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1.1化学反应与能量的变化（1.1 chemical reactions and changes in energy）
Chapter 1 chemical reactions and energies
Section 1 chemical reactions and changes in energy
Classical case
The following figure is a hot lunch box structure sketch, this kind of lunch box is convenient to carry, can be eaten with the use, it is very convenient to use. It is often used in outdoor outings. From the bottom of the cardboard table, a few minutes later, due to the catalytic effect of iron powder, magnesium powder easily reacted with water,
A lot of heat is released and the heat is supplied to make the food hot and people can eat.
Structure of instant lunch box
Problems and discussion:
1. why join the iron powder? What is the role of iron powder in this reaction?
2., in fact, the process constitutes a primary cell. The cathode and anode of the primary cell are analyzed and the electrode reaction equation occurring on each electrode is written.
3. iron powder can also use what material instead? Write out several alternative substances and summarize the properties of the alternative.
In fact, the principle that the medical instant heating rod (used for heating liquid medicine at a drip point) is similar to the structure and principle of the lunch box. Usually made of iron powder, carbon powder and water, it is insulated from air before use. If used, the outer layer of plastic film can be torn, and then wrapped around the bottle on the transfusion tube, can play the role of liquid heating.
Difficulty and essence
Exothermic reaction and endothermic reaction
Whether the reaction is endothermic or exothermic depends on the relative size of the total energy of the reactants and the products.
[1] the following statement is correct ()
The reaction that A. needs to heat up must be endothermic
B. exothermic reactions must occur very easily at room temperature
Whether the C. reaction is exothermic or endothermic depends on the relative size of the total energy of the reactant and the product
D. endothermic r
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