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Case-lesson “Soap – beauty and benefit”
Case-lesson “Soap – beauty and benefit”

Category: Practical skills

Level (grade): 5-9

Subject: personal care

Objective: Uncover the mystery of the ordinary soap; learn to use all its properties.

What information is waiting for me here?

  • How does soap work?
  • Is it possible to wash your hands in a wrong way?
  • How do people wash hands in space?
  • What fundamental and practical knowledge will I need?
  • Which soap is the best?
  • How do animals wash themselves?
8 scans of the subjects, phenomena and practices:

Soap is a “mysterious” beauty and benefit. And our case-lesson not only reveals the secrets of ordinary soap and helps gain important knowledge in the school subjects, but also provides an opportunity to acquire lots of necessary skills.

The cultivation of taste, positive thinking, teamwork, self-control, concern for quality, ingenuity and everyday skills – these are the competencies which can be learnt with the help of this case-lesson.

So tender and flavorful. It entices by notes of vanilla, the smell of berries and chocolate flavor. It can give good mood and gentle touch. Foam shines in the sun like a rainbow, glistens and allures to touch.


What are we talking about? About soap! One would like to call it “appetizing”, though despite the pleasurable, almost culinary smells, don’t try to taste it. It contains multiple chemicals, the portion of which is beneficial for your skin but not stomach.

So what mysteries are hidden in these flavored pieces, which are so easily transformed into jolly foam?


Everybody knows that it is vital to wash their hands with soap. But due to what properties does soap wash better than water alone? Is fact, soap is a big molecule, consisting of two particles: polar and nonpolar. Such substances are usually called surfactants because they are able to form pellicle on the surface of water – the active surface.

How does work? If we omit all the complicated terms, describing physical and chemical processes, we’ll get the following scheme of the procedure:


But how often can we use soap? Because there is a belief that over frequent usage of soap dries up the skin. Warning about the frequency of soap usage concerns antibacterial soap. After all, it contains a powerful active ingredient – triclosan – which kills harmful microorganisms. It's a good thing. However, in 10 days our skin grows accustomed to the fact that soap fights microbes for it, and its own mechanisms of skin protection are inhibited. The skin becomes vulnerable. Therefore it is important to have judicious approach to the application of these types of detergents.


Why does soap foam? panta-pani_com source explains this phenomena in the following way: A bubble is primarily air or any other gas enclosed into a thin membrane. If it is soap or washing powder foam, the shell of the bubble consists of molecules that, if you look at them under a microscope, are similar to pins with round heads and long edges.


The molecule’s “head” is made of hydrophilic material (which means the material that “loves” water; Greek “hydor” – water and “philia” – love). The long tail of the soap molecule is adopted from fat. Fats are “afraid” of water and don’t dissolve in it, that’s why they are called hydrophobic (Greek “phobos” – fear).

In the presence of water, these pin-molecules immerse their heads in water, and, clinging to each other, form a thin flexible film that can close itself and keep the air or other bodies. Soap is very rich in these pin-molecules – they are like little missiles, greedy for everything that is covered in fat.

When the piece of soap is being scrubbed by wet hands the emulsion between water, soap pin-molecules and particles of dirt is formed. For the pin-molecules this is a desirable prey. They attack these particles immediately and surround them, leaving only the heads in contact with water.

Thus, the bubbles of three types are formed: “pure” bubbles (containing only air), “less pure” (containing air and a small amount of dirt) and “dirty” (which contain a lot of dirt and very little air). “Less pure” bubbles are not as stable as the “pure” ones and don’t last long, while the “dirty” bubbles are very small in size and invisible. Hence, with the equal amount of soap clean water gives more stable and abundant foam than dirty water.

You can create big soap bubbles by yourselves:

Why does soap make your eyes sting? The substance that enables soap to foam is responsible for this effect as well! Chemists call it sodium lauryl sulfate. Soap is an alkaline substance, which is a strong irritant to the skin. And this alkali possesses the effect of “drying up” the skin.

But do you wash your hands properly? Yes, there are rules which should be followed in order to make your hands really clean and not just “covered in soap and water”.


Such “reminders” are frequently found in hospitals because clean hands are crucial for doctors.


Have you seen such “instructions” about the right approach to washing hands? Pay attention to the way you wash your hands. Is it correct?

Laundry soap is the soap that contains up to 72% of alkali. This is why laundry soap can be used in many various cases:

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How is soap manufactured? The process of manufacturing is basically boiling fats with alkalis. Fats are extracted from natural products of plant (cotton, palm or soybean oil) and animal (pig fat, beef or mutton fat, fish oil) origins.

It is possible to add various colorants, flavorings or any other beneficial attachments to soap.

Here is how the manufacturing process looks like:

Can you produce soap by yourself? Yes, you can; there are a lot of workshops on the topic. The simple way is to use a ready soap basis with attachments according to your wish and fantasy. The difficult one is to create the basis of fats, oils, alkalis and other ingredients. This variant requires experience, mastery and patience!


Make up “your own” soap: what color would it be and what shape? Perhaps, it would be multicolored? And what smell would it have? Draw it and write a short description next to your picture.


Is soap helpful? It’s hard to answer uniquely: soap is helpful to humans but it is harmful to the environment!

When we wash our hands soap, along with water, begins its “big journey”:


This is why it is vital to remember that soap shouldn’t be used beyond the required for washing amount!


