There are soft and hard waters, but how do you explain that?

1.Hard water Natural water containing calcium salts and magnesium salts. In general, groundwater such as well water and spring water has a large salt content, and surface water such as river water and lake water has a small salt content.

In hard water, calcium, magnesium can be present in the form of carbonates, bicarbonates, sulfates, chlorides, and nitrates. When calcium and magnesium in hard water mainly exist in the form of bicarbonate, such as Ca(HCO3)2, Mg(HCO3)2, it is called temporary hard water, when this hard water is heated and boiled, bicarbonate will decompose into carbonate and precipitate to remove If calcium and magnesium in hard water mainly exist in the form of sulfate, nitrate and chloride, it is called permanent hard water, and they cannot be removed by boiling.

The calcium and magnesium salts in hard water can interact with soap (sodium stearate) to form insoluble stearate, reducing the decontamination ability of soap. If hard water is used in the boiler, calcium and magnesium salts will form scale on the inner wall of the boiler when heated. Reducing the thermal conductivity of the boiler, increasing energy consumption, and even shortening the life of the boiler, sometimes clogging the pipes.

Therefore, boiler water must be softened (see).

The salt content in hard water is usually expressed in terms of hardness. The hardness unit is often expressed as "degree", 1 degree is equivalent to 10mg of CAO per liter of water, and the total hardness of drinking water is required to be less than 25 degrees.

2.Soft water Natural water with only a small amount of soluble calcium and magnesium salts, or hard water that has been softened. Natural soft water generally refers to river water, river water, and lake (freshwater lake) water.

Softened hard water refers to demineralized water obtained when the calcium and magnesium salt content is reduced to milligrams. Although boiling can turn temporarily hard water into soft water, it is extremely uneconomical to use this method in industry to treat large amounts of water. There are ways to soften water:

Lime - Soda method. First, the hardness of the water is determined, and then a certain amount of calcium hydroxide and sodium carbonate are added, and the calcium and magnesium ions in the hard water are precipitated and precipitated

ca(hco3)2＋ca(oh)22caco3↓＋2h2o

mg(hco3)2＋2ca(oh)2 mg(oh)2↓＋2caco3↓＋2h2o

CaSO4 Na2CO3CaCO3 Na2SO4 phosphate soft water method. For boiler water, sodium phosphite (Napo3) can be added as a water softener, which forms a complex with calcium and magnesium ions, and calcium and magnesium will not precipitate in the form of precipitation when the water is boiled, so that scale will not be formed. This method is not suitable for the softening of drinking water.

Ion exchange method. Although zeolite and ion exchanger are insoluble in water, the sodium ions and hydrogen ions in them can exchange with calcium and magnesium ions in hard water, so that calcium and magnesium ions are adsorbed by zeolite, artificial zeolite and ion exchangers and removed. Zeolite and ion exchangers that fail after long-term use can be reused by regeneration, so this method is both economical and advanced water softening method.

To put it simply, soft water is water with a small salt content such as calcium bicarbonate, calcium carbonate, and calcium hydroxide, and hard water is water with a relatively large content of these things. Mineral water groundwater is generally hard and hard, that is, hard water; Steamed water, pure water has a small hardness, even if it is soft water.

Hard water can be turned into soft water after ionic resin treatment, and soft water can be turned into hard water ......... by adding metal salt solutions or adding coral sand

It's not very prescriptive, but I think you should understand.

Categories: Lifestyle >> Lifestyle Encyclopedia.

Problem description: Thank you. Analysis:

Water is an important condition for human survival and an important part of the human body. Therefore, what kind of water you drink is crucial. Drinking water with excessive hardness can affect human health.

To understand this problem, we must first figure out what is the hardness of water. The hardness of water refers to the content of salts dissolved in water, that is, the amount of calcium salt and magnesium salt. The total amount of calcium and magnesium ions is equivalent to 10 milligrams of calcium chloride, which is called 1 "degree".

Usually according to the hardness, the water is divided into hard water and soft water: below 8 degrees is soft water, 8 16 degrees is medium water, above 16 degrees is hard water, and above 30 degrees is extremely hard water.

