Lesson topic: Mass fraction of a chemical element in a compound chemistry lesson plan (8th grade) on the topic. Calculation of the mass fraction of chemical elements according to the formula of a substance Mass fraction of a chemical element in a compound abstract

Lesson topic: Mass fraction chemical element in connection

ω, ω%

Target: Adaptation of the concept of fraction to the subject of chemistry when solving problems with environmental content to find the mass fraction of an element in a chemical compound.

Tasks:

1. Form the concept of the mass fraction of an element;
2. Develop skills in finding the mass fraction of an element in a chemical compound;
3. Develop a personality with an ecological way of thinking.

Equipment:

1. Multimedia projector;
2. Computer;
3. Cards;
4. The flyleaf of the textbook with the table of D.I. Mendeleev;
5. Notebooks;
6. Markers;
7. Table of D.I. Mendeleev;
8. Leaflets with numbers;
9. Globe.

During the classes

Epigraph for the lesson:

Don't let your soul be lazy
So as not to pound water in a mortar,
The soul must work day and night,
Both day and night! (M. Zabolotsky).

1.Organizing time. There is a globe on the display table.

Teacher's words: The components of our planet are the organic and inorganic world, formed by organic and inorganic substances. Look at the globe.

71% of our planet is occupied by matter, without which there would be no life on our earth. What is this substance? (water) You already know that any substance can be written using a chemical formula. (The multimedia projector turns on, the formula H is displayed on the screen 2 O). What can you determine from this formula?

Student answers (qualitative and quantitative composition, simple or complex substance, determine what kind of substance it is, find M r).

Teacher's words: Guys, what elements make up a water molecule? (hydrogen and oxygen). How many atoms of each element are there in a water molecule? (student answers) And if you change the number of oxygen or hydrogen atoms in a water molecule, will the changed formula belong to the substance water (student answers)? And so, the atoms of chemical elements are located in a molecule in certain mass ratios, i.e. constitute a certain part of the total molecule. How can you calculate what part of a molecule is a chemical element (student suggestions)?

With your help, we determined the topic of our lesson: “Calculating the mass fraction of an element in a compound.”

What do you think is the purpose of our lesson (students determine the purpose of the lesson)?

You have a certain amount of knowledge, what concepts previously studied will help you achieve your goal (chemical element, chemical formula, relative atomic and molecular mass, fraction)?

Let's see if you are ready to learn new material. Let's carry out the relay race between the rows.

Students write down the names of chemical elements on a piece of paper. Each student writes down only one chemical sign and hands the card to his friend. The first group to complete the task raises their hand. The teacher shows the symbols of the signs of chemical elements, and the students are the last in the group to check the correctness of the task (each student in the row receives 2 points if there are no errors, an additional point is the row that completed the task first (if there are no errors) and 0 points for the student who does not know chemical signs).

We complete the second task (3 points) individually. Four options.

Find the relative molecular weight:

I CO 2

II Na 2 O

III NO 2

IV Na 2 O 2

(students work in notebooks) If the problem is solved correctly, the student receives three points, if a mathematical error is made - 1 point, and if the solution is incorrect - 0 points. The total number of points for the two tasks is calculated.

We have repeated the necessary definitions, chemical elements, molecular weight, but what does the concept of fraction mean? Let's repeat the concept by solving problems on finding a fraction.

(A slide appears on the screen depicting a flask with round and square molecules)

Task No. 1

What is the proportion of square molecules in the flask? (students solve and compare their solution with the solution proposed by the teacher and shown on the slide)

Solution: there are only 7 molecules, square 3. Their fraction is 3/7 or 0.4286 or 42.86%

Problem No. 2

What is the area fraction of the green rectangle? (accompanied by the following slide, showing two rectangles. The area of ​​one is 10 cm 2, green 2cm 2)

Solution: 2/10 or 0.2 or 20%.

Problem No. 3

A green ball weighs 1 kg, a red ball weighs 10 kg (slide showing red and green balls in a box and the solution to the problem). What is the proportion of green marbles in the box?

