"Common Salt in Life" Salt Fertilizer PPT Courseware 5

"Common Salt in Life" Salt Fertilizer PPT Courseware 5

Knowledge review

Indicate which of the following substances are acids? Which are bases? Which are salts?

H2O CaCO3 HCl H2O2 Na2CO3

Ca(OH)2 MnO2 H2SO4 NaOH

Acid: HCl H2SO4

Base:NaOH Ca(OH)2

Salt:CaCO3 Na2CO3

Sodium chloride and human health

If you exercise too much or sweat too much, the Na+, Cl- and K+ in the body will be greatly reduced, which will affect the muscle and nerve responses, leading to nausea, vomiting, exhaustion and muscle spasms. Therefore, athletes need to drink specially prepared drinks before and after training or competition to replenish lost salt.

The practical value of table salt

Drinking a cup of salted water in the morning can cure constipation. Drinking salt water can cure sore throat and toothache.

If you accidentally eat poisonous substances, drink some salt water, which has a detoxifying effect. Gargling with light salt water every day can prevent various oral diseases.

When bathing, add a small amount of salt to the water to make your skin strong.

Tofu is perishable. If you dissolve salt in boiling water and soak the tofu after cooling, it can be stored for several months even in summer.

Peanut oil contains water and will smell bad if stored for a long time. You can stir-fry the salt, and after it cools down, add table salt at a ratio of 40 pounds of oil to 1 pound of salt. This will keep the peanut oil smooth in color and fragrant for 2 to 3 years.

Coarse salt purification

[Thinking 1] What is coarse salt? What impurities are contained in coarse salt?

Sodium chloride is widely distributed naturally, and a large amount of salt is contained in seawater, salt lakes, salt wells, and salt mines. By drying seawater or boiling salt well water, salt lake water, etc., people can evaporate and remove the water, and obtain sodium chloride crystals containing more impurities - coarse salt.

Coarse salt is processed and purified again to obtain refined salt.

Coarse salt contains more soluble impurities (such as MgCl2, CaCl2) and insoluble impurities (such as sediment, etc.)

Filter operation essentials

One stick: The filter paper is close to the inner wall of the funnel, and there should be no air bubbles in the middle, otherwise the filtration speed will be slow.

Two lows: ① The edge of the filter paper should be lower than the edge of the funnel; ② The liquid level in the funnel should be lower than the edge of the filter paper.

Three supports: ① When filtering, the glass rod should be placed against the side with three layers of filter paper to prevent the filter paper from being damaged and the filtrate becoming turbid;

②The mouth of the beaker containing the liquid to be filtered should be close to the glass rod;

③The lower end of the funnel should be close to the inner wall of the beaker to prevent droplets from splashing.

Also note: When filtering, it is best to filter the upper filtrate first, and then pour the solution mixed with a large amount of precipitate into the funnel to avoid the precipitate entering the funnel first and possibly clogging the filter paper, making the filtration speed too slow.

Result of discussion

1. Reasons why the filtrate is still turbid after filtration:

(1) The filter paper is damaged during filtration.

(2) When pouring liquid, the liquid level exceeds the edge of the filter paper.

2. Possible errors during the experiment (reasons for low yield):

(1) Too much coarse salt is added during dissolution and it is not completely dissolved, which reduces the yield of refined salt.

(2) Droplets splash out during dissolution and stirring, and the yield decreases.

(3) During filtration, the liquid spilled or the glass rod and beaker were not washed, resulting in the loss of NaCl, thus reducing the yield.

(4) Failure to stir in time during evaporation or stopping heating too late causes droplets to splash, thus reducing the yield.

What is evaporation? What should we pay attention to during evaporation operation?

Evaporation is generally a process in which the solvent is continuously volatilized by heating. The following aspects should be paid attention to during evaporation operation:

1. The evaporating dish should be placed on the iron ring. When stopping heating, do not place the evaporating dish directly on the experimental table immediately to avoid scalding the experimental table.

2. During the heating process, use a glass rod to stir continuously to prevent droplets from splashing due to excessive local temperature.

3. When a large amount of solid appears in the evaporating dish, stop heating and use the residual heat to evaporate the filtrate to dryness.

What role do glass rods play in the purification of coarse salt?

The effect of using glass rod three times

①Dissolution: Stir to accelerate dissolution

②Filtering: Drainage

③Evaporation: Stir to prevent local overheated droplets from splashing

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