|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
ENTERTAINING EXPERIENCES AT HOME
Wash. Chemical experiments
Entertaining experiences at home / Chemistry experiments for children From dry cleaning it will be natural to move on to washing, which we will do. Washing is a physical and chemical process, its main actors are surfactants. The molecules of such substances consist of two parts - hydrophilic, that is, having an affinity for water, and hydrophobic, which does not interact with water, but willingly comes into contact with pollutants, for example, with difficult-to-wash fats and oils. These groups - hydrophilic and hydrophobic - are located at different ends of a long molecule. Such molecules attach their hydrophobic ends to the oily surface, while the hydrophilic ones stick out like needles on a hedgehog. Water wets these "needles" well, it surrounds such a "hedgehog", tears it off the surface and carries it away. This is how soap and laundry detergent work. And to quickly remove the dirt from the fabric or from our hands, we rub them with a sponge, a brush, against each other ... Since soap is the oldest surfactant, let's start with it. Dissolve a little soap in a small amount of water and add the phenolphthalein solution to the test tube. The color will turn crimson-red. This means the environment is alkaline. Indeed, ordinary soap is a sodium salt of fatty acids - oleic, stearic, for example, C17H35COONa (and liquid soap is a potassium salt of the same acids). When dissolved in water, such salts hydrolyze, decompose into an acid and an alkali. But fatty acids are weak, and alkalis in this case are strong, so the solution has an alkaline reaction. It used to be thought that soap washes and washes well because it forms alkali. It turned out that this was not the case at all. In contrast, an alkali (like washing soda) cleans because it combines with fats and forms soap-like surfactants in solution. By the way, soap is not that hard to get yourself. There are several ways; here is one of them. Prepare a hot concentrated solution of washing soda, pour it into a test tube and gradually, drop by drop, add vegetable oil until it no longer dissolves. Instead of oil, you can take beeswax. Pour a pinch of table salt into the resulting solution. So do soap factories - this process is called salting out. After adding salt, solid soap floats to the surface and is easily separated from the solution. Now soap for washing is used less and less, and washing powders are increasingly used. The composition of these powders includes surfactants obtained synthetically. That is why they are called synthetic detergents. Let's put this experience. Cut a piece of dirty cloth into three pieces and dip each piece into glasses. Pour just warmed water into the first glass, a soap solution into the second, and a solution of any washing powder that you can find at home into the third. Lightly rub the patches, rinse them in clean water, dry and carefully examine. That piece of cloth that had been in the water was not much cleaner. A piece of soapy solution brightened noticeably. But the cleanest will be the piece of fabric that you removed from the glass with a solution of washing powder. This means that synthetic detergents act more vigorously than ordinary soap. Many washing powders have another valuable property: they wash in any water - soft, hard, even sea water. What about soap? Take ordinary water and dissolve some calcium or magnesium salt in it. You can buy bitter salt at the pharmacy, you can take dry sea salt (it is also sold in pharmacies) or a solution of calcium chloride. Thus, you will make the water hard, because hard water differs from soft water in that it contains a lot of calcium and magnesium salts - the so-called hardness salts. Again, take a piece of dirty cloth and try washing it with soap in such hard water. Nothing will come of it - not even foam is formed. Hardness salts react with soap, calcium and magnesium soaps are formed, and they are insoluble in water. And our soap loses all its useful properties. But if you dissolve washing powder in hard water, for example, Lotus, it will wash dirt almost the same as before - hard water does not harm it. The surfactants that make up the powder do not interact with hardness salts, and therefore do not lose their properties. Solutions of washing powders, as well as solutions of laundry soap, can be alkaline; in this case, they recommend washing cotton and linen, but not wool or silk. However, there are also neutral agents, they are often produced not in the form of powders, but in the form of liquids; they are good for wool, silk and synthetic fabrics. If in doubt whether it is worth washing a wool sweater with one or another powder, then test with phenolphthalein. The solution turned red - it means that there is free alkali in it, and it is contraindicated for wool, because it can destroy the fibers. But if the solution remains colorless or stained quite a bit, feel free to immerse both woolen and silk items in it. In the old days, when soap was a luxury item, other, more affordable substances were often used for washing, which, although to a lesser extent, still washed off the dirt. Try and you, how these substances work. You can take mustard powder or a decoction of beans for the experiment, but even better - the roots of some plants, for example, primrose, crow's eye, cyclamen, cockle. These roots contain saponins - substances that have a washing effect (perhaps in old books you have come across such an expression - soap root). All these natural substances wash, of course, worse than soap, but you can easily make sure that they still wash. Let's finish the chapter on detergents with an experiment in which, by adding surfactants and thereby changing the surface tension of water, we will make an object move through the water. From a thin copper wire, make a flat spiral in several turns, lightly grease it with oil or petroleum jelly and lower it very carefully to the surface of the water. The surface tension of water prevents the spiral from sinking, and water does not wet it. Now, with a pipette, gently drop one drop of soapy water into the very middle of the spiral. The spiral will now begin to spin. Spreading over the surface, the soap solution reaches the end of the spiral, leaves it and develops a small jet thrust. When the spiral stops, drip the soap solution again - the rotation will resume. Such a spiral can serve as a device for determining the surface activity of various liquids. Replace the soap solution with another substance - the spiral will move at a different speed. If you drop a solution of table salt, then there will be no circular motion at all. And in a solution of washing powder, the spiral will quickly sink. It washes away the layer of oil that holds the wire in the water. Author: Olgin O.M.
▪ Experiences with stored energy
▪ Testing invert sugar by color reactions
Artificial leather for touch emulation
15.04.2024 Petgugu Global cat litter
15.04.2024 The attractiveness of caring men
14.04.2024
▪ Harsh winters coming due to global warming ▪ New isotope of fluorine obtained ▪ Roccat Torch studio grade USB microphone ▪ Neural noise helps you learn ▪ High-voltage intelligent power modules with increased current carrying capacity
▪ section of the site Protection of electrical equipment. Article selection ▪ article by Werther and Charlotte. Popular expression ▪ article What are the benefits of snow? Detailed answer ▪ article Translator. Job description ▪ article 1260 MHz Converter. Encyclopedia of radio electronics and electrical engineering ▪ VFO article with electronic tuning. Encyclopedia of radio electronics and electrical engineering
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
We recommend interesting experiments in physics:
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page