Salads 

Can salt dissolve in water? How to make a saline solution? Mixture separation methods

Education Department of the Administration of the Ardatovsky Municipal District of the Nizhny Novgorod Region

Municipal educational institution

"Ardatovskaya secondary school No. 1"

Competition of research works and projects for children of preschool and primary school age "I am a researcher"

Nomination: Ecological and biological activity

"Where does the salt go?

if dissolved

her in the water?"

I've done the work:

Plotov Gleb Yurievich - 8 years old,

2nd grade student

Supervisor:

Makurina Marina Nikolaevna,

primary school teacher

p.g.t. Ardatov

2008

Explanatory note of the head.

I have been a primary school teacher for over 20 years. And children of elementary grades are very inquisitive, they are interested in knowing everything. Why is the earth round? Where do rivers flow? Why is it snowing? Where does sugar go when it is thrown into a cup of hot tea? Why is lemon sour and banana sweet? All these and other similar questions need to be answered. But what if the children themselves find the answers to their questions? I decided on a small experiment - I invited the most inquisitive student to conduct a study on the question "Where does the salt go if you dissolve it in water?" And so, forward, in search of salt!

    Introduction……………………………………………………………….4 p.

    Research methodology and technique…………………………………..6 p.

    The results of the study and their discussion…………………………7 p.

    Conclusions………………………………………………………………...8 p.

    List of used literature………………………………...9 p.

    Application………………………………………………………… 10 pages

1. Introduction.

I am in the second grade, I learned a lot of necessary and interesting things, but how much more I want to know! I like to read educational books and learn a lot of interesting things from them. And once my mother asked me to salt the water for pasta. I dropped a small spoonful of salt into the bowl, then stirred and saw that the salt was gone. Where did she go? It became interesting to me. The next day, I asked my teacher about it, and she advised me to do the research myself, of course, with her help. But first I decided to find out everything about salt, what it is, where it comes from.

Purpose of my research

– find out where the salt goes when you dissolve it in water.

Tasks:

- learn about what salt is, where it is mined

- to conduct experiments on the dissolution of salt in water and the evaporation of salt from a saline solution.

- draw conclusions from the results of my research

“Salt is a crystalline substance that dissolves well in water. There is a lot of it in the seas, where it enters from tributaries. In turn, river water absorbs it from the soil through which it flows.

Salt, or sodium chloride. - a substance extremely important for life. The human body also contains quite a lot of salt. It is also found in natural foods. But we love it so much that we always add it to our food. The salt we eat is mostly extracted from sea water. One liter of it contains 30-40 grams of salt.” . (“Everything about everything” Popular encyclopedia for children. Volume 8. / G. Shalaeva 1994, pp. 280-281.)

“Salt is extracted from salt mines, springs, salt lakes and from the sea.

In the salt mines, the tunnels and corridors sparkle as if they were made of ice. The miners cut blocks, which are then broken into pieces, loaded into trolleys and transported upstairs on special trains. In some places, salt is mined through special salt wells. Wells are usually drilled to extract water. In salt wells, on the contrary, hot water is poured. The water spreads underground and dissolves the salt. Brine is formed underground. Then the brine is pumped out and heated in huge tanks. There the water evaporates and the salt settles to the bottom.

Sometimes the underground river of rock salt deposits is crossed by underground rivers. Then the water dissolves the salt, and salt caves form underground.

The largest salt caves are located in the Czech Republic, near the village of Velichka.

Salt is mined in another way. On the seashore, special shallow pools are built - salt presses. Sea water is let into them through a special channel.

The hot sun heats the water, and it quickly evaporates, and the salt brought by it remains in the pool.

In ancient times, salt was brought to Europe from afar. It was mined mainly in coastal areas and on some salt lakes.

That is why salt was highly valued, along with precious metals. In some places, salt was even used as a substitute for money.

There are two such lakes in Russia - Elton and Baskunchak. Salt was mined on their shores in ancient times.

Salt plays a huge role in human life, it is not only eaten. Previously, it was the main substance for preserving food from spoilage. (“Everything about everything” Popular encyclopedia for children. Volume 11. / G. Shalaeva 1999, pp. 277-278)

2. Methodology and technique of research.

Experiment No. 1 Dissolution of salt in water.

