Give examples of separating or purifying substances in life and talk about their basic principles.

The separation and purification of substances, using the differences between the purified substances and impurities in some properties, adopt appropriate separation methods to remove impurities and obtain pure substances. Because in the process of purifying substances, besides suitable impurity removal reagents, it is often necessary to choose suitable separation methods, so the separation and purification of substances are interrelated.

1, physical methods for impurity removal and purification mainly include:

(1) filtration method (depending on the solubility of the substance). For example, sodium chloride solids in calcium carbonate solids can be removed, the mixture is dissolved in water, and then filtered, and the obtained solids are washed and dried to obtain calcium carbonate solids.

(2) crystallization method (depending on whether the solubility of a substance is affected by temperature changes). For example, in order to purify potassium nitrate from a mixture of potassium nitrate and sodium chloride, the mixture can be dissolved in hot water to prepare a hot saturated solution, then cooled and crystallized, filtered and dried to obtain a potassium nitrate solid.

2. Chemical methods mainly include:

(1) substitution method. If zinc powder in copper powder is removed, excessive dilute sulfuric acid or copper sulfate solution can be added to the mixture, and after full reaction, pure copper powder can be obtained by filtering, washing and drying.

(2) heating method. If calcium carbonate in calcium oxide is to be removed, it can be directly heated and calcined, and pure calcium oxide can be obtained after full reaction.

(3) precipitation conversion method. If copper sulfate in sodium sulfate solution is to be removed, sodium hydroxide solution can be added dropwise to the mixed solution until blue precipitate no longer occurs, and the dropwise addition can be stopped. The obtained mixture is filtered, and the filtrate is sodium sulfate solution.

(4) Gas conversion method. If sodium carbonate in sodium chloride solution is to be removed, hydrochloric acid solution can be dripped into the mixed solution until bubbles are no longer generated, and the obtained solution is sodium chloride solution.

(5) neutralization. If sodium hydroxide in sodium chloride is to be removed, an appropriate amount of hydrochloric acid solution can be dripped into the mixed solution to obtain a sodium chloride solution.

(6) gas washing method. If carbon monoxide is purified from the mixed gas of carbon monoxide and carbon dioxide, the mixed gas can be first introduced into concentrated sodium hydroxide solution and then into concentrated sulfuric acid to obtain pure carbon monoxide.

Extended data:

When purifying substances, we should first consider physical methods, and then consider chemical methods. And master the following four principles:

1, "turning waste into treasure"-try to choose a reagent that can transform impurities into required substances;

2. No new impurities can be introduced;

3. The added impurity removal reagent cannot remove the required substances;

4. The impurity removal reagent should be added in an appropriate amount or in excess, or in excess, which should be removed in the subsequent operation.