My Science School

               Ice columns appear in many caves or caverns. They are called stalactites and stalagmites. Stalactites are the stony deposits hanging like icicles from roofs of the caves. Stalagmites are similar deposits rising in columns and cones from floors of the caves. Do you know how are they formed?

               Most of the caves occur chiefly in lime stone and chalk formations. Limestone is a fairly soft rock mainly made of calcium carbonate that can be dissolved by a weak acid. The acid that dissolves limestone comes from rain water. Falling drops of rain pick up carbon-dioxide from the air. This carbon dioxide changes the rain water into carbonic acid that dissolves the limestone. The seepage of water down the cave walls and through the roof produces constant dripping and evaporation. Stone icicles formed on the cave roof, slowly grow with the addition of successive layers of calcium carbonate. The word ‘stalactite’ has Greek origin and means ‘drop by drop’. This is why these stone icicles are also known as “dripstone”.

               At the initial stage, the stalactite remains hollow due to faster, carbonate deposit at the outer ring of the water drops. However it slowly turns to solid when the cavity fills up in the process of evaporating the water particles from the mineral substances.

               If the seepage of water is quick the drop might fall on the cave’s floor. It deposits its calcium carbonate there and cones and domes of stone are formed. These are called as stalagmites. They may grow up to join the stalactites above and form single columns. They may even grow as high as to block the entrance of the cave. Each stalactite or stalagmite grows at a different rate, depending on the wetness of the cave, the inside temperature of the cave and the thickness of the limestone bed above it. Some stalactite might grow an inch a year while others would take one hundred years or so to grow that much. When water stops reaching the underground caves, the stalactites stop growing and the cave is considered “dead”. 

               It has been estimated through scientific analysis that the water of the seas contains about four and a half million solid cubic miles of salt. All these salts have reached into the seas from the earth. The rain water and melted snow water dissolve minerals from rocks and flow down through the rivers into the oceans and seas. These are main sources of salt deposits in ocean and sea water. It has been found that on the whole sea water contains about three to three-and-half percent of common salt. But millions of years ago evaporation took place from the water of bays, which were cut off from the sea and became salt lakes.

               Now the question arises, how do we get common salt?

               Common salt in fact is a compound of sodium and chlorine. It also contains several minerals such as iodine. One atom of sodium combines with one atom of chlorine and forms one molecule of sodium chloride.

               Since sea has an abundant quantity of salt, it remains the main source of its supply. To obtain it through artificial means, water is led into wide, shallow basins about 3 feet deep. In the first one the solid impurities like sand, mud and tiny living creatures get settled. Calcium sulphate is also separated from the water in this basin. The water then flows into a succession of basins and evaporates there. In the process, sodium chloride is deposited there. This is collected, dried, refined and purified.

               In cold countries, a different method is used for the extraction of salt. In this, sea water is allowed to freeze, since the ice from frozen sea water does not incorporate the molecules of salt. These accumulate in the unfrozen water under the ice and make it more salty. The floating ice is gradually removed and further frozen, until only a little highly saline water remains. This is collected and evaporated by means of artificial heat, and salt is collected.

               There are many salt deposits in the world. The salt formations of Kansas, Oklahoma, Texas and New Mexico in the U.S.A. cover an area of about 100,000 square miles and are the largest in the world.

               Common salt is basically used for flavouring and preserving food. 

               We all know that sea water is salty. It  contains many minerals which make it salty. Salinity of sea water varies a great deal in different parts of the ocean. On an average, there are 35 parts of salt to every 1000 parts of sea water. Now the question is whether it is possible to remove salt from the sea water and make it drinkable.

               There are several methods to make the sea water drinkable. One method is distillation. In this, sea water is boiled and the steam is condensed into water. Water gets vaporized leaving behind the salt. Water so obtained is fresh and good for drinking. For this purpose, nuclear energy or solar energy is used.

