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Case-lesson "The formula of mud"
Case-lesson "The formula of mud"

Category: Science, nature and man

The level (grade): 8 +

Subject: Natural phenomena

Objective: Find out about the correlation between physical, chemical and biological characteristics of natural materials and applied aspects of their usage with the help of studying mud.

What information is waiting for me here?

  • What is mud in terms of chemistry? Why does soap wash it off?
  • Why do people, animals, and birds take mud baths?
  • Can mud be useful?
  • What fundamental and practical knowledge do I need?
  • What technology is not "afraid" of mud?
  • Can you go in for sports "in mud"?
6 scans of the subjects, phenomena and practices:

What is mud? This is a childish and naive question but it requires a full and profound answer. Mud is a mixed substance that has different physical and chemical properties.

Complex composition determines the "methods of dealing with it, and begets new questions. Why does soap wash it off? Can soap wash off all kinds of mud? Can mud be useful?


So what does mud consist of? Firstly, there are some inorganic components with particles of dust and soil, such as iron, potassium, magnesium, manganese, nitrogen, phosphorus, and others:


Secondly, there are also organic components. They depend on what we understand under the term "mud". If it is "natural" mud (in which some animal species like to bath), it is mainly the organic matter of plant residues. Plant residues are accumulated as the result of withering away of higher plants and their decomposition under conditions of excess moisture and lack of oxygen. Because of biochemical processes and vital functions of microorganisms, substances decompose to form volatile fatty acids, carbohydrates and amines.

If we are talking about dirty hands, their main organic component is fats. Moreover, if the organic matter contained in clays can be used as a detergent, fats of "dirty hands" are the main target for soap and shampoo. Scientists call the argillaceous part of mud a "clay core".

Therefore, mud is a colloidal solution that contains, in addition to water, such components as (on average, %):


Inorganic components of mud:


Organic components of mud:


Mud can be washed off with soap and water. We hear about it from the early childhood. So, how does soap "work", considering the chemical composition of mud?

The chemical formula of soap molecule is the following:


The action of soap is based on hydrophilicity. Hydrophilicity is the ability of a substance to interact with water at the molecular level (but hydrophobic substances, on the contrary, cannot interact with water). The COONa group provides the hydrophilicity of soap molecules. Owing) to this group, soap can be dissolved in water. And CH3—(CH2)n is a saturated hydrocarbon radical which is hydrophobic. The structure of this radical can contain up to 12 carbon atoms.

Soap as well as other detergents decreases the surface tension of water, improving the access of soap molecules to the surface that is being cleaned. During a washing process soap bubbles are formed.

Soap molecules are oriented in such way that hydrophilic groups COONa+ are directed to the polar water molecules, which are inside. They remain in water. Hydrophobic CH3—(CH2)n are directed upwards to the nonpolar mud particles. Mud contains fat. Fat is a compound of glycerol and those fatty acids. CH3—(CH2)n forms (with the particles of fat) suspension that can be easily removed with water.

The same scenario is suitable for all detergents based on surfactants.


What do you think is there any dependence between the amount of dirt and the intensity, required for sufficient hands washing?

At the heart of soap, “cleaning off dirt” process in terms of physics lies the phenomenon of surface tension. What is the surface tension?

The surface tension has a double physical essence – energy (thermodynamic) and power (mechanical).

The energetical thermodynamic definition is: the surface tension is the specific work that increases the surface when it is stretching under the condition of constant temperature.

The powerful (mechanical) definition is: the surface tension is the force that affects a unit of length of line that limits the surface of the liquid.


A drop of liquids on the surface of solids forms an angle to the surface. It is called the contact angle (angle of wetting). The size of the contact angle between liquids and solids depends on the interaction between substances on the contact surface. The less significant the interaction is, the greater the value of the contact angle is, as well:


After defining the contact angle, it is possible to find out about certain properties of the surface, such as surface energy. The wider the contact angle is, the harder it is to wet the surface, and the less foreign substances adhere to it. That is, to wash dirt away, you need to use substances that increase the contact angle and decrease wetting. Such substances are detergents, including soap.


It is usually said that mud is harmful; mud can cause many infectious diseases. Many infections are called "diseases of dirty hands".

Can mud be good for health?
It can, if we are talking about therapeutic mud.

The basis of the physiological effect of therapeutic mud is a complex effect on the body temperature, mechanical and chemical factors:


What types of mud are helpful”?


For example, the mud of Kuyalnik:

Therapeutic mud of Kuyalnik is a standard of physicochemical, biological and therapeutic properties of sulfide mud. Along with dissolved mineral salts, there are also organic substances and gases. Gases are formed by biological processes and by chemical reactions. This is hydrogen sulfide (odor of mud is conditioned by hydrogen sulphide primarily; it is an indicator of its therapeutic effectiveness), methane, carbon dioxide, hydrogen, etc.

If the gases content exceeds the solubility, they are allocated in a free state, forming so-called volatile complex. The volatile complex has the greatest ability to penetrate into human’s body through the intact skin.

Therefore, walking along the estuary Kuyalnik also gives a significant therapeutic effect.

Therapeutic mud of Kuyalnik contains up to 15 microelements —plumbum, iodine, copper, beryllium, molybdenum, zirconium, strontium, vanadium, manganese, titanium, nickel, cobalt, and others that participate actively in the regeneration of the body of human, who takes mud or salt baths.

The mud of the Dead Sea:

Over millions of years of existence of the Dead Sea a sedimentary layer in the form of slit of a thickness higher than 100 m was formed at its bottom. This layer is the world famous mud of the Dead Sea, which is so famous for miraculous healing properties, known from the depths of history. The ancient Romans and Jews used to build special hospitals on the shores of the Dead Sea.

