"Expressions of the Composition of Matter" The gas that sustains life - Oxygen PPT courseware 3

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"Expressions of the Composition of Matter" The gas that sustains life - Oxygen PPT courseware 3

Ask students to recall the following:

1. The meaning of element symbols:

represents an element

represents an atom

Sometimes it also means a substance

2. Three types of particles that make up matter:

Molecules: Most substances are made of molecules. For example, water is made up of water molecules, oxygen is made up of oxygen molecules, and hydrogen is made up of hydrogen molecules.

Atoms: All metals, rare gases, and some solid nonmetals. For example, iron is composed of iron atoms, copper is composed of copper atoms, helium is composed of helium atoms, and phosphorus is composed of phosphorus atoms.

Ions: There are also some substances made of ions. For example, sodium chloride (NaCl) is composed of Na + ions and Cl- ions

Question: How do we use universal formulas to express the composition of these substances in the world?

1. Use chemical formulas to express the composition of substances

1. Definition: A formula composed of element symbols and numbers.

For example: the chemical formula of water is H2O

The chemical formula of oxygen is O2

The chemical formula of iron is Fe

The chemical formula of sodium chloride is NaCl

Among them: the element symbol indicates the type of element contained in the substance and the number indicates the number of atoms.

Question: Comparing the chemical formula with the Chinese name, what do you think are the advantages of having a chemical formula?

2. The meaning of chemical formula expression

NaCl:

①Indicates a pure substance

②Indicates the type of elements contained in a pure substance

O2:

③Represents one molecule of the pure substance

④Indicates the composition of a molecule

Exam question training:

Express or tell the meaning of a symbol using a symbol:

3 potassium atoms______; 2 nitrogen molecules______; 5 nitrogen atoms______;

2 hydrogen atoms ______; 3 carbon dioxide molecules ______.

3H2O____________;

Mg____________________;

Al3+____________________.

Summary: The meaning of the numbers in the chemical formula (R)

(1) a represents the number of particles

(2) b represents the number of atoms.

(3) c means that an ion carries c units of positive (negative) charge

2. Writing of elemental chemical formulas

Represented by the corresponding element symbol

(1)Elements directly composed of atoms

1. Rare gases

Such as: helium (He), neon (Ne), etc.

2. All metals

Such as: magnesium (Mg), iron (Fe), etc.

3. Some solid non-metals

Such as: carbon (C), phosphorus (P), silicon (Si), etc.

(2)Elements composed of molecules

Write the number of atoms in the molecule in the lower right corner of the corresponding element symbol

Valence

1. The compound price is some numerical value, including positive and negative prices.

2. Some elements only show one valence, while some elements can show multiple valences.

3. Atomic groups also show valence.

4. How to express the valence of elements: H2O

5. The valency of elements in a single substance is 0.

6. The algebraic sum of positive and negative valences in a compound is 0.

1.Write chemical formula based on valence

Example 1 It is known that hydrogen has a valence of +1 and oxygen has a valence of -2. Write the chemical formula of this compound of water.

intersection method

1. Write the symbols of the elements in order, with positive valence on the left and negative valence on the right.

2. Mark the valence directly above the element symbol

3. Cross-write the absolute value of the valence to the lower right of the symbol of another element as its number of atoms.

2. Find the valency of elements based on chemical formulas

Principle: The sum of the positive and negative valence algebras in a compound is zero.

How to read chemical formulas (Textbook P91)

A compound composed of two elements: read from right to left as "a certain chemical"; sometimes it is also necessary to read the number of atoms of each element in the chemical formula.