               In another method, electrical energy is used. Here, an electrical current is passed through the sea water. The electric current causes positive salt ions to flow in one direction and negative ions in the other. In fact, about 3.5 per cent of sea water consists of dissolved elements. These elements are sodium and chlorine which together form salt. On passing electricity, sodium ions move towards cathode and chlorine ions towards anode. This way, salt is removed from the water and water becomes worth drinking.

               In another method, some special types of membranes are used to purify water. There are thin membranes which let pure water through while blocking the flow of salts. Water filtered with these membranes becomes pure.

                By another method, the sea water is simply frozen. This process extracts salt from the water. After the salt has been separated from the ice, the ice is melted, giving fresh water. But this process is only for limited purposes.

               One of the best methods of obtaining fresh water is called multi-stage flash distillation. In it sea water vaporizes rapidly several times, each time in a higher vacuum and at a lower temperature.

               The world is now faced with an ever-increasing demand for fresh water.

               Scientists in many countries of the world are developing new methods for obtaining fresh water from the sea. In Israel, for example, and other oil-producing countries in Middle East, it has become worthwhile to build big plants to distill fresh water from the sea. However, due to high cost in processing, it is not still considered economically viable as an alternate source of fresh water. The research on the subject is still in experimental stage. 

               It is a well known fact that when resins are put in water they get swollen. This swelling takes place due to the entry of water through the membrane of the resins. Similarly, if grapes are put in sugar solution they shrink. Swelling of resins and shrinking of grapes take place due to a process known as osmosis. Do you know what this osmosis is?

               Osmosis is a process in which a solution of lower concentration passes into a solution of higher concentration through a semipermeable membrane. A semipermeable membrane is one that allows some, but not all, substances to pass through it. This contains very small pores. When resins are put into water, the covering acts as a semipermeable membrane. Water is less concentrated than the substance present inside the resins and so the water moves into the resins through its semipermeable membrane. Similarly, fluid from grapes moves out through the semipermeable membrane, as the concentration of sugar solution is more than that of the grapes. There is a tendency for solutions separated by a membrane to become equal in molecular concentration.

               In osmosis, the movement is always from a dilute solution into a solution of higher concentration. This reduces the concentration of the stronger solution. The rate of osmosis depends upon the comparative strengths of the two solutions. The greater the difference, the faster the rate of osmosis. This process continues until both solutions are of equal strength. When this equilibrium is reached, osmosis stops.

               Osmosis is an ongoing process among the living beings. The membranes of cells are semipermeable. Plants absorb water and dissolved minerals from the soil by osmosis; they use osmosis to move the water and dissolved minerals through the plant, cell by cell. Osmosis also maintains turgor pressure. Turgor pressure is the pressure of water on the cell. It gives the cell form and strength. When there is a decrease in turgor pressure, the plant will soon wilt and lose its regular stiffness.

               Osmosis allows the transfer of water and dissolved nutrients in the human body from the blood into the cells.

 

            Wax is an insoluble solid fatty substance that is widely used as a protective covering for different kinds of surfaces. It is also used for making candles and polishes. Waxed paper is an item of our daily use. Do you know how wax is made?

            Normally wax is solid at room temperature but softens and becomes sticky when heated. Many fruits and vegetables, and leaves of many plants have a thin protective coating of wax. It is useful in protection of organisms. Many animals also produce wax. We get wax in large quantities from minerals and petroleum. Nowadays synthetic methods have been developed for the manufacture of wax.

             Depending upon the source from which wax is obtained, we classify wax into four kinds: (i) mineral wax (ii) animal wax (iii) vegetable Wax and (iv) synthetic wax. Paraffin wax is a kind of mineral wax which is taken out of petroleum. This is quite hard in nature. Petroleum jelly is a kind of soft wax and is used for medicinal purposes. More than 90 percent of all commercial wax used today is petroleum wax. This is very useful because it is odourless, tasteless and chemically inactive.

            Animal wax, such as bees wax produced by bees, is used for making candles, cosmetics, polishes, crayons and artificial flowers. We get wool wax from wool-bearing animals and are called lanolin when purified. Lanolin is widely used for manufacture of moisturizer and skin creams.

