"Law of Conservation of Mass" Chemical Equations PPT Courseware 5

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"Law of Conservation of Mass" Chemical Equations PPT Courseware 5

think?

When a substance undergoes a chemical change and forms a new substance, what is the relationship between the sum of the masses of the reactants and the sum of the masses of the products?

propose a hypothesis

(1) The sum of the masses of the substances participating in the reaction is greater than the sum of the masses of the substances produced.

(2) The sum of the masses of the substances participating in the reaction is equal to the sum of the masses of the substances produced.

(3) The sum of the masses of the substances participating in the reaction is less than the sum of the masses of the substances produced.

1. Law of conservation of mass:

1. Explore the mass relationship between reactants and products in chemical reactions:

【Activity Research】

Exploration 1. White phosphorus combustion

Exploration 2. Reaction of iron nails and copper sulfate solution

Pay attention to observe:

(1) The state and change phenomena of reactants and products;

(2) Changes in quality.

Thoughts and Discussions

1. Are the results of the above two experiments the same as the predictions before the experiment? Why are there such experimental results? What if it is done in a closed container?

2. If a cover is placed over the burning magnesium bar and all the products are collected and weighed, what will be the experimental results?

Conservation of mass

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

1. Each substance refers to: all reactants and all products

2. "Sum" means: including the reactants and products in various states (gas, liquid, solid). Gases invisible to the naked eye should also be considered

3. "Participate" means: the mass of the excess remaining part of the reactants should not be counted

4. The law of conservation of mass only applies to chemical changes

3. Microscopic explanation of the law of conservation of mass:

The essence of chemical reactions is the process of recombination of atoms, that is, in all chemical reactions, the type of atoms does not change, the number of atoms does not increase or decrease, and the mass of the atoms does not change. Therefore, the sum of the masses of each substance before and after the reaction must be equal.

4. Application

The idiom "turning stone into gold" originally means a spell used by ancient sorcerers, which can turn stones into gold; now it is a metaphor for turning decay into magic. Some people say that he can turn limestone into gold. Please use your chemical knowledge to explain why limestone cannot turn into gold.

Answer: The types of elements remain unchanged during chemical reactions. The main component of limestone is calcium carbonate, which is composed of calcium, carbon and oxygen. Gold is made of the element gold, so it is impossible for limestone to turn into gold.

Class exercises:

1. Which of the following particles may change before and after a chemical reaction ( )

A. Type of atom B. Number of molecules

C. Number of atoms D. Atomic mass

2. The sum of the masses of each substance participating in the reaction is equal to the sum of the masses of each substance produced after the reaction. Because of( )

A. There is no change in the type of substance after the reaction

B． There is no change in the type of molecules after the reaction

C. The type, number and mass of atoms do not change after the reaction

D． There is no change in the type, number and mass of molecules after the reaction

3. According to the law of conservation of mass, it can be inferred that after iron wire is burned in oxygen, the mass of the product ( )

A must be equal to the mass of the wire B must be less than the mass of the wire

C must be greater than the mass of the wire D. The mass cannot be determined

Let’s compete to see who is the strongest!

1. In the chemical reaction A + B = C + D, 7gA and 9gB react completely, and the mass of C produced is exactly 3 times the mass of D. Then the mass of D produced is ____.

2. In the chemical reaction A+B2=AB2, the mass relationship between A and B2 is as shown in the figure. If 5gA and 8gB2 are fully reacted, the mass of AB2 produced is ( )

A.10g B.13g

C.16g D.18g

3． The four substances A.B.C.D undergo a chemical reaction under certain conditions. After a period of time, the relevant data are measured as follows:

Answer the following questions:

(1)The mass of D after the reaction is __g

(2) Substance C may be __________ (fill in the reactant, product, catalyst)

(3) The reaction type that occurs in the container is __________ (fill in the basic reaction type)

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Update Time: 2024-11-19

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