Solution: each green ball weighs 1 kg, and there are two of them, which means a total of 2 kg of green balls. The total mass of the balls is 12 kg, which means 2/12 or 0.1667 or 16.67.

All students actively participating in solving problems add 1 point.

Teacher's words: ( demonstration of the followingslide showing a diagram of a water molecule) Consider a water molecule. You can find the mass of these balls in D.I. Mendeleev’s table of chemical elements. And so the mass fraction of oxygen? Try to solve the problem yourself, get acquainted with the algorithm for solving problems. Who didn't make it? Students can get help from a teacher or classmate. The solution is checked on a pre-prepared slide.

Students who complete the task independently receive 2 points, the rest receive one.

Teacher's words: In your geography lesson, you studied the main sources of water pollution. Name them. What conclusion should we draw?

The teacher focuses on knowing the formula for finding the mass fraction of an element. This formula appears on the slide and is read by students.

Teacher's words : Why does a person need to know the mass fraction?

Let's imagine that each of us has our own metallurgical plant. To obtain iron you need to purchase ore. Which ore is more profitable for you to buy? Fe 3 O 4 or FeO?. This task is best solved in pairs. One student finds the mass fraction of iron in Fe ore 3 O 4, the other FeO and compare the mass fractions.

Teacher's words : Does the ore mining process affect environment? Conversation with students.

Teacher's words: you have solved a difficult problem. But you may face more important challenges in life. Mass fraction is one way of expressing concentration, and this factor is very important for human activity. Your comrades have prepared messages, let's listen to them.

Message #1

Message #2

Teacher's words:

Students solve the problem. Next, the teacher reports that when the mineral cinnabar is heated, mercury is released in the form of vapor. In warehouse 1000m 3 where there was 100 kg of cinnabar, a fire broke out. Assess the danger of the situation using the data from the previous task (this task is solved independently or with the help of the teacher, depending on the level of preparedness of the class). Students receive 3 points for solving this problem.

Teacher's words: Guys, why do you think I chose the words of the Russian writer M. Zabolotsky as the epigraph for the lesson? There are no people to whom knowledge comes on its own; only systematic work raises them a step higher every day. If you are unhappy with yourself today, don’t be upset, work at home on your own and tomorrow you will succeed. Give yourself a grade of “5” if you scored 9 points or more, “4” - 7-8 points, “3” - 5-6 points, if you scored less than 5 points, we will receive a grade in the next lesson.

Message #1

Carbon dioxide is a colorless gas with a sour odor and taste, used in Food Industry for the production of sugar, lemonade. Participates in the process of photosynthesis. But if its proportion in the air is more than 2.5%, then it causes poisoning of the body and can lead to death. Content increases carbon dioxide in the atmosphere more than 0.03% can lead to an increase in temperature on our planet, i.e. to global changes.

Message #2

Mercury is a highly toxic metal that affects the hematopoietic, central nervous system, kidneys. In the body, mercury compounds penetrate into various organs and tissues, but most of all they are found in the blood, liver, kidneys, and brain. Mercury vapor tends to spread evenly throughout the entire volume, accumulating in tissues. If in a small room (2m 3 ) its vapor will be 0.02 mg, then the damage to human health will be great.

Task No. 1

What is the proportion of square molecules in the flask?

Problem No. 2

What is the area fraction of the green rectangle? The area of ​​one is 10 cm 2, green 2cm 2

Problem No. 3

The green ball weighs 1 kg, the red ball weighs 10 kg What is the proportion of green balls in the box?

Problem No. 4

The mineral cinnabar exists in nature. Determine the mass fraction of mercury in cinnabar (HgS).

MBOU secondary school No. 139 of the Samara city district.

Chemistry lesson notes for grade 8.

Subject: Chemical formulas. Relative atomic and molecular masses. Mass fraction of an element in a compound.

Lesson Objectives

 educational:

Learn the concepts: chemical formula, index, coefficient; writing and reading formulas.

