reaction mixture (a mixture of ethyl alcohol and concentrated sulfuric acid)?

Question 4.

Comment on the image “heating a liquid in a test tube.”

Review of basic safety rules.

**2. Conversation about the progress of the work, using guide cards, recording the purpose of the work (*checking homework, setting goals*** ) .

Goal of the work: learn how to produce ethylene in the laboratory and carry out high-quality reactions on unsaturated hydrocarbons of the ethylene series.

**3. Conducting practical work (*operating knowledge, skills and abilities*** ) .

4 groups of students received a guide card and began to do the work.

5 students work individually with laptops, in the electronic manual - Virtual Laboratory (chemistry 8-11 grades), perform the work “Production of ethylene”, prepare a report in a personal journal.

Each student also has a guide card; each card contains a problematic question or task to which a detailed answer must be given.

It is also possible another variant conducting practical work (if laptops are available, on the advice of students): students work in a group experimentally and using an electronic manual, but the group consists of no more than 4 people.

(Appendix 2 - Microsoft Word ).

4. Drawing up and aboutreport preparationabout doing work in groups(Appendix 3 - Microsoft Word ).

5. Drawing up and aboutreport preparationabout performing work individually in the electronic manual

(Appendix 4 - MicrosoftPowerPoint).

6. Homework:

§16 pp. 100-101, using the Internet, resources, offer your laboratory experiments on the production of ethylene:
http://www.alhimik.ru/read/grosse11.html
http://www.alhimik.ru/ucheba/apparatus2.html - Chemistry room. Equipment. Instruments and accessories for chemical experiments.
XuMuK.ru!

Task. A mixture of ethane and ethylene with a volume of 0.8 l (n.s.) decolorized 200 g of bromine water with a mass fraction of 1.6%. Determine the volume fraction of each gas in the mixture.

Practical work is completed, students in groups hand over notebooks for practical work for verification, students who did the work independently mark - Last name, First name, class, registration password.

7. Analysis of practical work “Production of ethylene and experiments with it.”

Students of specialized classes coped with this practical work very well. The experimental part of the work did not cause any difficulties. The difficulty arose with one group working with guide card -2, the guys found it difficult to answer the question: why did the reaction mixture turn black?

Having studied student reflection, I know that motivation to study further topics in organic chemistry has increased.

Many of the guys noted as a difficulty that they were afraid to ignite the released gas on their own or warm up the test tube with the reaction mixture, because. The mixture contains concentrated sulfuric acid, the properties of which they studied very well in the 9th grade.

I was surprised, a simple human thing - THANK YOU FOR THE LESSON!

The most interesting thing for me is that one group of children proposed to carry out this practical work both experimentally and electronically; I liked this proposal and will follow the advice of the 10th graders next school year.

Practical work No. 1 “Obtaining ethylene and studying its properties”

Goal of the work: obtain ethylene and study its chemical properties.

Reagents and equipment: laboratory stand, stand with test tubes, stopper with gas outlet tube, video film “Production of ethylene”, alcohol lamp, matches, H solutions 2 SO 4, KMnO 4, bromine water.

Progress

Experiment 1. Production of ethylene

In a test tube with 2 ml ethanol C 2 H 5 OH add 6 ml concentrated sulfuric acid H 2 SO 4 . Pour 1 spoon of calcined sand into the test tube, close it with a stopper with a gas outlet tube, secure it in a stand and start heating.

Note the changes in the test tube with the reaction mixture. Write down the reaction equation for the production of ethylene using abbreviated structural formulas. Draw a conclusion from what substances ethylene can be obtained in the laboratory.

Experiment 2. Interaction with bromine

Place the end of the gas outlet tube into a test tube with 2 ml of bromine water (bromine solution Br 2 in water).

How did the color of bromine water change? Write the reaction equation using abbreviated structural formulas. Conclude whether there is a double bond in the ethylene molecule.

Experiment 3. Interaction with potassium permanganate

Place the end of the gas outlet tube into a test tube with 2 ml of potassium permanganate solution KMnO 4 .

How did the color of the potassium permanganate solution change? Write the reaction equation using abbreviated structural formulas. Conclude whether there is a multiple bond in the ethylene molecule.

