Chapter 7 of Chemistry of the Third Year of Junior High School, Acids and Alkali Salts, and the Key

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Unit 07 Combustion and its utilization.

1. Burning and extinguishing fires.

1. Combustion conditions: (1) combustibles (2) oxygen (or air) (3) temperature reaches the ignition point (indispensable).

2. The principle of fire extinguishing: (as long as any one of the combustion conditions is eliminated).

1) Eliminate combustibles, (2) Isolate oxygen (or air), and (3) Cool down below the ignition point.

3. Factors affecting the combustion phenomenon: the nature of combustibles, the concentration of oxygen, and the contact area with oxygen.

There are two conditions for the fuel to be fully combusted: (1) there must be enough air; (2) The fuel has a large enough contact area with air.

4. **: Combustibles burn rapidly in a limited space, and the gas volume expands rapidly.

All mixtures of flammable gases, vapors of flammable liquids, and mixtures of combustible dust and air (or oxygen) can occur when exposed to fire**.

2. Fuel and energy.

1. Three major fossil fuels: coal, oil, and natural gas (mixtures, all non-renewable energy).

1) Coal: "industrial grain" (mainly carbon); Pollutants emitted by coal combustion: SO2, NO2 (causing acid rain), CO, soot, etc.

2) Oil: "the blood of industry" (mainly containing carbon and hydrogen); Pollutants in vehicle exhaust: CO, unburned hydrocarbons, nitrogen oxides, lead-containing compounds, and soot.

3) Natural gas is a gaseous fossil fuel (main component: methane) and is a cleaner energy source.

2. Two kinds of green energy: biogas and ethanol.

1) The main component of biogas: methane.

Chemical formula of methane: CH4 (the simplest organic, the organic with the smallest relative molecular mass).

Physical properties: colorless, odorless gas, less dense than air, extremely difficult to dissolve in water.

Chemical properties: flammable CH4+2O2 ignition CO2+2H2O (emits a blue flame).

2) Ethanol (commonly known as: alcohol, chemical formula: C2H5OH).

Chemical properties: flammable C2H5OH+3O2 ignition 2CO2+3H2O

Industrial alcohol often contains toxic methanol CH3OH, so it cannot be used to prepare wine!

Ethanol gasoline: advantages (1) saving petroleum resources (2) reducing automobile exhaust (3) promoting agricultural development (4) ethanol can be renewable.

3. Energy changes in chemical reactions.

Exothermic reactions: as in all combustion.

Endothermic reactions: reactions that are generally "high temperature".

4. New energy: hydrogen energy, solar energy, nuclear energy, wind energy, geothermal energy, tidal energy, hydrogen are the most ideal fuels

1) Advantages: abundant resources, more heat release, no pollution.

2) Problem-solving: How to produce hydrogen in large quantities and cheaply? How to safely transport and store hydrogen?

1. Combustion conditions and the principle of fire extinguishing; 2. Safety knowledge of flammable and explosive substances;

3 Coal, oil, and natural gas are the three major fossil fuels 4 Changes in energy in chemical change.

5 Environmental impacts of fossil fuel combustion; 6 The importance of using and developing clean fuels and various energy sources.

Difficulties: 1. Instruct students to investigate the fire situation;

2 Common fire extinguishing methods and scope of use.

3. Conditions and significance of sufficient fuel combustion;

4 Change in energy in chemical change.

5 "Simulation Experiment of Acid Rain Hazards"**;

6. Establish the awareness of cherishing resources, protecting the environment, and caring for the earth.

Junior 3 Chemistry Chapter 7 Review Renjiao Edition.

One. This week's teaching content:

Chapter 7 Review.

1.Solution.

The concept of solutes and solvents and the ability to distinguish between solutes and solvents.

The concept and basic characteristics of a solution.

The application of solutions in life and production.

2.Saturated and unsaturated solutions.

The concept of saturated and unsaturated solutions, and the ability to distinguish between concentrated and dilute solutions.

The mutual conversion of saturated and unsaturated solutions under certain conditions.

3.Solubility.