Explore the differences between relative, atomic and molecular masses;

Learn the concept of mass fraction of a chemical element and learn how to calculate it.

 developing:

To develop in students the ability to make simple, logical constructions based on chemical knowledge;

Develop the ability to use in non-standard situations research activities knowledge from various sections of school disciplines (physics, algebra), if necessary, find missing information in reference and educational literature;

 educational:

To cultivate personal reflection, that is, the ability to comprehend one’s actions and oneself in a problematic research situation;

To foster self-organization and self-esteem in students when performing research assignments in class.

Equipment: tables “Relative atomic and molecular masses”, individual task cards for students, table by D.I. Mendeleev.

During the classes

I. Organizational moment

The teacher sets up the students to work during the lesson. Explains all stages of the lesson and students' actions at each of them.

Guys, today each of you will become a researcher and will “gain new knowledge”: find out the composition of chemical formulas, the rules for writing and reading them; derive the formula for the mass fraction of a chemical element and calculate it.

II. Studying new topic

1. The teacher's word.

Each atom of any chemical element has its own mass, just like any physical body surrounding us, including you and me. But unlike us, the mass of atoms is very small. Therefore, scientists took the mass as a standard 1/12 the mass of a carbon atom 6 12 WITH(as the lightest) and the mass of the remaining atoms was compared with the mass of this standard, hence the name “Relative atomic mass” from the English. « relative» relative. This quantity has no units of measurement and is designated Ar. The numerical value of the relative atomic mass of any element is written in the periodic table by D.I. Mendeleev.

If a substance is formed by several elements (identical or different), then we are talking about molecules and “Molecular relative mass”. She folds up from atomic masses everyone chemical elements that form a molecule, multiplied by the number of these atoms. It also has no units of measurement and is designatedMr. For example:

Mr (O 2) = Ar (O) 2 = 16 2 = 32;

Mr (H 2 O) = Ar (H) 2 + Ar (O) = 1 2 +16 = 18;

Mr (H 2 SO 4) = Ar (H) 2 + Ar (S) + Ar (O) 4 = 1 2 + 32 + 16 4 = 98;

The teacher repeatedly reminds students that the meaning Ar is found in periodic table DI. Mendeleev under the sign of a chemical element. The values ​​of the atomic masses of different chemical elements are added together. If there are several identical atoms in a molecule, their numerical value of atomic masses is multiplied by the number of these atoms. (a new topic will be reinforced when doing independent work in the research part of the lesson)

2. Research part (independent work students under the guidance of the teacher), if difficulties arise among students, the teacher must be very careful and under no circumstances give students a direct correct answer, that is, “ready-made knowledge” they must obtain it themselves. It is better to “push” the student to the right decision leading questions that stimulate mental activity, the need to connect existing knowledge from other areas with new material. This is necessary in order not to disrupt the students’ research process and to achieve the best results when learning new material, since knowledge acquired independently is retained in long-term memory than ready-made information.

Sample questions:

- How do you think?

- Imagine what will change if...?

- How will it change and what does it mean?

- Think about where else have you come across this concept? etc.

The teacher distributes task cards to the students, focusing their attention on the fact that this is an independent research, but if necessary, you (the teacher) will definitely help and guide the work of each student in the right direction.

Cards - tasks

Subject: Chemical formula. Relative, atomic and molecular masses. Mass fraction of chemical elements.

Conditional composition record chemical substance, using symbols of chemical elements, indices and coefficients - called a chemical formula

Task 1. Chemical formula, its composition, writing and pronunciation.

A. Explore the qualitative and quantitative composition of chemical formulas. Analyze what each of them means in the formula.

Formula

Formula

Conclusions:

1) High-quality composition chemical formula shows: _____________________________________ form a substance.

2) Quantitative composition chemical formula shows:

Form a substance.

IN. Analyze the entry and see what you think the index and coefficient in the chemical formula show.

2 Al 2 O 3

coefficient index

index – this is _____________, which shows the _______________ in a substance, written by the ______________________ symbol of a chemical element;

coefficient – this is _______________, which shows the amount of _____________ chemical substance, written by ______________ chemical formula;

IN. Explore the rules for reading formulas.