Experiment 4. Combustion of ethylene

Ignite the released gas.

What color does ethylene burn? Write the reaction equation using empirical formulas. Draw a conclusion about what substances are formed as a result of the combustion of alkenes.

Registration of work

Based on the results of the experiment, fill out the table:

Write down your general conclusion about the practical work.

Conclusion: ethylene can be obtained in the laboratory by the interaction of ___________; Ethylene is a __________ hydrocarbon.

On the topic: methodological developments, presentations and notes

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Practical work No. 2

Obtaining ethylene and studying its properties

Purpose of the work: experimentally obtain ethylene, carry out qualitative reactions proving the unsaturated nature of ethylene; improve the ability to obtain gaseous substances.

Equipment and reagents: metal stand, laboratory stand with test tubes, alcohol lamp, matches, stopper with gas outlet tube, porcelain cup, crucible tongs, mixture of ethanol and concentrated sulfuric acid, solutions of potassium permanganate, bromine water, clean sand or pieces of porous ceramics.

Experimental task I. Level I

Production of ethylene.


Executor	Experimental task I	Commentator

	Ethylene is obtained by heating a mixture of ethyl alcohol C 2 H 5 OH and sulfuric acid H 2 SO 4.
	To do this, pour 1 ml of alcohol and 3 ml of concentrated sulfuric acid into a test tube.
	TB: It is the acid that should be added to the alcohol, and not vice versa, and the acid should be added gradually, stirring the mixture in a test tube.
	Add 1-2 spatulas of clean sand or a piece of porous ceramic to the test tube to ensure uniform boiling of the mixture.
	We close the test tube with a stopper with a gas outlet tube.
	We fix the test tube obliquely in the holder foot on a tripod, as shown in the figure, and carefully heat it.
	We immediately begin to study the properties of the released gas! (experimental task II, III).

Experimental task I. Level II

Production of ethylene.

Experimental task I. Level III

Ethylene production

For the experiment, we assemble a device for producing gases, in accordance with the figure.

Ethylene is produced by heating a mixture of _________ and _________________.

To do this, pour 1 ml of ________ and 3 ml of concentrated ______________ into a test tube.

Add 1-2 spatulas of clean sand or a piece of porous ceramic to the test tube to _____________________.

We close the test tube with a stopper with a gas outlet tube.

We fix the test tube obliquely in the holder foot on a tripod, as shown in the figure, and carefully heat it.

We immediately begin to study the properties of the released gas! (experimental task II, III).

Experimental task I. Level IV

Obtain ethylene from ethyl alcohol and sulfuric acid using the figure.

Experimental task II. Level I

Properties of ethylene.

Pour 2–3 ml of a solution of potassium permanganate KMnO4 and bromine water into two clean test tubes (we get them from the teacher or laboratory assistant).

Similarly, we pass the gas through a solution of potassium permanganate KMnO 4 .

We observe the discoloration of the solution of potassium permanganate KMnO 4 as the gas passes through.

Conclusion: ethylene reacts with a solution of potassium permanganate KMnO4.

Topic: Obtaining ethylene and studying its properties
Executor	Experimental task II	Commentator
	Pour 2–3 ml of a solution of potassium permanganate KMnO4 and bromine water into two clean test tubes (we get them from the teacher or laboratory assistant).
	We lower the gas outlet tube first to the bottom of the test tube with bromine water.
	We pass the released gas through it.
	We observe the discoloration of bromine water as the gas passes through.
	Conclusion: ethylene reacts with bromine water.
	Similarly, we pass the gas through a solution of potassium permanganate KMnO4.
	We observe the discoloration of the solution of potassium permanganate KMnO4 as the gas passes through.

	Conclusion: ethylene reacts with a solution of potassium permanganate KMnO4.
	We leave the solutions for comparison.

Experimental task II. Level II

Properties of ethylene.

We lower the gas outlet tube first to the bottom of the test tube with bromine water.

We pass the released gas through it.

Conclusion: ethylene reacts with bromine water.

We observe as the gas passes ______________ solution of potassium permanganate KMnO 4 .