Factors that affect the solubility of a substance.

The concept of solubility and the calculation of related concepts.

4.Filtration and crystallization:

Operational considerations for filtering.

Crystallization, the concept of crystallization and the method of crystallization.

Evaporation crystallization. Cooling crystallization.

5.The mass fraction of the solute in solution.

Definition and calculation formula of the mass fraction of solute.

Calculation of the mass fraction of solutes.

Two. Key points, difficulties:

1.The concepts of solution, saturated solution, unsaturated solution.

2.The concept of solubility and the calculation of related concepts.

3.Basic operations for filtering.

4.Calculation of solute mass fraction in solution.

Teaching process] one. Solution concept: A solution is one or several substances that are dispersed into another substance to form a homogeneous and stable mixture, which is called a solution. Uniformity means uniformity, and stability means that there will be no precipitation and delamination after standing.

Two. The concept of saturated solution and unsaturated solution: at a certain temperature, in a certain amount of solvent, the solution that can no longer dissolve a certain solute is called the saturated solution of this solute; A solution that can also continue to dissolve a certain solute is called an unsaturated solution of this solute.

Three. The concept of solubility of a solid substance The mass dissolved by a solid substance when it reaches saturation in 100 grams of solvent at a certain temperature is called the solubility of the substance in this solvent. If the solvent is not specified, solubility is usually referred to as the solubility of the substance in water.

For example, the solubility of NaCl at 20 is 36 grams, which means that at 20, the solution reaches saturation when 36 grams of sodium chloride is dissolved in 100 grams of water. Or, at 20 o'clock, 100 grams of water can dissolve up to 36 grams of sodium chloride.

Four. The mass fraction of the solute in solution.

Usually the solution is thick and diluted, such as the sugar water is thick and sweet, but this way to distinguish the solution is still relatively rough, we must know exactly how much solute is in a certain amount of solution, that is, we must know the representation of the composition of the solution, and the junior high school stage mainly understands how to use the solute mass fraction to represent the composition of the solution.

NaohcaCO3==High temperature==CaO+CO2 gas is produced from CaCO3 H2O Na2CO3.

cao+h2o==ca（oh）2

Ca(OH)2+Na2CO3==CaCO3 precipitation+2NaOH from Cu H2O HCl, Please!

Copper is used as an anode for electrolysis of HCl solution.

Cu + 2HCl = energized = = CuCl2 + H2 gas.

NaohcaCO3 is prepared from CaCO3 H2O Na2CO3 == Heating ==CaO+CO2

cao+h2o==ca(oh)2

Ca(OH)2+Na2CO3===CaCO3+2NaOH is prepared from Cu H2O HCl, CuCl22Cu+O2==Heating==2CuO

cuo+2hcl==cucl2+h2o

CaCO3—High temperature—CO2+CAO

cao+h2o——ca（oh）2

Ca(OH)2+NaCO3——CaCO3 (precipitate)+2NaOHHCl is dissolved in H2O to form hydrochloric acid.

2Cu+O2—Heating—2Cuo

cuo+2hcl——cucl2+h2o

1. Definition of acid: hydrogen ion + acid ion.

Alkali: metal ion + hydroxide ion.

Salt: metal ion + acid ion.

2. Acid-base indicator.

Acid + litmus – turns red.

Acid + phenolphthalein - unchanged.

Alkali + litmus - turns blue.

Base + phenolphthalein - reddening.

3. Chemical properties.

Acid + Active Metal = Salt + Hydrogen.

Acid + Metal Oxide = Salt + Water.

Acid + alkali = salt + water.

Acid + salt = salt + acid.

Alkali + non-metallic oxide = salt + water.

Alkali + salt = salt + alkali.

Salt + Metal = Metal + Salt.

Salt + Salt = Salt + Salt.

4. Conditions for metathesis reaction.

One of the water, gas, and precipitation is generated.

5ph. 7 is acidic, = 7 is neutral, >7 is alkaline.

6. Solubility formulas, or common precipitation, should be memorized.

In simple terms, the framework is these, as well as the physical properties of common acids and bases and related equations.