Formula The order of pronunciation of the components of the formula:

1. coefficient

2. symbol of the chemical element * and its index (if any.)

3.next symbol of the chemical element and its index.

* When reading a chemical formula, the pronunciation of the symbol of the chemical element is read, not its name.

Independent work.

(consolidation of new material)

1.1. Write down the qualitative composition of each formula:

H 2 SO 4 _______________ FeSO 3 _____________________

H 3 PO 4 ________________ H 2 Cl 2 O 7 ____________________

1.2. Write down the quantitative composition of each formula:

O 3 __________________ K 2 O _______________________

Cl 2 __________________ MgCO 3 ____________________

MgO ________________ NaOH _____________________

H 2 SO 4 _______________ FeSO 3 _____________________

H 3 PO 4 ________________ H 2 Cl 2 O 7 ____________________

1.3. Read the formulas. Write down what you got:

Li 2 O ___________________________________________________

CaS ___________________________________________________

H 2 SiO 3 _________________________________________________

MgSO 4 _________________________________________________

Task 2. Dependence of the mass fraction of elements in a compound on some physical quantities.

Analyze on what parameters and how the mass fraction of an element in a compound depends.

A. Explore the composition and relative atomic masses of the elements of the hydrogen chloride molecule HCl.

Compare the mass fractions of elements in the compound:  ( H) _________  (Cl)

( ,  ,  )

(direct/reverse)

B. Explore the composition of ethane molecules C 2 H 6 and acetylene C 2 H 2.

Compound

Compare mass fractions hydrogen in ethane and acetylene:

 (H) C 2 H 6 _______________  (H)C2H2

( ,  ,  )

What parameter and how does it affect the value of the mass fraction of an element in a compound?

The mass fraction of an element in a compound is _________________proportional(direct/reverse) the value _____________________________________ of this element.

IN. Explore the composition of the carbon dioxide molecule CO 2 and carbon monoxide CO.

Compound

Compare the mass fractions of carbon in carbon dioxide and carbon monoxide:

 (C) CO 2 _____________  (C) CO

( ,  ,  )

What parameter and how does it affect the value of the mass fraction of an element in a compound?

The mass fraction of an element in a compound is _________________proportional(direct/reverse) the value _____________________________________ of this element.

Summarize your conclusions and create a formula showing the dependence of the mass fraction on the parameters you found. For this:

Write directly proportional values ​​into the numerator

mass fraction value

Options

Write inversely proportional in the denominator

mass fraction value

 (E) % = ––––––––––––
 (E) = –––––––––––––

To express the mass fraction as a percentage, you need to multiply the right side of the formula by 100%

Independent work.

2.1. Underline the compound in which the largest mass fraction of sulfur is:

a) Na 2 SO 3 and Na 2 S 2 O 3; b) H 2 S and Na 2 S; c) Na 2 S 4 O 6 and Na 2 S 2 O 8.

2.2. Without doing any calculations, write the following compounds in a series in order of decreasing mass fraction:

a) hydrogen - H 2 O, H 2 O 2 _________________________

b) chlorine - Cl 2 O, Cl 2 O 7, ClO 2 ______________________

c) sulfur - SCl 4, S 2 Cl 2, SCl 2 ________________________

d) carbon - CH 4, C 2 H 2, C 2 H 4 ____________________

e) fluorine – P 2 F 4, PF 3, PF 5 _________________________

III. Lesson summary.

The results are summed up and the chemical concepts learned in this lesson are discussed: relative atomic and molecular masses, chemical formula, index, coefficient, mass fraction of a chemical element in a compound.

IV. Homework.

§5. ex. 1-5. (any of the students did not complete their independent assignments during the lesson, do them at home)

Irina Agarkova
Lesson on GEF. Chemistry. Mass fraction of a chemical element in a compound

Development lesson in accordance with the Federal State Educational Standard on the topic

SUBJECT LESSON Mass fraction of a chemical element in a compound.

Type lesson: lesson learning new material

Goals lesson:

Learn to calculate mass fraction of elements in the compound according to the formula of the compound and establish the chemical .