Create an ecological sign that would remind people about the ecological danger which the ordinary soap possesses.

And what kind of soap do astronauts use? There is no running water at the space station, so it is impossible to take a shower or bath in the familiar to us form. Space ship’s bathroom is called “the hygiene corner”. Here is a cosmetic bag Comfort 1M where soap, deodorant, shampoo and toothpaste can be found.

There are no washing machines as well so you won’t have the possibility to launder a towel. That’s why towels are delivered at the station as needed and as it is possible to actually deliver them into space.

Soap is contained in special packages. Astronauts pour water in them to dilute it.

Such soap doesn’t require washing off because it doesn’t foam.

Water is not running but hangs in the air in big drops, which can be caught with a towel and used for washing. Water isn’t evaporated – it stays on the towel; this is why later it can be regenerated and return to the station’s water cycle.

For how long have humans been using soap? Scientists believe that people have been using soap for almost 6 000 years! People in ancient Egypt had already started boiling soap. The proofs are these old pictures:


The ancient Sumerians (2 500 years ago) also produced and used soap. They were using special clay tablets for writing. On one of such tablets, preserved to this day, the recipe of Sumerian soap was found.


Ancient Greeks and Romans had also used soap. Soap making became a separate craft, there were whole workshops. Soap had been called “sapo”, and soap-boilers – “saponariusi”. Even in Pompeii, the city, destroyed by the eruption of Vesuvius, the remains of soap have been found.

The times have been changing, and soap making, as a craft, has remained in the east for some time. To Europe soap had been brought by knights, who had been bringing soap balls when returning from crusades.

The European soap making craft originates from the XII century. Fashion for soap and cleanliness occurred in XVII century. After the opening of an industrial production of soda by chemist Nicolas Leblanc soap became more accessible. As far as soda was required for making soap, the more cheap soda existed, the more affordable soap could be produced.

In the modern world soap has become the basis of large productions, provided the impetus for the development of brands, become a branch of the exquisite art and a simple hobby.


And what the soap of the future will look like? Most likely it will be hard to recognize the familiar pieces of fragrant soap.

Scientists from the University of Southampton have found a way of cleaning without the use of chemicals. They have turned to… bubbles.

The technology has been called Starstream. With the help of ultrasound air bubbles move in such way so they clean the surface to which they are applied. Moreover, according to the scientists, they also disinfect it.


What soap would you like to use: the modern or the future one?


Soap can be a foundation of art or even a folk craft – art, traditional in a particular country, culture or location.

In Taiwan soap carving is traditional art, preserved in many villages. It is believed that every artist has their own technique of carving, their own secret tricks so their products become real masterpieces.


Both men and women can become artists. Even teenagers can master the soap carving technique. This branch of art is called “carving”.

Here’s how the “soap miracles” are created:


What soap figure would you like to make?

Natural science
Do animals wash themselves? Not all animals bath in water. Some of them use dust or mud for cleaning as a substitute for soap.

Cleaning the integuments is very important for all animals, so many of them have special habits and different methods of mutual help when it comes to cleaning their fur or feathers. Herons and bitterns have fuzz – so called “powderette” – on their chests and abdomens, which is constantly growing.


Dying tips of this fuzz form the fine “powder”. Birds use it as talc, through which they get rid of the excessive amounts of fat, various contaminants. They distribute this “powder” throughout the plumage with their beaks. For better penetration of the “powder” birds bristle their feathers.

Slow loris has long thick claws adapted for combing fur.


These claws are placed on the second fingers of the hind limbs, they replace the ordinary nails. With special claws animals comb their fur out like with a comb.

Aye-aye, also known as Daubentonia madagascariensis, is a rare animal. It uses an extremely long and thin middle finger on the front paw for the same purpose. With its help it gets parasites out of its fur.


Anteaters also have a long finger armed with a large claw on their hind limbs, with the help of which they get rid of parasites that get entangled into their tough fur.

Even bats lick the flying membrane, thus treating the wounds from parasites’ bites.


What other animals’ hygiene habits, which help them replace soap, do you know?


Where does the price of soap come from? Why does one kind cost 25 UAH and another – 250 UAH? Is this because one type of soap is prettier or more fragrant than another? So what does affect the price of soap?

First of all, the main factor is the materials from which soap is made – soap basis. If it is an industrial production, we should consider the production costs – electricity, water and so on. Raw materials are brought, ready soap is transported, so there are also transportation costs. All of these details are handled by people – employees of the company. Salaries are also taken into account when the cost of soap is calculated. The result is the selling price – the price which is issued by the soap’s manufacturer.

A buyer – a large wholesale company – buys soap and sells it to smaller companies (called retail companies). Each of them add margin to the price because they literally earn money through this.

There are also taxes. Those are the funds that the company pays the state. Beyond taxation there are also duties (for example, in the case if the raw materials have come from abroad) and other expenses. They are also reflected on the labels that you see at stores. When you go to a store the next time, pay attention to labels: there are usually two prices written there – the price for the product and the price with VAT (taxation for the added cost). This is one type of taxes.



When you go to a store the next time, pay attention to the prices of soap. Does VAT noted on the labels? What do you think, why the prices for soap differ? Do they depend on the size of the packaging?

Lesson’s summary:

The End

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