We get the molar mass in moles. A mole is a unit of quantity of a substance. Molar mass. Using new formulas, we solve problems

Chemistry lesson in grade 8 on the topic “Amount of substance. Moth"

Lesson Objectives:

- to acquaint students with a new physical quantity - the amount of a substance, with its unit of measurement - a mole; learn to use the amount of matter and the mole.

Give the concept of molar mass, continue the formation of the concept of the amount of substance, the ability to use this value, enrich the content chemical formula.

Tasks:

To form during the lesson the concepts of "amount of substance", "Avogadro's number".

To form the ability to solve problems using the concepts of "amount of substance", "Avogadro number".

Continue to develop experimental skills in working with substances, the ability to observe, analyze, draw conclusions, highlight the necessary information.

Planned result:

Students know the concepts of "amount of substance", "Avogadro number", they can solve calculation problems using these concepts

Lesson type: combined ICT - a lesson using interactive teaching methods.

Lesson plan.

I stage. Organizing time

Greeting, creating a positive emotional mood.

Checking students for class.

Good afternoon guys!(mark missing)

I'm glad to see you. I see smart, kind faces in front of me. In order to understand how we will work today, I want to know what mood you are in. If you're in a good mood, smile at me. Look at each other, smile!

I am sure that today's lesson will bring us satisfaction and be fruitful, and your mood will not worsen by the end of the lesson.

II stage. Updating the necessary knowledge and skills, including verification homework(slide 2)

Where in the Periodic Table are the elements corresponding to simple substances metals?

Where are non-metals found in the Periodic Table?

What are the general physical properties metals?

What is allotropy?

Give examples of allotropy?

Complete the sentences: (slide 3)

Known 22 non-metal

Iodine crystals purple colors

liquid non-metal bromine

Carbon forms diamond and graphite

After a thunderstorm in the air is formed ozone

From the sentences below, write out the numbers corresponding to metals in one column, and the numbers corresponding to non-metals in another column. (slide 4)

1. Aggregate state: solid.

2. Have a metallic sheen.

3.Do not have a metallic sheen.

5. Electrically conductive.

6. Gaseous.

7. In the solid state - brittle.

8.Plastic.

9.Do not conduct heat.

Metals

1,2,4,5,8

non-metals

1,3, 6,7, 9

(slide 5) Assess your condition before a new topic.

III stage. Explanation of new material. (slide 6)

The glue spilled - the words stuck together. Separate the words from each other with dashes.

The teacher communicates the goals and objectives of the lesson.

Recording the topic of the lesson (slide 7)

The teacher reminds students that chemistry is the science of substances and their transformations. To obtain a certain amount of product (in chemical laboratory or at the factory) it is necessary to take strictly defined quantity initial substances.

Chemists, conducting experiments, noticed that the composition of the products of some reactions depends on the ratios in which the reactants were taken.

(slide 8) For example, if coal is burned in excess of oxygen, carbon dioxide is produced:

C + O 2 →CO 2

And if you take 2 times less, you get carbon monoxide:

C + 0.5O 2 → CO 2

In the first case, 1 oxygen molecule reacted with 1 carbon atom, and in the second case, one oxygen molecule reacted with two carbon atoms.

The question arises: how to measure a certain number of atoms or molecules?

It is easy to measure the mass of a substance (with the help of scales) or the volume of a gas or liquid (with the help of measuring utensils). So you need physical quantity, which allows you to convert the number of atoms or molecules into mass or volume.

Let's carry out simple calculations: the mass of the lightest atom - hydrogen is 1.66 10 -24 g, this mass is taken as a unit of relative atomic mass: Ar(H) = 1. Now suppose we have 1 g of hydrogen atoms. How many atoms will there be in this mass? To calculate, you need to divide the mass of a portion of hydrogen by the mass of 1 hydrogen atom: 1 g: 1.66 11 -24 g ≈ 6.02 10 23 atoms.

In the mass (in grams) of any element, numerically equal to the relative atomic mass, will contain the same number of atoms of this element.

The mass (in grams) of any substance, numerically equal to its relative molecular weight, will contain the same number of molecules. This is a constant value, it is called Avogadro's number, denoted by N A .

(slide 9)

(slide 10)What associations does the drawing evoke? (mol). The unit for measuring the amount of a substance was called " mole"

The amount of a substance containing 6.02 10 23 structural units of a substance is called molem .(slide 11)

Based on the examples considered, the teacher adds that the number of other particles is also measured in moles: atoms, ions, electrons, etc.

(slide 12/1)1 mole of any substance in any state of aggregation contains N A = 6∙10 23 its molecules.

mole - unit amount of substance .

The amount of a substance is a physical quantity introduced to link the number of structural units of a substance and its mass or volume.

(slide 12/2) The amount of a substance is denoted n(en) or  (nu) (obsolete), measured in moles.

n[mol]

(slide 13)General slide of the amount of substance.

(slide 14-15) 1 mol of any substance has a mass numerically equal to the relative molecular mass, but having a unit of g / mol

This mass is called molar , denoted by M.

Mr = M [g/mol]

How can you see 1 mole of a substance?

Take a tablespoon, fill it with water and pour it into a beaker. This will be approximately 1 mole of water. Pour another spoonful of water into a glass. Now there are 2 moles of this substance in the glass. Let's add one more spoon. The amount of water will become equal to 3 mol.

(slide 16)Demonstrate to the class some substances the amount of 1 mol: 56 g of iron powder ( Fe ), 58 g salt ( NaCl ), 342 g sugar ( C 12 H 22 O 11 )