    Tap water is taken and tasted. (photo 1)

    Then the salt tastes the same. (photo 2)

    Then the water is tested, with salt mixed in it. (photo 5)

    Salt solution is poured into an aluminum pan and put on fire. (photo 6)

    Monitoring the state of the solution. (photo 7)

    Determine the taste of the formed white plaque - “flies”. (photo 8,9)

    Examine salt under a magnifying glass. (photo10)

    Examine under a magnifying glass a white coating formed in the pan after the water has evaporated. (photo 11)

3. Results of the study and their discussion.

Experience number 1. Dissolution of salt in water.

    Water has no taste.

    Salt has a salty taste.

    After stirring the salt in the water is not visible.

    The water has become salty.

Experience number 2. Evaporation of salt from brine.

    After boiling, the water gradually begins to evaporate, and then completely disappeared.

    White "flies" appeared on the walls and at the bottom of the pan.

    The taste of "flies" is salty.

Experience number 3. Comparison of food salt and "flies"

    Salt is soda transparent pebbles - crystals of various shapes and volumes.

    "Flies" - white and much smaller than salt crystals, look like powder.

4. Conclusions.

Conclusion 1. If you mix salt in water, the water becomes salty. But the salt itself is not visible in the water. From all this it follows that the salt was dissolved in water.

Conclusion 2 - When moisture is evaporated from the brine, the salt remains on the walls and at the bottom of the pan, turning into a white powder - “flies”.

Conclusion 3 Salt dissolves in water and breaks into small particles.

General conclusion So, the salt from the water does not go anywhere. Just salt crystals, falling into the water, break up into such small particles that they are not visible. But at the same time, they exist, because after the evaporation of water, a white coating remains, formed from these invisible particles, which has a salty taste. And we can say that particles of salt and particles of water are friends. They stretch out their hands to each other, joining in a strong handshake - a saline solution.

    List of used literature.

    Everything about everything. Popular encyclopedia for children. Volume 8. Compiled by: G. Shalaeva. Philological Society "Slovo" AST. Center for the Humanities at the Faculty of Journalism of Moscow State University. M.V. Lomonosov., M., 1994

    Everything about everything. Popular encyclopedia for children. Volume 11. Compiled by: G. Shalaeva. Philological Society "Slovo" AST. Center for the Humanities at the Faculty of Journalism of Moscow State University. M.V. Lomonosov., M., 19 99

6. Application.

Photo 1.Plain tap water is taken and tasted



Photo 2. Then the salt tastes the same.


Photo 5. Then the water is tested, with salt mixed in it.

Photo 6. Salt solution is poured into an aluminum pan and put on fire.

Photo 7. Monitoring the state of the solution.


Photos 8 and 9. Determine the taste of the formed white plaque - “flies”.

Photo 10. Examine salt under a magnifying glass.

Photo 11. Examine under a magnifying glass a white coating formed in the pan after the water has evaporated.

Salt solution is a very effective antiseptic and is therefore widely used as a first aid and home therapeutic treatment for various infections.

Saline preparation

This is a very simple process, since the salt is very soluble in water. It should be taken into account that for medicinal purposes saline solutions can only be prepared from pure sea or table salt.

  1. To prepare the solution, you need to take a container with the right amount of water.
  2. Add salt in the given proportions.
  3. After that, mix the solution thoroughly until the salt is completely dissolved. Salt dissolves much faster in hot water.

Salt rinse

For inflammation of the upper respiratory tract, a saline solution is used to wash the nasopharynx and gargle in proportions of 1/2 teaspoon of salt per glass of water. In the treatment of angina, for greater effectiveness, you can add 1/2 teaspoon of soda to the solution. This solution is used for rinsing the mouth with gum disease or other inflammatory processes in the oral cavity.

Salt solution for lotions and compresses

For external treatment, saline compresses are sometimes used or lotions are made to promote the healing of small wounds and the resorption of hematomas. To do this, use a solution with a concentration of 3-5 tablespoons of salt per glass of water.

For serious bruises, you can make warm compresses with a solution of salt in water in a proportion of 100 grams per 1/2 liter.