Hardness is further divided into temporary hardness and permanent hardness. Because the water contains calcium bicarbonate and magnesium bicarbonate and the hardness is formed, the hardness can be removed after boiling, and the hardness of the beam is called temporary hardness, also known as carbonate hardness; The hardness formed by the presence of salts such as calcium sulfate and magnesium sulfate in water cannot be removed after boiling, which is called permanent hardness. The above two types of hardness, temporary and permanent, are collectively called total hardness.

China's "Sanitary Standards for Domestic Water" stipulates that the total hardness of water shall not exceed 25 degrees. If the hardness is too large, it will have a certain impact on human health and daily life after drinking; If it is not for the occasional hard water drunk by people who regularly drink hard water, it will cause gastrointestinal disorders, which is the so-called "water and soil adaptation". If fish and vegetables are cooked in hard water, they will not be easy to cook, which will destroy the dust and reduce the nutritional value.

Brewing tea with hard water will change the color and aroma of the tea and reduce the pleasure of drinking. Making tofu with hard water will not only reduce the yield, but it will also affect the nutritional content of the tofu. The hardness of the water used to make wine should not exceed 4 degrees, otherwise the quality of the wine will be cloudy and the taste of the wine will be affected.

The hardness of water is calculated based on the amount of calcium and magnesium ions in the water, and the higher the content of these two ions, the harder the water will be. Hard water refers to water with a hardness of 16-30 degrees, such as spring water and deep well water flowing from the depths of the formation mostly belong to hard water, while soft water is water with a hardness of less than 8 degrees, such as rainwater, ponds, streams and other surface water belong to soft water. The current standard unit of hardness for water is mmol l (millimoles per liter).

The traditional units are mgn l (milligram equivalent per liter), German degree, American system (imperial system), etc., at present, the commonly used hardness units in China are mg l (milligrams per liter), mmol l (millimoles per liter), mgn l (milligram equivalent per liter), occasionally there are users who use German degrees, and the German degrees can be converted into the national standard value of millil l (millimoles per liter), if the American grain gallon (grains per gallon) is used, the unit needs to be converted many times. Water with more calcium and magnesium ions is called hard water, and water with less calcium and magnesium ions is called soft water. Hard water and soft water are just popular names, there is no standard amount of concept, in life, the industry generally the hardness of less than 3mmol l water is called softer water, 3-6 is called ordinary water, 6-8 is called harder water, more than 10 is called high hard water.

First of all, let's understand the relationship between calcium and magnesium ions and human health. Calcium and magnesium ions are essential nutrients for the human body every day, and if the water has a certain hardness, a certain amount of calcium and magnesium ions can be replenished by drinking water. People who have been taking soft water for a long time need to supplement it through other means.

In fact, it is not good for the hardness of water to be too high or too low, because the hardness of water is closely related to some diseases. The survey found that the incidence of cardiovascular disease was lower in areas with higher water hardness. The standard for drinking water in China is not to exceed 25 degrees, and the hardness of the most suitable drinking water is 8 18 degrees, which is mild or moderately hard water.

Soft and hard vs taste: The taste of water is also related to soft and hard, most mineral water has a high hardness, so it makes people feel refreshing and delicious, while soft water appears light and tasteless. However, when making tea with hard water and brewing coffee, the taste will be affected, so it is best to brew it with softer water when drinking tea, especially when drinking green tea.

Soft and hard vs body feeling: After taking a bath, it is hard water that feels smooth, and soft water that feels that it is not clean. 0

Hard water is water that contains more water-soluble calcium and magnesium compounds.

Soft water is water that contains fewer water-soluble calcium and magnesium compounds.

The way to distinguish between hard water and soft water is to add soap liquid to them and then stir them, the soft water with more soap bubbles and the hard water with less soap bubbles and disappear quickly.

The amount of 10 mg of calcium oxide or equivalent to 10 mg of calcium oxide per liter of water is called 1 degree. Hard water above 8 degrees Celsius and drinkable below 25 degrees Celsius.

Water that contains more calcium and magnesium plasma is hard water.

Drinking hard water for a long time is easy to get stone disease.

It refers to the water containing magnesium salt and the salt concentration is larger, and the hardness of the water is calculated as follows: the calcium ions and magnesium ions in the water are regarded as calcium ions, and their masses are converted into the mass of calcium oxide, and the ten milligrams of calcium oxide in one liter of water are called one degree, and so on.