Basic concepts. Mass fraction of a chemical element.

Planned learning outcomes

Subject. Be able to count mass fraction of the element in the compound according to its formula and install chemical formula of a complex substance according to known mass fractions of chemical elements.

Metasubject. Develop the ability to establish analogies and use algorithms to solve educational and cognitive problems.

Main types of student activities. Calculate. Install chemical formula of a complex substance according to known mass fractions of chemical elements.

Educational: assimilation of new knowledge based on existing knowledge, independent search for new knowledge from various sources and consolidation of practical skills

Developmental: development of cognitive interest, independence of thinking, memory, initiative of students through the use of communicative-activity methods, a partial search approach and elements problem-based learning;

Educational: formation of communication skills, culture of communication, cooperation.

Methods: independent work of students.

Information and educational: ability to work with literature, take notes, choose the main thing, draw conclusions.

Communicative: conducting a discussion, the ability to prove your point of view.

Subject:. Calculate mass fraction of an element in a compound according to its formula. Install chemical formula of a complex substance according to known mass fractions of chemical elements

Equipment: textbooks, didactic cards for differentiated homework assignments.

Stage lesson Teacher activity Student activity

1. Org. moment

(Target : create motivation for learning activities)

Creating a problem situation

(Target: formation of system information analysis, development of skills to determine the goals and objectives of activities, choose means of achieving the goal) Mutual greetings, checking students’ readiness for lesson, equipment check. Preparing students to perceive new material.

Guys, let's say we have a substance - sulfuric acid H2SO4,

can we find out what atoms are included in the composition connections.

And their number?

And in which mass ratio they combine?

These substances are complex in composition.

2. Goal setting stage lesson(Target: developing in students the ability to independently set educational goals for lesson) -Name the topic of today lesson? Mass fraction of a chemical element in a compound

3. (mastering universal natural scientific methods activities: identifying cause-and-effect relationships) Guys, what do you think, can we calculate the share of each element in connection?

Today we will introduce you to a new concept.

W- mass fraction of the element in the compound.

n - number of atoms element.

Mr - relative molecular weight.

Students fill out a notebook with new concepts.

4. Stage "Discovery of new knowledge"

Learn the calculation algorithm mass fraction of the element in the compound.

Task No. 1

Working with the textbook. Learn the algorithm

Conclusion chemical formulas, if known mass fractions of chemical elements included in this substance

5. Initial check of mastery of new material Problem solving

Checking the task Students complete the task in their notebooks.

6 Secondary check of assimilation of new material. What new concepts did you learn today? lesson?

Student answers

7. Summing up. Reflection. ( Target: developing students’ ability to summarize lesson, generalize, draw conclusions, characterize your actions) - What new did you learn today

I realized that...

I learned …

I need... Students answer questions.

Flashcards – individually.

MBOU secondary school No. 139 of the Samara city district.

Chemistry lesson notes for grade 8.

Subject: Chemical formulas. Relative atomic and molecular masses. Mass fraction of an element in a compound.

Lesson Objectives

 educational:

— study the concepts: chemical formula, index, coefficient; writing and reading formulas.

- explore the differences between relative, atomic and molecular masses;

— will study the concept of the mass fraction of a chemical element and learn how to calculate it.

 developing:

— develop in students the ability to make simple, logical constructions based on chemical knowledge;

— develop the ability to use knowledge from various sections of school disciplines (physics, algebra) in non-standard research situations, and, if necessary, find missing information in reference and educational literature;

 educational:

— to cultivate personal reflection, that is, the ability to comprehend one’s actions and oneself in a problematic research situation;

— to foster self-organization and self-esteem in students when performing research tasks in class.

Equipment: tables “Relative atomic and molecular masses”, individual task cards for students, table by D.I. Mendeleev.

During the classes

I. Organizational moment

The teacher sets up the students to work during the lesson. Explains all stages of the lesson and students' actions at each of them.

— Guys, today each of you will become a researcher and will “gain new knowledge”: find out the composition of chemical formulas, the rules for writing and reading them; derive the formula for the mass fraction of a chemical element and calculate it.