Saturated salt solution

To prepare a saturated solution, salt is gradually added to water and stirred until completely dissolved.

This continues until the dissolution of the salt ceases. If salt does not dissolve in water during prolonged stirring, but settles at the bottom of the glass, then its content in water has reached the maximum possible under normal conditions. Such a solution is called saturated. It can be used, for example, to grow salt crystals.

A salt can be defined as a compound that is formed by the reaction between an acid and a base, but is not water. In this section, those properties of salts that are associated with ionic equilibria will be considered.

salt reactions in water

Somewhat later it will be shown that solubility is a relative concept. However, for the purposes of the following discussion, we can roughly classify all salts into water-soluble and water-insoluble salts.

Some salts, when dissolved in water, form neutral solutions. Other salts form acidic or alkaline solutions. This is due to the occurrence of a reversible reaction between salt ions and water, as a result of which conjugate acids or bases are formed. Whether a salt solution is neutral, acidic, or alkaline depends on the type of salt. In this sense, there are four types of salts.

Salts formed by strong acids and weak bases. Salts of this type, when dissolved in water, form an acidic solution. Let's take ammonium chloride NH4Cl as an example. When this salt is dissolved in water, the ammonium ion acts as

The excess amount of H3O+ ions formed in this process determines the acidic properties of the solution.

Salts formed by a weak acid and a strong base. Salts of this type, when dissolved in water, form an alkaline solution. As an example, let's take sodium acetate CH3COONa1 The acetate ion acts as a base, accepting a proton from water, which in this case acts as an acid:

An excess of OH- ions formed in this process determines the alkaline properties of the solution.

Salts formed by strong acids and strong bases. When salts of this type are dissolved in water, a neutral solution is formed. Let's take sodium chloride NaCl as an example. When dissolved in water, this salt is completely ionized, and, therefore, the concentration of Na+ ions is equal to the concentration of Cl- ions. Since neither ion enters into acid-base reactions with water, there is no formation of an excess amount of H3O + or OH ions in the solution. Therefore, the solution is neutral.

Salts formed by weak acids and weak bases. An example of salts of this type is ammonium acetate. When dissolved in water, the ammonium ion reacts with water as an acid, and the acetate ion reacts with water as a base. Both of these reactions are described above. An aqueous solution of a salt formed by a weak acid and a weak base can be weakly acidic, slightly alkaline, or neutral, depending on the relative concentrations of H3O+ and OH- ions formed as a result of the reactions of cations and anions of the salt with water. It depends on the ratio between the values ​​of the dissociation constants of the cation and anion.





































Back forward

Attention! The slide preview is for informational purposes only and may not represent the full extent of the presentation. If you are interested in this work, please download the full version.

The purpose of the lesson: study of the properties of water.

Lesson objectives: to give an idea of ​​water as a solvent, of soluble and insoluble substances; introduce the concept of "filter", with the simplest ways to determine soluble and insoluble substances; prepare a report on the topic “Water is a solvent”.

Equipment and visual aids: textbooks, anthologies, notebooks for independent work; sets: glasses empty and with boiled water; boxes with table salt, sugar, river sand, clay; teaspoons, funnels, paper napkin filters; gouache (watercolors), brushes and sheets for reflection; presentation made in Power Point, multimedia projector, screen.

DURING THE CLASSES

I. Organizational moment

U. Good morning everyone! (Slide 1)
I invite you to the third meeting of the school science club "We and the world around us."

II. Message about the topic and purpose of the lesson

Teacher. Today we have guests, teachers from other schools who came to the meeting of the club. I propose to the chairman of the club, Poroshina Anastasia, to open the meeting.

Chairman. Today we have gathered for a club meeting on the topic “Water is a solvent”. The task for all those present is to prepare a report on the topic “Water is a solvent”. In this lesson, you will again become researchers of the properties of water. You will study these properties in your laboratories, with the help of "consultants" - Mikhail Makarenkov, Olesya Starkova and Yulia Stenina. Each laboratory will have to perform the following task: to conduct experiments and observations, and at the end of the meeting, discuss the plan for the message "Water - solvent".