            We get several kinds of wax from plants. Carnauba wax is obtained from the leaves of the carnauba palm trees of Brazil. This wax is hard and gives an excellent brightness when used as a floor and furniture polish. Candellilla wax comes from a plant of the same name that grows in Mexico and the South Western United States. It is a brown wax used in phonograph records, floor dressings and candles. Bay berry wax from the berries of this shrub is used for making candles.

            Synthetic waxes are chemical combinations of hydrogen, carbon, oxygen and sometimes chlorine. They are made according to different formulae to have definite properties.

 

                Ammonia gas is a colourless non-poisonous gas that has pungent smell and strong irritating effect on the eyes, nose, throat and lungs. It is highly soluble in water and a compound of nitrogen and hydrogen. One atom of nitrogen on combining with three atoms of hydrogen forms one molecule of ammonia. This gas can be liquefied by compressing or by cooling at -33°C. At normal temperature and pressure, 700 volumes of ammonia can dissolve in one volume of water. Its solution in water is basic in nature and is known as Ammonium Hydroxide.

               There are several methods of making ammonia gas. In the laboratory, this gas is prepared by heating a mixture of ammonium chloride and lime. On a large scale, this gas is manufactured by causing a chemical reaction between hydrogen and nitrogen. This method is called Haber’s Process. In this process one part of nitrogen and three parts of hydrogen are mixed and compressed to 500°C in the presence of iron which acts as a catalyst. Ammonia can also be obtained by distilling coal into coke and coal gas.

                Ammonia is very useful to us. It is used in the manufacture of many of its compounds and also for making nitric acid which is used to dissolve many dry cells. This is also used in the dyeing and printing industry.

                Ammonium sulphate is an important compound of ammonia. It is made from ammonia and sulphuric acid. It is used as a fertilizer because it provides nitrogen for the soil. Ammonium nitrate is used in fertilizers, explosives and for making nitrous oxide, also called, ‘Laughing Gas’.

               The ammonia used as a household cleaner is a strong solution of gas in water. It is also used as cooling agents in refrigerators.

 

               We know that light is a form of energy and it travels in the form of electromagnetic waves. These waves are made up of electrical and magnetic vectors which are perpendicular to each other and also to the direction of propagation. The electro-magnetic theory of light was propounded by a physicist Maxwell. This was a very comprehensive theory, but yet could not explain certain phenomena of physics.

               We know that red hot objects usually emit red light. The frequency of this light does not depend upon the substance which is being heated up but upon the temperature of the substance. Efforts were made to establish a relationship between temperature and frequency on the basis of electromagnetic theory. But, the theory failed to explain the frequencies of ultraviolet light. 

               However, this problem was solved in 1900 by a German physicist, Max Karl Planck. He suggested that light is emitted in bundles or packets instead of a steady stream. And this packet of light was called quantum. The contention put forth by Planck is now known as the Quantum Theory. According to this theory the energy of each quantum is proportional to its frequency.

               In 1905 Quantum Theory solved another problem of photoelectric effect. It enabled the famous German physicist, Albert Einstein to put forward his theory of photoelectric effect. He named the light quantum as photon.

                Later, Quantum Theory was used to explain many mysteries of atom. Today it has become possible to explain many effects of physics on the basis of quantum theory. Now physicists think of light as waves for some purposes and as quanta for other purposes. However, there is a highly respectable version of Quantum Theory developed recently by John Cramer, of University of Washington. His interpretation is simple and provides a new insight into the significance of the present research in this field.

               A battery is a device that produces electricity by chemical action. It contains more than one cell. Each cell produces its own current. Batteries with several cells are used to provide electricity for automobiles, heavy equipments, space crafts, submarines and emergency electric lights.

               The battery which is used in a car is called a storage or wet battery. Storage or wet battery like car battery has a greater capacity and produce more electricity in comparison to other batteries. It can be recharged again and again in order to use for a considerably longer period. The first such battery was invented in 1859 by a French physicist, Gaston Plante.