II. Learning a new topic

1. The teacher's word.

— Each atom of any chemical element has its own mass, just like any physical body surrounding us, including you and me. But unlike us, the mass of atoms is very small. Therefore, scientists took the mass as a standard 1/12 the mass of a carbon atom 6 12 WITH(as the lightest) and the mass of the remaining atoms was compared with the mass of this standard, hence the name “Relative atomic mass” from the English. « relative » relative. This quantity has no units of measurement and is designated Ar . The numerical value of the relative atomic mass of any element is written in the periodic table by D.I. Mendeleev.

If a substance is formed by several elements (identical or different), then we are talking about molecules and “Molecular relative mass”. She folds up from atomic masses everyone chemical elements that form a molecule, multiplied by the number of these atoms. It also has no units of measurement and is designated Mr . For example:

Mr (O 2) = Ar (O) 2 = 16 2 = 32;

Mr (H 2 O) = Ar (H) 2 + Ar (O) = 1 2 +16 = 18;

Mr (H 2 SO 4) = Ar (H) 2 + Ar (S) + Ar (O) 4 = 1 2 + 32 + 16 4 = 98;

The teacher repeatedly reminds the students that the value of Ar is found in the periodic table of D.I. Mendeleev under the sign of a chemical element. The values ​​of the atomic masses of different chemical elements are added together. If there are several identical atoms in a molecule, their numerical value of atomic masses is multiplied by the number of these atoms. (a new topic will be reinforced when doing independent work in the research part of the lesson)

2. Research part(independent work of students under the guidance of a teacher), if difficulties arise for students, the teacher must be very careful and under no circumstances give students a direct correct answer, that is, they must obtain “ready-made knowledge” themselves. It is better to “push” the student to the correct decision with leading questions that stimulate mental activity, the need to connect existing knowledge from other areas with new material. This is necessary in order not to disrupt the students’ research process and to achieve the best results when learning new material, since knowledge acquired independently is retained in long-term memory than ready-made information.

Sample questions:

- How do you think?

- Imagine what will change if...?

— How will it change and what does it mean?

- Think about where else have you come across this concept? etc.

The teacher distributes task cards to the students, focusing their attention on the fact that this is an independent research work, but if necessary, you (the teacher) will definitely help and guide each student’s work in the right direction.

Cards - tasks

Subject: Chemical formula. Relative, atomic and molecular masses. Mass fraction of chemical elements.

Task 1. Chemical formula, its composition, writing and pronunciation.

A. Explore the qualitative and quantitative composition of chemical formulas. Analyze what each of them means in the formula.

Formula

High-quality composition
O 3	oxygen ( O)
H 2	hydrogen ( H)
Al 2 O 3	aluminum ( Al) and oxygen (O)

Conclusions:

1) High-quality composition chemical formula shows: _____________________________________ form a substance.

2) Quantitative composition chemical formula shows:

Form a substance.

IN. Analyze the entry and see what you think the index and coefficient in the chemical formula show.

2 Al 2 O 3

coefficient index

index – this is _____________, which shows the _______________ in a substance, written by the ______________________ symbol of a chemical element;

coefficient – this is _______________, which shows the amount of _____________ chemical substance, written by ______________ chemical formula;

IN. Explore the rules for reading formulas.

The order of pronunciation of the components of the formula:

1. coefficient

2. symbol of the chemical element * and its index (if any.)

3.next symbol of the chemical element and its index.

* When reading a chemical formula, the pronunciation of the symbol of the chemical element is read, not its name.

Independent work.

(consolidation of new material)

1.1. Write down the qualitative composition of each formula:

H 2 SO 4 _______________ FeSO 3 _____________________

H 3 PO 4 ________________ H 2 Cl 2 O 7 ____________________

1.2. Write down the quantitative composition of each formula:

O 3 __________________ K 2 O _______________________

Cl 2 __________________ MgCO 3 ____________________

MgO ________________ NaOH _____________________

H 2 SO 4 _______________ FeSO 3 _____________________

H 3 PO 4 ________________ H 2 Cl 2 O 7 ____________________

1.3. Read the formulas. Write down what you got:

Li 2 O ___________________________________________________

CaS ___________________________________________________

H 2 SiO 3 _________________________________________________

MgSO 4 _________________________________________________

Task 2. Dependence of the mass fraction of elements in a compound on some physical quantities.

