Category Chemistry

What is Biodegradation?

This is the process by which living organisms breakdown matter into its simpler constituents and thus recycle nutrients. All natural decay processes such as rotting of wood are examples of biodegradation. The life forms responsible for the process are called decomposers and they form a vast, complex community of soil organisms such as microbes and fungi. All such matter on which they can act is termed biodegradable to distinguish it from non-biodegradable matter or such matter which is not broken down by biological agents. While all organic matter is biodegradable, certain decomposers can attack even metal, glass and plastic. The widespread use of non-biodegradable material such as the various types of plastics is a cause for alarm because when discarded they do not decompose easily but remain in the environment as pollutants. Efforts are underway to develop biodegradable plastics which will be more environments friendly.

What is Detergents?

Detergents are synthetic chemical salts which change the surface property of water and which are used as cleaning agents. Detergents contain one or more chemicals called surfactants, which reduce the surface tension of water by weakening the forces between water molecules. This enhances the cleaning action of water. A detergent molecule has two different parts. One part is hydrophilic (water-loving head) while the other is hydrophobic (water-hating tail). When soiled clothes are put in a detergent solution, water-loving head remains in water while the tail attaches to the grease or oil holding the dirt particles on the soiled material. Rubbing helps in breaking up the dirt. In this way the dirt particles are dislodged from the surface of the material and drawn into the wash water. After the dirt particles are suspended in water, a thin layer of surfactant remains around the particles keeping them separated. This prevents the dirt from settling on the washed material again. This is how detergents help in cleaning.

The common soap (sodium salt of fatty acid) is one of the oldest detergents but it is relatively weak. Synthetic detergents are stronger than soap and give lather even in hard water. 

What is Dialysis?

Dialysis is a process of separating dissolved substances from a solution using a semi-permeable membrane which allows only some dissolved substances to pass through. Many substances such as cell walls and cellophane act as semi-permeable membranes.

Dialysis is used to remove waste-products from the blood of patients with impaired kidney function. Accumulation of waste products especially urea, in the blood can prove fatal.

Dialysis of blood is carried out using a dialysis machine. Blood drawn from the artery in the forearm of the patient is passed through a semi-permeable membrane. The tubing is placed in a solution called dialysis fluid. Since the blood has a high concentration of impurities compared to the dialysis fluid, a concentration gradient builds up. This results in a flow of soluble impurities from the blood into the dialysis fluid. This continues till the concentrations on each side of the membrane are balanced. To prevent clotting of blood in the dialysis machine, the anti-clotting substance heparin is used.

 

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What is Atomic dock?

Atomic clock is a device for measuring time. It makes precise measurements of time. It makes use of the vibration of atoms or molecules, instead of quartz crystals or a coiled spring which are used in quartz and mechanical watches respectively, to measure time.

The most commonly used atoms and molecules in atomic clocks include caesium atoms, hydrogen atoms and molecules of ammonia gas. Atomic clocks based on rubidium atoms instead of caesium are now in use. Some atomic clocks gain or lose no more than a second in 200,000 years. These are used to keep time in laboratories and observatories. 

What is Amniocentesis?

It is a diagnostic technique to check for genetic abnormalities in unborn babies. The test involves taking a sample of the amniotic fluid which surrounds the growing baby inside the womb. It is usually done about the 16th week of pregnancy as by this stage there is enough amniotic fluid to allow the test to be carried out and enough time to terminate the pregnancy in case genetic abnormalities are detected. This can help prevent later suffering of the baby and the family.

For obtaining a sample a hollow needle is carefully inserted under local anaesthesia through the expectant mother’s abdomen. The amount of fluid withdrawn is only about 20 ml. This fluid contains cells from the developing baby. Chemical and microscopic examinations of these cells can provide invaluable information, revealing the presence or absence of genetic disorders which cannot be detected otherwise.

The chromosome analysis of the cells in the amniotic fluid can also reveal the sex of the baby.

What is Allergy?

Allergy is a state of hypersensitivity acquired through the exposure to a particular substance, called allergen. Spores, pollen, cat’s hair and proteins of egg, milk, and fish are some common allergens. The most common allergen is the house-dust mite.

Usually only parts of the body which are exposed to allergens show signs of allergy in the form of rashes or weals. However, if an allergen gets into the blood stream, it can cause reactions almost anywhere in the body.

Practically all allergies are caused by an over-reaction of the body’s defence mechanism when white blood cells react with allergens considering them as dangerous infectious organisms, it leads to allergy. Under normal conditions, the white blood cells (lymphocytes) on coming in contact with foreign substances like bacteria, viruses and proteinaceous matter produce what are called antibodies. The antibodies combine with the foreign substance and neutralize it. But when an antibody is formed against a harmless protein it attaches itself to mast cells which contain chemical— histamine. When the particular protein enters the body again, histamine is released. Due to the action of histamine blood capillaries are dilated, their walls become leaky and fluid from the blood comes out in the nearby tissues and they swell. The characteristic redness and itching in an allergy is due to dilation of blood capillaries.