III. Learning new material

U. With the chairman's permission, I would like to make the first announcement. (Slide 2) The same session on the topic “Water is a solvent” was recently held by students from the village of Mirny. The meeting was opened by Kostya Pogodin, who reminded everyone present of another amazing property of water: many substances in water can break down into invisible tiny particles, that is, dissolve. Therefore, water is a good solvent for many substances. After that, Masha proposed to conduct experiments and identify ways by which it would be possible to get an answer to the question of whether a substance dissolves in water or not.
U. I suggest that you at a club meeting determine the solubility in water of substances such as table salt, sugar, river sand and clay.
Let's assume which substance, in your opinion, will dissolve in water, and which will not. Express your assumptions, guesses and continue the statement: (Slide 3)

U. Let's think together what hypotheses we will confirm. (Slide 3)
Suppose ... (salt will dissolve in water)
Let's say ... (sugar will dissolve in water)
Perhaps ... (sand will not dissolve in water)
What if... (clay won't dissolve in water)
U. Come on, and we will conduct experiments that will help us figure it out. Before work, the chairman will remind you of the rules for conducting experiments and distribute cards on which these rules are printed. (Slide 4)
P. Look at the screen where the rules are written.

"Rules for conducting experiments"

  1. All equipment must be handled with care. They can not only be broken, they can also get hurt.
  2. During work, you can not only sit, but also stand.
  3. The experiment is conducted by one of the students (the speaker), the rest silently observe or, at the request of the speaker, help him.
  4. The exchange of opinions on the results of the experiment begins only after the speaker allows it to begin.
  5. You need to talk to each other quietly, without disturbing the others.
  6. Approaching the table and changing laboratory equipment is possible only with the permission of the chairman.

IV. Practical work

U. I suggest that the chairman choose a "consultant" who will read aloud from the textbook (p. 85) the procedure for conducting the first experiment. (Slide 5)

1) P. Spend experience with salt. Check if table salt dissolves in water.
A "consultant" from each laboratory takes one of the prepared sets and conducts an experiment with table salt. Boiled water is poured into a transparent glass. Pour a small amount of table salt into the water. The group observes what happens to the salt crystals and tastes the water.
The chairman (as in the KVN game) reads the same question to each group, and representatives from the laboratories answer them.
P.(Slide 6) Has the transparency of the water changed? (Transparency has not changed)
Has the color of the water changed? (Color has not changed)
Has the taste of water changed? (Water turned salty)
Can we say that the salt has disappeared? (Yes, she disappeared, disappeared, she is not visible)
U. Make a conclusion. (Salt dissolved)(Slide 6)

P. I ask everyone to proceed with the second experiment, for which it is necessary to use filters.
U. What is a filter? (A device, device or structure for purifying liquids, gases from solid particles, impurities.)(Slide 7)
U. Read aloud the procedure for performing the filter experiment. (Slide 8)
Students pass water with salt through a filter, observe and examine the taste of water.
P.(Slide 9) Is there any salt left on the filter? (There is no edible salt left on the filter)
Has the taste of water changed? (The taste of the water has not changed)
Have you been able to remove the salt from the water? (Table salt passed through the filter with water)
U. Make a conclusion from your observations. (Salt dissolved in water)(Slide 9)
U. Has your hypothesis been confirmed?
U. Everything is correct! Well done!
U. Write the results of the experiment in writing in the Notebook for independent work (p. 30). (Slide 10)

2) P.(Slide 11) Let's do the same an experience again, but instead of salt, put a teaspoon granulated sugar.
A "consultant" from each laboratory takes a second set and runs an experiment with sugar. Boiled water is poured into a transparent glass. Pour a small amount of sugar into the water. The group observes what is happening and examines the taste of the water.
P.(Slide 12) Has the transparency of the water changed? (The transparency of the water has not changed)
Has the color of the water changed? (The color of the water has not changed)
Has the taste of water changed? (Water turned sweet)
Can we say that sugar is gone? (Sugar became invisible in water, water dissolved it)
U. Make a conclusion. (Sugar dissolved)(Slide 12)

