Category Chemistry

What is Osmosis?

               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.

 

How is wax made?

            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.

 

What is Greenhouse Effect?

               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).

 

What is a Chemical Warfare?

          A chemical warfare involves the use of chemical substances to kill or cause physical harm to the enemy or to destroy its food supply. The intention behind using these weapons is to destroy life without damaging any property. In the ethics of modern warfare use of chemical substances are prohibited.

          This type of warfare has continued over the ages — in fact throughout the human history. There is evidence to prove that the ancient Greek warriors had developed chemical fire bombs and used them against the enemies. In recent times, chemical warfare found an extensive use in World War I (1914-1918). In January 1915, the Germans used chlorine gas against the Russians in Poland — although too little effect. But on 22 April 1915, using similar weapons they scored a tactical victory against the French and the British in Flanders that went beyond their expectations. The chlorine gas affected the lungs of soldiers causing choking and making it difficult for them to breathe. It, in fact, disabled so many soldiers that the Germans later devoted much more time for research on harmful gases.

          In 1917 the Germans introduced the mustard gas. Its special feature is that unlike other gases it directly affects the skin and is absorbed through it thus rendering the gas masks useless. It causes blisters on the skin and irritation to the lungs. Thus in the war more soldiers died from this gas than any other gas.

          After World War I, a major breakthrough was achieved by Germany in the development of nerve gases. They were far more toxic than the gases used in World War I, but were never used. In fact the nerve gases interfere with the normal activity of the nerve cells, and can cause convulsions, vomiting and death. Many such gases are tasteless, odourless and colourless.

          Many other such poisonous gases have reportedly been produced in various countries. These also include blood gases which interfere with the normal functioning of the blood and utilization of oxygen by the body tissues.

          Other gases, such as tear gas, have a temporary effect. Tear gas causes excess tears, irritation the nose, mouth and eyes and violent coughing. It is used by police in controlling crowds and riots, but has been used occasionally by military also.

         Gas warfare is potentially so harmful that there have been international agreements to prevent its use. Hence the use of harmful gases has been kept to the minimum since World War I. However, nerve gases were said to have been used in the gulf war during 1991.

          Some chemicals are used to kill plants to destroy the food reserve. These defoliants were widely used in the Korean and Vietnamese conflicts. 

What are solar flares?

          A solar flare is defined as a sudden intense brightening of a small part of the sun’s chromosphere near a sunspot group. The brightness of the flare may be five times that of the associated plage or facula. The flare develops in a matter of a few minutes and may last for several hours. In a large solar flare, tremendous energy to the extent of ergs is released.

          Solar flares occur only as a result of sunspot activity. Practically all sunspots produce some flares but certain spots are much more active. Their source of energy is the magnetic fields surrounding the sunspots.

          Such flares are rarely seen in white light because they are an atmospheric phenomenon, with such low density that they’re transparent. On the other hand, their temperature is so high that in the ultraviolet zone, they may equal the intensity of the entire Sun. However, because the flares are most easily observed in Ha (H-alpha) and because the Ha brightening is an extremely accurate indicator, they can be studied well.

          Solar flares emit ultraviolet radiations and X-rays. They also emit great amount of energetic particles and cosmic rays. The particles travel much slower than the light of the flare and reach the vicinity of Earth a day or two later. They pose a potential radiation hazard to human beings in space. During solar flares, jets of particles known as the solar wind, and strong radio frequency electromagnetic radiations are emitted which disrupt radio communications and cause auroras.

          Flares also produce intense streams of electrons. These travel at about one third of the speed of light. 

What is a poison?

            A poison is a toxic substance that is damaging to life. When taken in excess, it causes irritation, soreness, roughness or redness, vomiting, nausea etc. Sometimes it can cause internal injury, sickness or even death. Poisons may be natural substances produced by living things like animals or plants. They can also be artificially made from different chemicals. Some minerals are also poisonous.

            There are different types of poisons: corrosive, irritant, systematic, gas poisons and food poisons. 

            The corrosive poisons kill the living tissues. In case of human beings it may damage the lining of the mouth or throat. Sodium hydroxide, some acids and phenols, are examples of corrosive poisons.

           

            The irritant poisons cause swelling and soreness of the muscous membranes. They may also damage the stomach, intestines or nerve centres. Some medicines, when taken in excess dosage, can act as irritant poisons. Some other can, make the body bleed inside. 

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