"Chemical Equations" PPT

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"Chemical Equations" PPT

Part One: Review

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.

element symbol

1. What is an element symbol?

Symbols used internationally to represent various elements.

2.The meaning of element symbols

(1) Represents an element (macro).

(2) Represents 1 atom of this element (microscopic).

(3) Substances directly composed of atoms can also represent such substances (macroscopic).

Chemical equation PPT, part 2 content: chemical formula

1. Chemical formula definition

Use element symbols to represent the composition of matter.

2.The meaning of chemical formula

(1) Represents a substance

(2) Indicates the elemental composition of the substance

(3) Represents a molecule of the substance

(4) Indicates the molecular composition of the substance

(5) Indicates the relative molecular mass of the substance

A chemical formula can be used to represent a certain substance. So, can a chemical formula be used to represent a chemical reaction?

Chemical Equation PPT, Part 3: Definition of Chemical Equation

A chemical formula that represents a chemical reaction is called a chemical equation

chemical equation writing

1. Writing principles

A. Based on objective facts; (reactions are real and cannot be made up out of thin air)

B. Comply with the law of conservation of mass. (The number of atoms of each element before and after the reaction must be equal)

2. Writing steps

(1) Write the correct chemical formulas of the reactants and products.

Based on the reaction facts, write the chemical formula of the reactants on the left side of the formula and the chemical formula of the product on the right side, with a dash in the middle.

If there is more than one reactant or product, connect them with a "+" sign (do not read "add", read "follow" and "and") respectively.

Take hydrogen peroxide to produce oxygen as an example:

(2) Balance chemical equations.

Why balance chemical equations?

Because chemical reactions must follow the law of conservation of mass.

How to balance a chemical equation?

The number of atoms of each element on the left and right sides of the formula must be equal.

(The equal sign is not read as "equal", but read as "generated")

(3) Indicate the reaction conditions and the status of the products.

If the reaction requires ignition, heating (use △), high temperature, electricity, catalyst, etc., the conditions must be written above or below the equal sign.

If there is no gas in the reactants but gas is produced in the product, it is represented by "↑" next to the chemical formula of the gas.

If the reaction occurs in a solution, there is no solid in the reactants, but there is a solid in the product, then it is represented by "↓" next to the chemical formula of the solid;

Chemical Equation PPT, Part 4: The Meaning of Chemical Equations

Reaction conditions

1. Indicate the conditions under which the reaction takes place.

Macroscopic significance

2. Indicates what substances participate in the reaction and what substances are produced as a result.

microscopic meaning

3. Indicates the number ratio of particles among various substances. (atoms and molecules)

Quantitative meaning

4. Indicates the mass ratio between reactants and products.

Chemical Equations PPT, Part 5: Practice

1. Write the chemical equation for the following reaction:

(1) Copper burns in air to form copper oxide (CuO)

(2) Iron oxidizes in the air to form iron oxide (Fe2O3)

2. The meaning of chemical equations

(for example)

(1), indicate that the reactants are ______ and the products are ______.

(2), indicating that the conditions for the reaction are ______;

(3), indicating that the ratio of the number of molecules between each substance is ______;

(4) Indicate that the mass ratio of reactants and products is ______;

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Update Time: 2024-11-20

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