Analyze on what parameters and how the mass fraction of an element in a compound depends.

A. Explore the composition and relative atomic masses of the elements of the hydrogen chloride molecule HCl.

Compound	qualitative	hydrogen H	chlorine Cl
	quantitative
Relative atomic mass of Ar

Compare the mass fractions of elements in the compound:  (H) _________  (Cl)

( ,  ,  )

B. Explore the composition of the molecules of ethane C 2 H 6 and acetylene C 2 H 2.

Compound

ethane C2H6	acetylene C2H2
Number of atoms carbon n(C)
Number of atoms hydrogen n(H)

Compare mass fractions hydrogen in ethane and acetylene:

 ( H) C 2 H 6 _______________  (H) C 2 H 2

( ,  ,  )

What parameter and how does it affect the value of the mass fraction of an element in a compound?

IN. Explore the composition of the molecule carbon dioxide CO 2 and carbon monoxide CO.

Compound

carbon dioxide CO 2	carbon monoxide CO
Number of carbon atoms n (C)
Relative molecular weight of the compound Mr

Compare the mass fractions of carbon in carbon dioxide and carbon monoxide:

 ( C) CO 2 _____________  (C) CO

( ,  ,  )

What parameter and how does it affect the value of the mass fraction of an element in a compound?

Summarize your conclusions and create a formula showing the dependence of the mass fraction on the parameters you found. For this: Write inversely proportional in the denominator

mass fraction value

 (E) = –––––––––––––

To express the mass fraction as a percentage, you need to multiply the right side of the formula by 100%

Independent work.

2.1. Underline the compound in which the largest mass fraction of sulfur is:

A ) Na 2 SO 3 and Na 2 S 2 O 3 ; b) H 2 S and Na 2 S; c) Na 2 S 4 O 6 and Na 2 S 2 O 8.

2.2. Without doing any calculations, write the following compounds in a series in order of decreasing mass fraction:

a) hydrogen - H 2 O, H 2 O 2 _________________________

b) chlorine - Cl 2 O, Cl 2 O 7, ClO 2 ______________________

c) sulfur - SCl 4, S 2 Cl 2, SCl 2 ________________________

d) carbon - CH 4, C 2 H 2, C 2 H 4 ____________________

e) fluorine – P 2 F 4 , PF 3 , PF 5 _________________________

III. Lesson summary.

The results are summed up and the chemical concepts learned in this lesson are discussed: relative atomic and molecular masses, chemical formula, index, coefficient, mass fraction of a chemical element in a compound.

IV. Homework.

§5. ex. 1-5. (any of the students did not complete their independent assignments during the lesson, do them at home)

Obernikhina Tatyana Sergeevna

chemistry teacher of the highest qualification categories.

Municipal educational institution "Secondary school No. 3 of Koryazhma"

Item . Chemistry.

Lesson topic Mass fraction of element.

8TH GRADE.

UMK G.E. Rudzitis.

Lesson type: Learning new material

Target : Develop the skill of solving problems on calculating the fraction and finding the mass of a solution component.

Tasks

Educational:

Form the concept of the mass fraction of an element;

To teach how to establish the simplest formula of a substance based on the mass fractions of elements.

Educational:

Develop skills logical thinking and interest among schoolchildren in chemical science.

Educational:

Develop a personality with an ecological way of thinking.

Foster a sense of camaraderie and responsibility in students.

Planned learning outcomes:

subject:

formation of systematized knowledge about the proportion of an element in a substance;

development of the ability to calculate the mass fraction of various substances;

meta-subject:

developing competence in the use of acquired knowledge in other academic disciplines;

personal:

formation of conviction in the necessity of chemical knowledge for human life;

Means of education :

Multimedia projector;

Computer;

Cards;

The flyleaf of the textbook with the table of D.I. Mendeleev;

Notebooks;

Table of D.I. Mendeleev;

Epigraph for the lesson:

Nature surrounds us with mysteries and, and

an attempt to solve them belongs to

to life's greatest joys.