               Storage or accumulator batteries are of two types: acid accumulators and alkali accumulators. Lead-acid batteries consist of plastic or hard-rubber containers. These batteries are used in cars throughout the world. Each cell of this battery contains two sets of electrodes. The pairs are suspended in dilute sulphuric acid. One electrode is positive and the other negative. One electrode is made of spongy lead and the other of lead dioxide. The separator plates keep them apart. This cell requires distilled water. Such a cell has a potential difference of 2 volts and the cells are connected in series. Most car batteries have 6 cells, giving 12 volts in all.

               At the positive electrode, lead dioxide reacts with hydrogen and sulphate ions of sulphuric acid and forms lead sulphate and water. In this reaction, two electrons are obtained from the wires which balance the chemical reaction. At the negative electrode, lead reacts with sulphate ions and forms lead sulphate. This provides two electrons to the wire which maintains electrical balance. The net effect of this reaction is that electrons start flowing from the negative plate to the positive plate.

               When the lead of lead dioxide is over, the cell stops working. This cell can be re-charged by making the electricity flow from the negative to the positive plate. 

               Sugar making process was known in India as early as 3000 B.C. In Sanskrit, the word sugar is Sakkara. Gaura, another old Indian word for sugar was derived from the name of Gur for domestic non-purified sugar.

               Do you know how is sugar made by modern techniques? Before that it is worthwhile to know how sugarcanes and beets were first used to make sugar. Sugarcane is believed to have originated in Solomon Islands in South Pacific. The methods of sugarcane growing were passed from India to Indochina (modern Vietnam and Cambodia) and from Arabian countries to Europe. It is said that in 1493, Columbus brought sugarcane to the New World. Similarly beet grew wild in parts of Asia and also cultivated quite early in some part of Europe. In 1747, Andreas Marggraf, a German chemist proved that beet-roots contained sugar that can be extracted in crystalline form to make sugar. 

 

 

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               Usually when solids are heated they melt and become liquid. Then, on further heating the liquid boils to form a gas. When we keep a piece of ice in a dish, it melts and the water so formed evaporates after sometime. However, there are some substances which on heating directly turn into gases from solids. Camphor, iodine crystals and solid carbon-dioxide are such substances. Such substances are called sublimatory substances and this process of conversion is known as sublimation. Do you know why does this happen?

               As we know, all substances are made up of atoms and molecules. These particles are held together by a force of attraction. If the force of attraction is weak, the particles can be separated easily. In a block of ice, the force of attraction is quite weak. With a small amount of heat the ice melts into water and further heat separates the particles of water further to form water vapours. Similarly the camphor molecules are held together by weak forces, even weaker than ice molecules, and simply evaporate on heating without melting.

               A piece of camphor gives off a strong smell. It means that even at a moderate temperature, the molecules of camphor escape and spread everywhere. The atmospheric heat is enough to separate its molecules. At 179°C camphor melts to form a liquid but the moment it melts it catches fire and starts burning. However, if we remove all oxygen from its surroundings then it melts. Now camphor can’t burn, because there will be no oxygen around it.

               If you burn camphor in an open dish, you can see the burning piece of camphor floating on a colourless liquid. This is the liquid camphor. Camphor is used in the manufacture of celluloid and also in many other industries.

 

              We all know that a motorcycle is a two-wheel vehicle. The first motorcycle was made in Germany in 1885 by Gottlieb Daimler. It was the first wooden framed motorized bicycle. However, this industry didn’t come into its own until the end of the nineteenth century. The early motorcycles were simply modified bicycles with powered engines. Soon frames were designed to suit motorcycles to make it a more acceptable vehicle. Do you know how does a motorcycle run?

               A motorcycle works on a principle similar to most other vehicles. It has an internal combustion engine. This may be a two or four stroke petrol engine or rotary wankel type, either air cooled or water cooled. In an internal combustion engine, fuel is mixed with air in a cylinder. The fuel is ignited by a spark. As the fuel burns, it produces hot gases in a large quantity. These gases push a piston along the cylinder. And the piston provides the power for the wheels. Most motorcycles have one or two cylinders. Racing motorcycles sometimes have more than two cylinders. 

