"Crystal Phenomenon" Solution PPT Courseware

"Crystal Phenomenon" Solution PPT Courseware

Preview of new knowledge

1. Crystals and crystallization

1. Crystal: Crystals generally have ___________ and have melting and boiling points of ______.

2. Crystallization: The process of forming crystals. Crystals can be formed from ______ solution, and the solution after the crystals are separated is _______ solution.

3. Two common methods for precipitating crystals from solutions

Cooling crystallization method (i.e. cooling thermally saturated solution) - generally suitable for solutes whose solubility changes with temperature ________.

Evaporative solvent crystallization method (i.e. constant temperature evaporation of solvent) - generally suitable for solutes whose solubility changes ___________ due to the influence of temperature.

2. Purification of coarse salt

1. step:___________________.

2. Purpose: To remove ________ impurities from coarse salt.

3. Glass rods are used in all three steps. The functions of the glass rods are ___________, _______ (that is, the liquid _________ flows into the funnel), and ____________________.

Three filtering operations

1. Filter composition: funnel and filter paper.

2. The instruments used in filtration operations are ________, beaker, _______, and funnel.

3. The role of the glass rod in the filtration operation: ___________, allowing the liquid to flow into the filter along the glass rod.

4． Operating instructions: _______________. That is: the first finger is ______ tightly attached to the inner wall of the funnel; the second low finger is _________ lower than the edge of the funnel and _________ the edge of the filter paper; the third finger is _________ close to the middle of the inclined glass rod, and the third finger is _________ On one side of the filter paper, _____________ is close to the inner wall of the liquid-contact beaker.

Interactive exploration

Explore point 1: Crystallization method

[Scenario display]Salt in the summer and alkaline in the winter.

[Question Research]What methods can we use to crystallize a solute from a solution? Why "salt in the summer and alkali in the winter"?

[Inductive improvement] Substances whose solubility is greatly affected by temperature adopt cooling crystallization method (i.e. cooling crystallization), and substances whose solubility is not greatly affected by temperature adopt evaporation solvent crystallization method. The solubility of sodium chloride is not greatly affected by temperature, but the solubility of soda ash (sodium carbonate) is greatly affected by temperature, so "salt is exposed to the sun in summer and alkali is harvested in winter."

[Application Example]

Example 1: Choose the appropriate method from the following methods to separate the following mixtures. (fill in the blank with serial number)

A． evaporative solvent crystallization method

B． cooling crystallization method

C. Dissolution and filtration method

(1) Extracting salt from sea water: ________.

(2) Separate MnO2 from the residue of O2 produced in the laboratory: ________.

(3) Separate KNO3 from KNO3 solution containing a small amount of NaCl: ________.

[Method Instructions] To separate a mixture of soluble substances and insoluble substances, operations such as dissolution, filtration, evaporation and crystallization are required; crystallization methods are often used to separate two soluble mixtures. If the main substance is a substance whose solubility is greatly affected by temperature, the cooling crystallization method (also called cooling crystallization method) is generally used; if the main substance is a substance whose solubility is less affected by temperature, the evaporation solvent crystallization method is generally used.

Research point 2: Purification of coarse salt

[Scenario Demonstration]Removal of insoluble impurities in coarse salt:

[Question Exploration]What should we pay attention to when filtering? What are the possible reasons why the filtrate is still turbid after filtration? What is the role of glass rods in the purification of coarse salt?

[Integrated improvement]When filtering, you should pay attention to the operation essentials: "one stick, two low, three rely". It should also be noted that before filtering, the liquid to be filtered should be allowed to stand for a while, and then filtered after the upper layer is clarified, so as not to affect the filtration rate; when filtering, do not use a glass rod to stir in the filter to avoid breaking the filter paper. After filtration, the filtrate is still turbid. Possible reasons for failure: the beaker that receives the filtrate is not clean, the liquid level is higher than the edge of the filter paper when pouring the liquid, the filter paper is damaged, etc. The glass rod is used for stirring during the dissolution process to accelerate dissolution; for drainage during the filtration process; for stirring during the evaporation process to heat the liquid evenly and prevent droplets from splashing; after evaporation is completed, it is also used for for transferring solids.

[Application Example]

Example 2 Figure 7-4-1 is a diagram of a student’s experimental device for filtering.

(1) Write the name of the instrument marked with letters in the picture.

a___________, b__________.

(2) Point out two errors in the picture:

①_______________________________;

②_______________________________.

(3) Filtration is a method of removing ________ mixed in a liquid.

(4) After the student corrected his mistake, he filtered a glass of turbid water. After two filtrations, he found that the filtrate was still turbid. Please help him analyze the reason: ____________________ (just write two points).

On-site testing

Knowledge point 1: Crystallization method

1. A saturated solution of a solid substance. After evaporating the solvent or cooling the hot saturated solution to precipitate the crystals, the remaining solution is ()

A． Concentrated solution B. dilute solution

C. Unsaturated solution D. saturated solution

Knowledge point 2: Purification of coarse salt

2. Figure 7-4-2 is part of the operation of the crude salt purification experiment. The wrong operation is ()

Knowledge point 3: Filtering operation

3. Which of the following steps in the filtering operation is incorrect ()

A． Take a piece of round filter paper, fold it in half twice, open it into a cone shape, and put it into the funnel

B． If the filter paper is higher than the edge of the funnel, use scissors to cut off the excess so that the edge of the filter paper is slightly lower than the funnel mouth.

C. Wet the filter paper with a small amount of water so that the filter paper is close to the funnel and no air bubbles are left between the filter paper layer and the funnel wall.

D． Gently stir the liquid in the funnel with a glass rod to speed up filtration

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"Crystal Phenomenon" Solution PPT Courseware 2:

"Crystal Phenomenon" Solution PPT Courseware 2 Learning Objectives 1. Understand crystals and crystallization, and have a preliminary understanding of crystallization phenomena; 2. Master experimental methods for removing insoluble impurities in coarse salt. 1. Crystals and Crystallization How can such beautiful crystals be produced? Experiment 7-9: Alum..