The composition of the mud of the Dead Sea includes the following compounds: solid phase (calcite, aragonite, dolomite, mica, rock salt, kaolin (white clay), quartz, feldspar, sulfur iron, copper, and cobalt), liquid phase (magnesium, sodium, potassium, calcium, strontium, lithium, bromine, chlorides, sulphates, bicarbonates, iodine, manganese, gases (hydrogen sulfide, carbon dioxide, nitrogen, oxygen, and methane). In addition to that), Dead Sea mud contains hormone substances, compounds that resemble female and male sex hormones.

It is important to remember that mud is primarily a complex of substances of natural origin with very specific composition and side effects. Before applying them, you should consult a physician or cosmetologist.


What properties should mud have? What composition should it have in order to be therapeutic?
Why do some animals bath in mud? It does not happen because they are "sloppy". Moreover, it is not because they "have heard about the healing properties of mud". Here, for example, is a baby of rhinoceros taking a mud bath:

The most common explanation of this is in order to get rid of parasites. However, even this is not an exhaustive answer.

This «bathing» is required for thermoregulation. These animals have very little sweat glands, which would prevent overheating of the body due to the increasing intensity of evaporation, thereby cooling the entire body. Damp mud is a slow and at the same time efficient "refrigerator", which is more effective than just cold water in which these animals would immerse themselves. In addition, by bathing in mud, they can change their scent and disguise themselves from predators.

However, birds also like to “bath” in dust. Why do they do it?

In spring and summer, when birds sit in their nests, they often infested with small insect parasites. Birds begin to feel unpleasant itching, getting rid of which is possible only with special drugs або medicine or warm dust and sand. By lounging in sand birds clean their feathers and get rid of their intrusive “guests”. If birds do not do it in time, birds may lose feathers and attractiveness. Moreover, it is not a pleasant experience to live without some feathers in winter.
Some gamekeepers create real sand baths for animals.


Why do some children “come into” mud?

Is it possible to go in for sports in mud? Yes, mud may become an unusual playground. For example, off-road racing:

These races are not only an excellent sport activity but also an incentive for designers and engineers of SUVs and ATVs.
Another type of sport in mud is swamp soccer:


It is the variation або variety of football. It is held at the site with boggy soil. Esa Romppainen is considered the founder of the swamp soccer. The venue of the annual World Cup of swamp soccer is the Finnish village Hyrynsalmi. There is a marsh stadium "Vuorisuo" there. The rules are almost the same with the traditional football. However, there are few "amendments on mud": the game is played on a swamp, it is prohibited) to change boots during the match; the field size is 60х35 m; team includes five players and a goalkeeper; match consists of two halves of 13 minutes each, and penalties performed “by hands”.


Think about "your own" mud sport. What rules should be implemented? What are the benefits of this sport?

What technology can overcome mud? All-terrain vehicles, of course! However, which of them are the hardiest?
The most powerful all-terrain vehicle is Polaris RZR XP 1000 EPS. Its weight is 621 kg. It can be accelerated up to 80 km/h. in 5.5 seconds.

The largest (although not the most powerful one) all-terrain vehicle in the world is Heavy Mover. German company Paul Nutzfahrzeuge has created it. It is a truck for transporting heavy loads in off-road conditions. The car with a wheelbase 6x6 was released in 2012. It is designed for operating in areas where a very high permeability is demanded. It is able to operate even at -40°C:

The best amphibious all-terrain vehicle is the fantastic Scamander. The British has created it. Peter Wheeler has developed the car. It was his dream to create a modern amphibious all-terrain vehicle. He had been working for project two decades. Unfortunately, he had never seen the result. His wife and the company’s engineers have completed the work:

What all-terrain vehicle is the most suitable to carry cargo? Which of them are the most mud resistant considering their load capacity? It is the Mercedes Unimog. It is able to disperse high speed, to cope with any mud and to move with more than 7 tons of cargo:

Every time engineers meet new unusual tasks. Perhaps the next generations of brilliant engineers and inventors will have to overpass the mud of extraterrestrial colonies of mankind with all-terrain vehicles...

Lesson summary:


The contents


The results of the case-lesson can be complemented with findings of students



What three websites helped to find important information?






To help student and coach:






Where can you get information for the case?













Location of the lesson:

The case-lesson takes place in the classroom.

It is possible to hold the lesson at museum or library.



Teams of boys and girls.

The score was:....


1. Is it possible to combine the useful properties of mud and soap? How?

2. What all-terrain vehicle do you need to overcome volcanic mud?



Try to conduct a mini-study. You should use solid and liquid soap for some time (e.g. during a week). Write down which of them is better (washes away the dirt, foams better, and does not desiccate skin). Look at the packaging to determine what the soap consists of. Then try to explain its features in terms of its composition. Is there a connection between foam and cleanliness? Can you explain this in terms of physics? Prepare a report or presentation.



90 min (double lesson)      


The possibility to conduct the lesson with a student-understudy  

It is possible.


The acquired knowledge and developed competence:

• To expand and systematize some knowledge about natural materials and cleaning products.

• The ability to find necessary information quickly.

• To obtain comprehensive vision of the problem from the point of view of nature (biology, health) and technology.

• The ability of theoretical knowledge application and as well as practical skills in science.



Fatty acids, amines, fats, soap, clay skeleton, hydrophilicity, hydrophobicity, surface tension, wetting, contact angle, all-terrain vehicle, mud.



Hrabowska Larysa


Participated in the case upgrading:



The End

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