               Like many other automobiles, motorcycles have a device called ‘clutch’. This is operated by a hand lever. It disconnects the engine from the gear box. It is used when the rider is starting, stopping or changing the gear. Most motorcycles have three or four gears. The gears are foot-operated. It is started by pushing down a kick. It turns the engine and starts its firing. The clutch lever is on one side of the handle bars. On the other side is a lever for the front brake. The rear brake is operated by a foot pedal. Motorcycles are fitted with either drum or disc brakes. The drum brake consists of a brake drum built into the wheel hub and a pair of brake shoes lined with an asbestos-based material. These shoes press against the inside of the drum when the brake is applied. The disc brake is basically a steel disc mounted on the wheel hub with a pair of pads.

               The speed of the engine is controlled by a twist grip control on the right hand side of the handle bars which are connected to the carburettor by a cable. Most of the modern motorcycle frames are made of steel tubing with the engine mounted on twin tubes. These tubes form the bottom section of the frame. Suspension is provided for both wheels to give a greater comfort to the rider. The hydraulic damper units or shock absorbers regulate the upward and downward suspension. These shock absorbers provide protection against the bumps on the road. If no shock absorbers were fitted, the wheel bounce would make it inconvenient to drive a motorcycle as the driver will lose control over the vehicle. The dampers work as a check against oscillations on rough and uneven roads. In a modern motor cycle sophisticated devices are introduced to make it pollution free and lesser absorber of fuel with better average of mileage. 

               Sometimes, when we visit to a hairdresser’s shop for cutting or shaping our hair we find them often using an appliance for drying hair. Now, how does this hair drier work? We are aware of the fact that the electric heater, electric bulb, immersion heater, etc. are the domestic appliances which work on the heating effects of electric currents. Hair drier also works on the same principle.

               A hair drier consists of a cover usually made of plastic. It is shaped like a pistol. Inside this plastic cover, a coil of nichrome wire is fitted. The coil gets heated up when electric current is passed through it. This heating element is made from special resistance materials. At the back of this coil, a very small electric fan is fitted. It has two switches which make the current flow through the fan and the nichrome coil. When one switch is put on, the electric fan starts running and the cold air comes out from the plastic cover. When the second switch is put on, the coil gets heated up and as a result the wind blown by the fan also gets heated. The fan blows moisture laden air away from hairs continuously, replacing with fresh dry air. The machine is widely used in some circles as an essential house-hold item.

               This apparatus is not only used for drying hair but also for drying in the research laboratories in a number of experiments where drying process is necessary.

               We all know that rapid industrialization and modernization of technology from field to factories, from laboratory experiments to space exploration are closely linked with energy generation. But during the last century man’s activities, principally concerning energy development, have caused fossil burning wantonly. This has raised the atmospheric concentration of Greenhouse gases leading to an increase in the average global temperature which is called “Global warming”.

               What actually is the “Greenhouse effect”? Our earth reflects a lot of energy back into the atmosphere. But presence of heavy carbon-dioxide in the atmosphere prevents some of this heat escaping just as a glass or plastic sheet stops escaping heat from the so called “Greenhouse” used to protect growing plants. The main Greenhouse gas is carbon-dioxide. The source of this gas is from fossil fuel combustion like coal, petroleum and natural gas. Methane, Chlorofluorocarbon (CFCs) and Nitrous oxide are among the other Green house gases. The sources of such gases range from Bio-mass burning, fumes emitted from refrigeration and air conditioning plants (Freon gas), industrial fumes and enteric fermentation of cattle, insects and different crops.

               Scientists believe that earth’s temperature will rise markedly in next 50 years. Between the present time to 2025 AD, it may rise by 1°C and further by 3°C during 2025-2100 AD. This would alter significantly the earth’s ecological balance, its normal cyclic seasons, melting of polar ice caps and the ultimate rise in sea level submerging many land areas. Widespread flooding in coastal regions all over the world will occur and large part of world’s civilization may disappear beneath the sea.

               Scientists are engaged in search of ways and means to combat this impending danger under the guidance of the Paris based International Council of Scientific Unions (ICSU).