Conclusion: ethylene reacts with a solution of potassium permanganate.

We leave the solutions for comparison.

Experimental task II. Level III

Properties of ethylene.

Pour 2-3 ml of a solution of potassium permanganate and bromine water into two clean test tubes (we get them from the teacher or laboratory assistant).

We lower the gas outlet tube first to the bottom of the test tube with bromine water.

We pass the released gas through it.

We observe as the gas passes ____________ bromine water.

Conclusion: ethylene interacts with ______________.

Similarly, we pass the gas through a solution of potassium permanganate.

We observe as the gas passes ______________ potassium permanganate solution.

Conclusion: ethylene reacts with the solution __________________.

We leave the solutions for comparison.

Experimental task II. Level IV

React ethylene with bromine water and a solution of potassium permanganate.

Experimental task III. Level I

We conclude: the color of the flame is lighter in comparison with household gas, which indicates an increase in the mass fraction of carbon in unsaturated hydrocarbons in comparison with saturated hydrocarbons.

We observe the formation of a black soot spot, the appearance of which can be explained by the high content (%) of carbon in the ethylene molecule and its incomplete oxidation:

H 2 C = CH 2 + O 2 -> CO 2 + C + H 2 O + CO

Topic: Obtaining ethylene and studying its properties
Executor	Experimental task III	Commentator
	We direct the end of the gas outlet tube with the released ethylene vertically upward.
	We ignite the escaping gas with matches.
	We observe that the color and brightness of the glow of an ethylene flame differs from the flame of ordinary household gas, which is a mixture of propane and butane.
	We conclude: the color of the flame is lighter in comparison with household gas (natural, consisting of 80% CH 4), which indicates an increase in the mass fraction of carbon in unsaturated hydrocarbons in comparison with saturated ones.
	We bring a porcelain cup secured in crucible tongs to the top of the flame.
	We observe the formation of a black soot spot, the appearance of which can be explained by the high content (%) of carbon in the ethylene molecule and its incomplete oxidation: H 2 C = CH 2 + O 2 -> CO 2 + C + H2O + CO
	Let's get the workplace in order.

Experimental task III. Level II

Study of ethylene flame properties.

We direct the end of the gas outlet tube with the released ethylene vertically upward.

We ignite the escaping gas with matches.

We observe that the color and brightness of the glow of an ethylene flame differs from the flame of ordinary household gas (natural, consisting of 80% CH 4), which is a mixture of propane and butane.

We conclude: the color of the flame is _____________ in comparison with household gas, which indicates an increase in the mass fraction of carbon in unsaturated hydrocarbons in comparison with saturated ones.

We bring a porcelain cup secured in crucible tongs to the top of the flame.

We observe the formation of _________ soot spots, the appearance of which can be explained by the high content (%) of carbon in the ethylene molecule and its incomplete oxidation:

H 2 C = CH 2 + O 2 -> CO 2 + C + H 2 O + CO

Experimental task III. Level III

Study of ethylene flame properties.

We direct the end of the gas outlet tube with the released ethylene vertically upward.

We ignite the escaping gas with matches.

We observe that the color and brightness of the glow of an ethylene flame from the flame of ordinary household gas, which is a mixture of propane and butane, ______________.

We conclude: the color of the flame is _____________ in comparison with household gas, which indicates an increase in the mass fraction of ___________ in unsaturated hydrocarbons in comparison with __________________.

We bring a porcelain cup to the top of the flame.

We observe the formation of _________ spots of soot, the appearance of which can be explained by a higher content (%) of the element _________ in the ethylene molecule and its incomplete oxidation.

Experimental task III. Level IV

Study the properties of an ethylene flame using: 1) a household gas flame in comparison, 2) a porcelain cup.

Reporting tasks

Option 1

What is the role of sulfuric acid in the reaction to produce ethylene?

How can you experimentally clean propane from butene-1 impurities?

List the provisions of the safety rules when performing experiment No. 1.

Write a chemical equation for the production of ethylene.

Option 2

How to experimentally distinguish ethylene from ethane?

How can you experimentally purify butene from butene-1 impurities?

Give an assessment to each member of your group (how successfully they coped with their roles, positive aspects, shortcomings).