U. Pass water with sugar through a paper filter. (Slide 13)
Students pass water with sugar through a filter, observe and examine the taste of water.
P.(Slide 14) Is there any sugar left on the filter? (Sugar is not visible on the filter)
Has the taste of water changed? (The taste of the water has not changed)
Have you managed to clear the water of sugar? (Water could not be purified from sugar, along with water it passed through the filter)
U. Make a conclusion. (Sugar dissolved in water)(Slide 14)
U. Has the hypothesis been confirmed?
U. Right. Well done!
U. Write the results of the experiment in writing in a notebook for independent work. (Slide 15)

3) P.(Slide 16) Let's check the statements and conduct river sand experience.
U. Read the procedure for conducting the experiment in the textbook.
Experiment with river sand. Stir a teaspoon of river sand in a glass of water. Let the mixture stand. Observe what happens to the grains of sand and water.
P.(Slide 17) Has the transparency of the water changed? (Water became cloudy, dirty)
Has the color of the water changed? (The color of the water has changed)
Are the grains gone? (Heavier grains of sand sink to the bottom, while smaller ones float in the water, making it cloudy)
U. Make a conclusion. (Sand didn't dissolve)(Slide 17)

U.(Slide 18) Pass the contents of the glass through a paper filter.
Students pass water with sugar through a filter, observe.
P.(Slide 19) What passes through the filter and what remains on it? (Water passes through the filter, but the river sand remains on the filter and the grains of sand are clearly visible)
Was the water cleared of sand? (The filter helps to clean the water of particles that do not dissolve in it)
U. Make a conclusion. (River sand did not dissolve in water)(Slide 19)
U. Was your assumption about the solubility of sand in water correct?
U. Excellent! Well done!
U. Write the results of the experiment in writing in a notebook for independent work. (Slide 20)

4) P.(Slide 21) Do the same experiment with a piece of clay.
Experiment with clay. Stir a piece of clay in a glass of water. Let the mixture stand. Observe what happens to clay and water.
P.(Slide 22) Has the transparency of the water changed? (Water turned cloudy)
Has the color of the water changed? (Yes)
Did the clay particles disappear? (Heavier particles sink to the bottom, while smaller ones float in the water, making it cloudy)
U. Make a conclusion. (Clay did not dissolve in water)(Slide 22)

U.(Slide 23) Pass the contents of the glass through a paper filter.
P.(Slide 24) What passes through the filter and what remains on it? (Water passes through the filter, and undissolved particles remain on the filter.)
Has the water been cleared of clay? (The filter helped clear the water of particles that didn't dissolve in the water)
U. Make a conclusion. (Clay does not dissolve in water)(Slide 24)
U. Has the hypothesis been confirmed?
U. Well done! Everything is correct!

U. I ask one of the group members to read the conclusions written in the notebook to all those present.
U. Does anyone have any additions or clarifications?
U. Let's draw conclusions from the experiments. (Slide 25)
Are all substances soluble in water? (Salt, granulated sugar dissolved in water, but sand and clay did not dissolve.)
Is it always possible to use a filter to determine whether a substance is soluble in water or not? (Substances dissolved in water pass through the filter along with water, while particles that do not dissolve remain on the filter)

U. Read about the solubility of substances in water in the textbook (p. 87).

U. Describe the property of water as a solvent. (Water is a solvent, but not all substances dissolve in it)(Slide 25)

U. I advise club members to read the story in the anthology "Water is a solvent" (p. 46). (Slide 26)
Why have scientists not yet been able to obtain absolutely pure water? (Because hundreds, maybe thousands of different substances are dissolved in water)

U. How do people use the property of water to dissolve certain substances?
(Slide 27) Tasteless water becomes sweet or salty due to sugar or salt, as water dissolves and acquires their taste. A person uses this property when preparing food: brews tea, cooks compote, soups, salts and preserves vegetables, prepares jam.
(Slide 28) When we wash our hands, wash or bathe, when we wash clothes, we use liquid water and its solvent property.
(Slide 29) Gases, in particular oxygen, also dissolve in water. Thanks to this, fish and others live in rivers, lakes, seas. In contact with air, water dissolves oxygen, carbon dioxide and other gases that are in it. For living organisms that live in water, such as fish, oxygen dissolved in water is very important. They need it to breathe. If oxygen did not dissolve in water, then water bodies would be lifeless. Knowing this, people do not forget to oxygenate the water in the aquarium where the fish live, or cut holes in the ponds in winter to improve life under the ice.
(Slide 30) When we paint with watercolors or gouache.