W. Ramsay

Lesson steps

Lesson stage	Teacher activities	Student activities
1. Organizational moment.	Checks the children's readiness for the lesson. Greetings, positive attitude to the lesson.	Check readiness for the lesson.
2. Goal setting and motivation.	Creating a stimulating and motivating situation through a system of questions: Listed below are various minerals from which iron can be obtained (FeO, Fe2 O3 , Fe3 O4 ) (on a multimedia projector). Problem question: What mineral do you think is most beneficial to use to obtain iron?	They make their own assumptions about the question posed.
	Organizes the activities of students to formulate the topic and goals of the lesson. What do you think is the purpose of our lesson?	Determine the purpose of the lesson
	You have a certain amount of knowledge; what concepts learned earlier will help you achieve your goal?	Chemical element, chemical formula, relative atomic and molecular mass.
3.Updating and monitoring knowledge.	What can we say about these minerals?	Composed of iron and oxygen atoms
	Is it possible to answer the question posed by qualitative and quantitative composition?	Teamwork
		Molecular mass of substances
	Examination homework	On the given cards, students calculate the molar mass of iron oxides. After completing the task, they exchange cards with their deskmate and check together with the teacher.
3. Studying new educational material.	Organizes a conversation using presentation information, textbook text, and workbook. Controls the “discovery” of new knowledge. Corrects them. How can you graphically represent the written formulas? What is a share? Draws an analogy for calculating the fraction of a substance with mathematics. What is the main quantity in chemistry? What is the atomic mass of iron? How, based on knowledge of atomic and molecular mass, can one derive the formula of a substance? Calculate the mass fraction of iron in each substance and answer the question (return to the first slide) Discussion of completed tasks. Does the ore mining process affect the environment? Physical education minute. Let's remember the chemical elements. I tell you the name, if it matches the pronunciation, we raise our right hand, if not, we raise our left hand. Generalization and systematization Introduces new substances that contain the same chemical element. Calculate its mass fraction in each. SO2 and SO3 ω (S) = CO2 and CO ω (C) = ω (N) = НNO3 , НNO2 Complete tasks in workbook to secure the material.	Answer the proposed questions. Draw the composition of substances in different colors. Part of the whole. Students remember how the share is calculated in mathematics. Atomic mass element Derive the formula of the substance together with the teacher ω=(Аr·n/Мr)·100% They are counting on it. 3 students working at the blackboard Answer the question Make their own assumptions Physical education minute. One of the students, in the direction of the teacher, names the correct pronunciation. Make calculations They do the work.
4. Reflection and summing up the lesson.	Organizes reflection and summation of the lesson. If your mom asked you to text her about the most important thing in class, what would you write? Have we achieved our goals? Guys, finishing the lesson, please stick the given circle on one of the posters at the exit. (We have learned everything, we haven’t learned enough, serious improvement is required).	Pronounce their answers. They evaluate their work in posters at the exit.
5.Information about homework.	Offers a task in accordance with the capabilities: 1. Calculate which of the proposed compounds (hydrogen peroxide, water, sulfuric acid, calcium oxide, sodium peroxide - formulas written down by the teacher) has the largest mass fraction of oxygen? 2.Find the mass fraction of each element in the compound(Fe3 (P.O.4 ) 2 *8H2 O)	They select homework in accordance with their own capabilities and abilities, and their demonstrated interest in the topic being studied.

Literature used:

1. Chemistry, 8th grade, Inorganic chemistry, 8th grade, Rudzitis G.E., Feldman F.G., 2013.

2. Fadeev G.N. Tasks and tests for self-study in chemistry: a manual for students and teachers. - M.: BINOM. Knowledge Laboratory, 2008.

3. Workbook. 8th grade.

4. Didactic materials. 8-9 grades.