"Chemical Equations" Chemical Changes and Their Representation PPT Courseware 2

Description

"Chemical Equations" Chemical Changes and Their Representation PPT Courseware 2

1. Law of conservation of mass

The sum of the masses of all substances participating in a chemical reaction is equal to the sum of the masses of all substances produced after the reaction.

2. Reasons why chemical reactions follow the law of conservation of mass

Type of element Type of atom

Element mass Number of atoms

Total mass of substance Atomic mass

Types of matter Types of molecules

The number of molecules may vary

3. There are two principles to follow when writing chemical equations:

Must be based on objective facts

Must obey the law of conservation of mass

4. Steps to write chemical equations

(1) Based on the experimental facts, write the chemical formulas of the reactants and products on both sides of the formula, and draw a short line between the two sides.

(2) Balance the chemical equation and change the short line into an equal sign

(3) Mark the conditions for the chemical reaction to occur, and change the dashes to equal signs.

Common chemical equations

1. Combination reaction

ignite

(1) 2Mg+O2===2MgO

ignite

(2)S+O2 ====SO2

ignite

(3) C+O2====CO2

ignite

(4) 2C+O2====2CO

high temperature

(5)CO2+C====2CO

ignite

(6)4P+5O2====2P2O5

2. Decomposition reaction

MnO2

2KClO3=====2KCl+3O2↑

2KMnO4===K2MnO4+MnO2+O2↑

MnO2

2H2O2====2H2O+O2↑

power ups

2H2O====2H2↑+O2↑

H2CO3===H2O+CO2↑

5. The meaning of chemical equations (information provided)

a. What substances participate in the reaction (reactants)

b. What substances (products) are generated?

c.Reaction conditions

d. Particle number ratio between reactants and products

e. Mass ratio between reactants and products

9. Calculation steps based on chemical equations

1. Set up the unknown quantity (set up whatever you are asking for, and set up the problem you are asking for at once)

2. Write chemical equations and balance them (chemical equations used in calculations)

3. Write the relative molecular mass, known quantities, and unknown quantities of the relevant substances (only write the substances related to the known and sought, write the relative molecular mass at the top, the mass of the substance at the bottom, and the known units)

4. List proportional formulas and solve them (list direct proportional formulas, the same amount above and below, the same substance on the left and right)

5. Write the answer concisely

Classroom ability training

1. There must be no change before and after the chemical reaction ( )

Number of atoms ② Number of molecules ③ Type of elements ④ Total mass of all substances participating in chemical reactions

⑤Types of matter ⑥Types of atoms

A.①④⑥ B． ①③⑤ C. ①③④⑥ D. ①③④⑤⑥

2. The law of conservation of mass reveals ( ) in chemical reactions

A. Reaction conditions B. Which substances react

C. Which substances are products D. The mass relationship between reactants and products

3. Which of the following statements conforms to the law of conservation of mass ( )

A. Water is heated and turns into water vapor. After the change, the mass is equal.

B.50mL water mixed with 50ml alcohol is not equal to 100mL

C. Contains 10g hydrogen and 80g oxygen in 90g water

D. 1g of sulfur combines with 1g of oxygen to form 2g of sulfur dioxide.

summary

1. Calculations based on chemical equations are based on:

Basis: direct proportional relationship

2. The computational steps for calculating chemical equations are:

①Assume (unknown quantity)

② Square (equation)

③ Off (known or unknown relative molecular mass of related substances)

④Solving ratio (column proportional formula)

⑤Answer (concise answer)

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Update Time: 2024-11-22

This template belongs to Chemistry courseware Hunan Education Edition Ninth Grade Chemistry Volume 1 industry PPT template

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