U. Pay attention to the task written on the board. (Slide 31) I propose to draw up a collective speech plan on the topic “Water is a solvent”. Discuss it in your laboratories.
Listening to plans on the topic “Water is a solvent” compiled by students.
U. Let's all come up with a plan together. (Slide 31)

Approximate speech plan on the topic “Water is a solvent”

  1. Introduction.
  2. Dissolution of substances in water.
  3. Conclusions.
  4. People use the property of water to dissolve certain substances.

Excursion to the "Exhibition Hall".(Slide 32)

U. When preparing a report, you can use additional literature selected by the guys, assistant speakers on the topic of our meeting. (Draw students' attention to the exhibition of books, Internet pages)

V. Summary of the lesson

What property of water was investigated at a club meeting? (Property of water as a solvent)
What conclusion did we come to by examining this property of water? (Water is a good solvent for some substances.)
Do you think it's hard to be explorers?
What seemed the most difficult, interesting?
Will the knowledge acquired during the study of this property of water be useful to you in later life? (Slide 33) (It is very important to remember that water is a solvent. Water dissolves salts, among which there are both beneficial and harmful to humans. Therefore, you cannot drink water from a source if you do not know whether it is pure. It is not in vain that people have Proverb: Not all water is good for drinking.

VI. Reflection

How do we use the property of water to dissolve certain substances in art classes? (When we paint with watercolors or gouache)
I suggest you, using this property of water, paint the water in a glass in a color that best suits your mood. (Slide 34)
"Yellow color" - joyful, bright, good mood.
"Green color" - calm, balanced.
"Blue color" - a sad, sad, dreary mood.
Show your sheets of colored water in a glass.

VII. Evaluation

I would like to thank the chairman, the "consultants" and all participants of the meeting for their active work.

VIII. Homework

Water is one of the main chemical compounds on our planet. One of its most interesting properties is the ability to form aqueous solutions. And in many areas of science and technology, the solubility of salt in water plays an important role.

Solubility is understood as the ability of various substances to form homogeneous (homogeneous) mixtures with liquids - solvents. It is the volume of the material that is used to dissolve and form a saturated solution that determines its solubility, comparable to the mass fraction of this substance or its amount in a concentrated solution.

According to their ability to dissolve, salts are classified as follows:

  • soluble substances include substances that can be dissolved in 100 g of water more than 10 g;
  • sparingly soluble are those whose amount in the solvent does not exceed 1 g;
  • the concentration of insoluble in 100 g of water is less than 0.01.

In the case when the polarity of the substance used for dissolution is similar to the polarity of the solvent, it is soluble. At different polarities, most likely, it is not possible to dilute the substance.

How dissolution occurs

If we talk about whether salt dissolves in water, then for most salts this is a fair statement. There is a special table according to which you can accurately determine the amount of solubility. Since water is a universal solvent, it mixes well with other liquids, gases, acids and salts.

One of the clearest examples of the dissolution of a solid in water can be observed almost every day in the kitchen, while preparing dishes using table salt. So why does salt dissolve in water?

From the school chemistry course, many remember that the molecules of water and salt are polar. This means that their electrical poles are opposite, which results in a high dielectric constant. Water molecules surround ions of another substance, for example, as in our case, NaCl. In this case, a liquid is formed, which is homogeneous in its consistency.

Temperature effect

There are several factors that affect the solubility of salts. First of all, this is the temperature of the solvent. The higher it is, the greater is the value of the diffusion coefficient of particles in the liquid, and the mass transfer occurs faster.

Although, for example, the solubility of common salt (NaCl) in water practically does not depend on temperature, since its solubility coefficient is 35.8 at t 20 ° C and 38.0 at 78 ° C. But copper sulfate (CaSO4) with increasing temperature water dissolves worse.

Other factors that affect solubility include:

  1. The size of the dissolved particles - with a larger area of ​​phase separation, the dissolution occurs faster.
  2. A mixing process that, when performed intensively, contributes to a more efficient mass transfer.
  3. The presence of impurities: some accelerate the dissolution process, while others, hindering diffusion, reduce the rate of the process.