KCl NH4Cl FeCl2 FeCl3 MgO HgS

Potassium chloride Ammonium chloride Ferrous chloride Ferric chloride Magnesium oxide Mercury sulfide

Al2O3 Fe2O3 Na2O MgCl2

Aluminum oxide Iron oxide Sodium oxide Magnesium chloride

CO2 CO SO2 Fe3O4 P2O5 MnO2

Carbon dioxide Carbon monoxide Sulfur dioxide Iron tetroxide Phosphorus pentoxide Manganese dioxide

Compounds containing atomic groups: Read the names of the atomic groups

Containing OH- ions is pronounced "hydroxide"

Example: NaOH reads sodium hydroxide

Containing NO3- ions read "nitric acid"

Example: NaNO3 sodium nitrate

Those containing SO42- ions are read as "sulfuric acid"

Example: CuSO4 copper sulfate

Those containing CO32- ions are read as "carbonic acid"

Example: CaCO3 calcium carbonate

Calculation based on chemical formula

1. Calculate the relative molecular mass of a substance based on its chemical formula

Relative molecular mass: the sum of the relative atomic masses of the atoms in the chemical formula

Exercise: Relative atomic masses: H-1, O-16, C-12, Ca-40, S-32, N-14, Cu-64

Relative molecular mass of CO2 = 12 + 16 x 2 = 44

Relative molecular mass of CaCO3 = 40+12+16x3=100

Relative molecular mass of H2SO4=1x2+32+16x4=98

Relative molecular mass of Cu(OH)2=64+2x(16+1)=98

Relative molecular mass of (NH4) 2SO4=2x(14+1x4)+32+16x4=132

Relative molecular mass of CuSO4 .5H2O=64+32+16x4+5x(1x2+16)=250

2. Calculate the mass ratio of the constituent elements of matter

The chemical formula clearly expresses the elemental composition of the substance and the atomic number ratio of the elements in the compound. Therefore, the mass ratio of the elements in the compound can be calculated through the chemical formula.

(2011 High School Entrance Examination) 5. (This question has 2 questions, totaling 12 points)

twenty four. (5 points) The media recently reported that some instant noodles on the market are contaminated by plasticizers. Long-term exposure to plasticizers can cause damage to the blood system and reproductive system. Among them, the molecular formula of plasticizer (DMP) is C10H10O4. beg:

(1) The relative molecular mass of DMP is _______;

(2) The mass ratio of the three elements C, H, and O in the DMP molecule is ____________;

(3) The mass fraction of oxygen element in DMP molecules is (the result is accurate to 0.01) ________.

[2012 High School Entrance Examination] 5. (This question has 2 questions, totaling 12 points)

twenty four. (5 points) In 2011, Chinese female scientist Tu Youyou discovered artemisinin (chemical formula of artemisinin: C15H22O5), which is a drug used to treat malaria and won the Lasker Award from the United States.

(1) Artemisinin molecules are composed of ______ elements.

(2) An artemisinin molecule contains ______ atoms.

(3) The mass ratio of the three elements C, H, and O in the artemisinin molecule is ____________.

power enhanced

1. The mass ratio of Fe2O3 and Fe3O4 containing the same mass of iron element is ( )

A, 3:2 B, 3:1 C, 30:29 D, 29:42

2. The ratio of the number of oxygen atoms contained in SO2 and SO3 molecules with equal masses is ( )

A, 1:1 B, 2:3 C, 5:6 D, 6:5

3. The mass ratio of SO2 and SO3 containing equal numbers of atoms is ( )

A, 3:4 B, 4:5 C, 15:16 D, 16:15

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"Expressions of the Composition of Matter" Life-Sustaining Gas - Oxygen PPT Courseware 2:

"Expression of the Composition of Matter" Oxygen, the life-sustaining gas PPT courseware 2 1. Chemical formula 1. Definition: A formula that expresses the composition of matter using a combination of element symbols and numbers. For example: the chemical formula of water is, the chemical formula of oxygen is, the chemical formula of carbon dioxide is ① Any substance...

"Expressions of the Composition of Matter" Life-Sustaining Gas - Oxygen PPT Courseware:

"Expression of the composition of matter" PPT courseware of oxygen, the life-sustaining gas. How to use formulas to express the composition of matter. Internationally, the formula that uses a combination of element symbols and numbers to express the composition of matter is called a chemical formula. Water: H2O Hydrogen peroxide: H2O2 Substances composed of molecules...

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Update Time: 2024-07-11

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