List the provisions of the safety rules when performing experiment No. 2.

Write an equation for the chemical reaction between ethylene and potassium permanganate.

Record the progress, observations and conclusions of the experiments in your notebook.

Option 3

Do the properties of alkenes depend on the symmetrical structure of the molecules? Give examples.

How can you experimentally purify butane from pentene-1 impurities?

Give an assessment to each member of your group (how successfully they coped with their roles, positive aspects, shortcomings).

List the provisions of the safety rules when performing experiment No. 3.

Write an equation for the chemical reaction between ethylene and iodine water.

Record the progress, observations and conclusions of the experiments in your notebook

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“Chemistry 10th grade Practical work No. 2. "Preparation of ethylene and experiments with it""

Practical work 2.

“Preparation of ethylene and experiments with it”

Target:

consolidate students' knowledge on the topic “Alkanes. Alkenes”, teach how to produce ethylene and conduct experiments with it;

improve the ability to obtain gaseous substances in the simplest devices, observing safety regulations;

foster a sense of responsibility and collectivism.

Equipment: on the students' tables: a laboratory stand with a foot, an alcohol lamp, matches, test tubes in a stand, a gas outlet tube, sand, bromine water, a solution of potassium permanganate, ethyl alcohol, concentrated sulfuric acid.

During the classes

1. Safety briefing against signature.

Then together we analyze the progress of practical work point by point, stopping

in detail on extreme caution when carrying out practical work.

2. Students begin to draw up practical work in notebooks for

practical work: write down the number, topic, purpose, equipment.

3. Then they do practical work. An issued test tube with a ready-made

a mixture of ethyl alcohol (2 - 3 ml), concentrated sulfuric acid

(6 - 9 ml) and calcined sand, close with a gas outlet tube, strengthen

in a laboratory stand and begin to heat it carefully, starting with warming up

the entire test tube.

a) C 2 H 5 OH → H 2 C = CH 2 + H 2 O

ethyl alcohol ethylene

The end of the gas outlet tube is lowered into a test tube into which 2-3 ml is poured

bromine water. After some time, the released gas discolors

bromine water. This means that a chemical reaction occurred and formed

new substance:

b) H 2 C = CH 2 + Br 2 → CH 2 Br – CH 2 Br

ethylene 1,2 – dibromoethane

4. After the bromine water has become colorless, pour 2-3 ml into another test tube

dilute solution of potassium permanganate acidified with sulfuric acid,

and also pass the resulting gas through it. Over time

the color disappears, the solution becomes transparent, which means also here

a chemical reaction occurred and a new substance was formed:

H 2 C = CH 2 + [O] + H 2 O → CH 2 – CH 2

ethylene ׀ ׀

ethylene glycol

5. After the experiments have been completed, remove the gas outlet tube from the test tube and

Set the released gas on fire, it burns with a luminous flame. Ethylene, like everyone else

hydrocarbons burn to form carbon dioxide and water:

C 2 H 4 +3O 2 → 2CO 2 + 2H 2 O

6. After finishing work, clean up the desktop and begin

designing the work in a notebook: describe the entire progress of the work, sketch

Figure 19 on page 56, as you work write the equations of the corresponding

reactions, at the end of the work draw a conclusion, while answering all questions for

independent conclusions; at the end of the lesson, notebooks are submitted for checking.

Chemistry lesson in 10th grade

Practical work No. 2.

"Preparation of ethylene and experiments with it."

Target: consolidate students' knowledge on the topic “Alkanes. Alkenes”, teach how to produce ethylene and conduct experiments with it; improve the ability to obtain gaseous substances in the simplest devices, observing safety regulations.

Planned learning outcomes: be able to conduct experiments on the production of ethylene and study its properties, observe safety rules when working with substances, equipment and chemical utensils, and write a report on practical work.

Equipment: on the students' tables: a laboratory stand with a foot, an alcohol lamp, matches, test tubes in a stand, a gas outlet tube, sand.

Reagents: bromine water, potassium permanganate solution, ethyl alcohol, concentrated sulfuric acid.

Lesson type: laboratory-practical.

Lesson structure.

I . Repetition of learned material.