According to this standard, hard water with a hardness of more than 8 degrees is called hard water, and more than 30 degrees is called the hardest water. The standard for tap water** is that the total hardness must not exceed 25 degrees. Water with high hardness is harmful to life and production.

Calcium and magnesium salts adhere to the boiler wall and form scale. Scale hinders heat transfer, resulting in a decrease in boiler thermal efficiency and accidents such as boiler damage.

The calcium and magnesium ions in the hard water interact with the soap to form a precipitate, which is the failure of the soap. Drinking water that is too hard can cause gastrointestinal upset.

Soft water is not harmful to the human body, and hard water is minerals that exceed the standard such as calcium, magnesium, iron, etc., which must be treated before they can be used.

pH 7 [neutral water]. pH value below 7 is acidic water [soft water] pH value greater than 7 is alkaline water [hard water].

If you don't see a lot of limescale, it's hard water, and it's soft water.

Modern scientific analysis believes that the water used to make tea is divided into soft water and hard water, the so-called soft water refers to the content of calcium ions and magnesium ions per liter of water is less than 10 milligrams, and the content of calcium ions and magnesium ions exceeds 10 milligrams that is hard water.

[Water hardness grade].

Soft water: 0-60ppm

Slightly hard water: 60-120ppm

Hard water: 120-180ppm

Very hard water: 181ppm or more.

Definition of hard water].

Hard water refers to water that has a lot of dissolved substances such as calcium bicarbonate and magnesium bicarbonate. Spring water, well water, etc., is often hard water.

The harm of hard water] hard water in addition to the harm to life (such as washing) and production (such as boilers), long-term drinking of water with high hardness also has an adverse impact on human health, in addition to many industrial sectors, such as textile, printing and dyeing, papermaking, chemical industry, etc., all require the use of soft water.

Hard water softening method].

1.Boiling is often used in daily life to reduce the hardness of water.

2.Distilled water is commonly used in laboratories to reduce the hardness of water3In industry, ion exchange method and agent softening method are commonly used to obtain soft water.

Common hard water] groundwater (such as well water, spring water), tap water [definition of soft water].

Soft water is water that does not contain calcium or magnesium compounds or contains less calcium or magnesium compounds than hard water.

Common soft water] distilled water, rain and snow water.

The difference between hard water and soft water].

Hard water is water that is dissolved with more calcium, magnesium substances; Soft water is water that has less or no calcium, magnesium or substances.

Hard water is formed due to rainwater dissolving into the compounds of calcium and magnesium contained in the stone:

caco3co2

h2o>ca2+

2hco3-

mgco3．

caco32co2

2h2o>ca2+

mg2++4

HCO3- In addition, hard water can be divided into temporary hard water and permanent hard water, and temporary hard water can become soft water after boiling:

2hco3-

co2+co32-h2o

co32-ca2+

caco3s)co32-

mg2+>mgco3

s) Calcium carbonate and magnesium carbonate are insoluble in water, and the tea scale in the teapot is also derived from this, so it is extremely difficult to clean.

The fresh water in Hong Kong is already soft, so we do not need to use ion exchangers.

ionexchangers)

To treat iron, calcium and magnesium in cleaning or heating water.

Hard water and scum (scum).

Students from Form 4 and above must think of scum when they see the word hard water, which is a new word that they learned in the lesson on detergent.

Are minerals in water really so useless?

In fact, they have a certain degree of influence on our physical health, according to an American medical journal.

journal

oftheamerican

medical

society)

It was reported before.

Dr. Henry.

drhenry

schroeder)

--- of the discovery

Areas with hard water** are better than none.

Mortality rates are low in areas with hard water**. In any case, we should not overdose so as not to repeat the previous consumption.

Excessive amounts of vitamins A and C.

Mineral water is a hard drink with a high mineral content.

More than five hundred parts per million), as the name suggests, is water from mineral springs.

-Rainwater flows into the stone layer, dissolves into various minerals, and then accumulates.

And carbonized mineral water are derived from natural, carbonate-containing stones such as limestone).

It dissolves in water and releases carbon dioxide gas.

During the production process, these gases are collected, and then the collected gases are added when the water is bottled to ensure that there is a certain air pressure in the bottle.

When making wine, the minerals contained in the water also affect the quality of the wine. Because hard water contains minerals to provide yeast nutrients, the quality of wine made from hard water will be better.