Tell me a little bit about Thermal Phenomena in Chemical Reactions .

Some of the chemical reactions we have learned are for the preparation of the required substances, such as the preparation of oxygen in the laboratory, the preparation of CO2 and H2, etc., and some chemical reactions are for the use of the heat released in the reaction. For example, the combustion of charcoal and methane CO2

The energy released in the chemical reaction of CH4 2O2 CO2 2H2O is the most important energy source in the world today, such as: coal, oil, natural gas and other fossil fuels generated by combustion. Refer to Figure 1 14 on page 19 of the textbook Schematic diagram of the composition of fossil fuel and hydropower energy consumption in China in 1990.

Therefore, it is very important to study chemical reactions and their energy changes. Topic "Section 3 Energy Changes in Chemical Reactions" was introduced

1. Energy changes in chemical reactions.

Demonstration Experiment 1 3] Al reacts with dilute hydrochloric acid.

Note: Specifications for the use of the dropper.

Experimental Phenomenon: A large number of bubbles are generated. Touch the wall of the test tube with your hands, and the temperature of the solution rises. Analysis.

Conclusion: Al tablets react with dilute hydrochloric acid to form gas and release heat at the same time.

Demonstration Experiment 1 4] In a small beaker, add about 20 g of [Ba(OH)2 8H2O] that has been ground into powder and place the small beaker on a slide that has been pre-dripped with 3 4 drops of water. Then about 10gnH4Cl crystals were added, and the glass rod was quickly stirred to make Ba(OH)2 8H2O fully react with NH4Cl.

Phenomenon: The glass pieces stick to the beaker. The reaction of Ba(OH)2 8H2O with NH4Cl was analyzed to absorb heat.

The chemical reactions that have been exposed to are accompanied by changes in energy, usually in the form of changes in heat. There are some chemical reactions that release heat, and some chemical reactions that absorb heat.

Exothermic reaction: A reaction with heat is called an exothermic reaction. For example: AL flakes react with dilute hydrochloric acid, coal and natural gas that we burn for heating in winter, and so on.

Endothermic reaction: The reaction that absorbs heat is called an endothermic reaction.

c＋h2o(g)＝co＋h2－q c＋co2＝2co－q

Why is there often a change in energy in a chemical reaction? There is the separation and bonding of atoms in chemical reactions.

Assign students to read the first paragraph on page 20 of the textbook and read Figure 1 17.

Summary: The process of chemical reaction can be regarded as the "release" of energy "stored" in matter into heat energy (light energy, electrical energy), etc.; Or the process by which heat energy is converted into energy inside a substance and "stored".

Narrator: It is important to study the thermal phenomena in chemical reactions The energy released by chemical reactions is one of the most important energy sources in the world today. The properties of matter and the law of change of chemical reactions are studied through the change of energy.

When a chemical reaction occurs, it is accompanied by the release or absorption of heat. If the energy to break the bond of the reactant is less than the energy required to form the product, then the reaction is exothermic. Otherwise, it is an endothermic reaction.

I don't know if you have a division of arts and sciences. If you score, you will learn it in the third year of high school. It won't be hard, don't worry.

1. The heat of reaction is called the heat of reaction, that is, after the chemical change of the system, the temperature of the reaction product returns to the temperature of the initial state before the reaction, and the heat released or absorbed by the system. There are usually two types of heat of chemical reaction: constant volume heat of reaction and constant pressure heat of reaction.

2. In principle, the heat of reaction can be measured by two experimental methods: (1) direct measurement with a calorimeter, for example, the reaction is carried out in a closed container with adiabatic disadvantages, and the heat of reaction can be calculated by energy balance; (2) The reaction equilibrium constant at different temperatures is determined first, and then the thermodynamic formula of correlation reaction heat, reaction equilibrium constant and temperature is used to calculate the heat of reaction. For chemical reactions where it is difficult to control and determine the heat of reaction or equilibrium constant, Gaisce's law proposed by 1840 (the thermal effect of a chemical reaction or physical change is independent of its pathway) can be used.

Calculated indirectly using the heat of formation (the change in enthalpy when 1 mol of a compound is synthesized from the most stable elementalization at a constant temperature) or the heat of combustion (the change in enthalpy of 1 mol when a substance is completely combusted).

I don't know how specific I want to be, so I'll write a little briefly.

Thermochemistry 1Collision theory.

2.The relationship between enthalpy (h) and heat of reaction (q), entropy (s) and free energy (g) δg = δh-tδs

3.Thermochemical equations and Gaisce's law.

Standard state (note the unit of δh and its positive and negative markings, the change of the coefficient of the equation and the same multiple of δh, and the effect of the change of the state of matter on δh.)

The content and application of Geisce's law (equations and addition and subtraction of enthalpy changes)4The principle and application of Le Chatre (combined with thermochemical equations and chemical equilibrium), the heat of reaction and the conversion rate ......

5.Chemical reaction rate (influencing factor: internal ......, external ......) and chemical equilibrium (often used as an image problem).

Since there is no reference to the book, please understand that there is any omission

Junior Chemistry - Endothermic and Exothermic phenomena during dissolution.

The white phosphorus of d1mol and the red phosphorus of 4mol have the same mass as the title, and the energy of red phosphorus is lower than that of white phosphorus at the same mass, only b d Since the energy of red phosphorus is lower than that of white phosphorus, then red phosphorus needs to absorb heat when it is converted into white phosphorus, so d is chosen

aThe heat of combustion is 1mol of the heat when the reactant is completely reacted, hydrogen should be 1mol, and water should be liquid.

The lower the energy of b, the more stable it is, and the heat absorption from graphite to diamond indicates that graphite has less energy by itself, so graphite is more stable.

As long as you have a certain reactive formula, h cannot be changed.

d c(s)+1 2o2(g)=co(g) h2co(g)+1 2o2(g)=co2(g) the addition of the two equations on h3 c(s)+o2(g)=co2(g); H1 is equivalent to a step-by-step reaction.

h3 +△h2=△h1

Originally, 1 should be numerically greater than 2, but since they are both exothermic reactions, h<0, h1 < h2

Last pick D