How chlorofluorocarbons (CFCs) causes degradation or ozone depletion in stratosphere ?

How chlorofluorocarbons (CFCs) causes degradation or ozone depletion in stratosphere ?  

Ozone gas is continuously formed by the action of UV rays on molecular oxygen, and also degraded into molecular oxygen in the stratosphere. There should be a balance between production and degradation of ozone in the stratosphere. But the balance has been disrupted due to enhancement of ozone degradation by chlorofluorocarbons (CFCs). CFCs find wide use as refrigerants. CFCs discharged in the lower part of atmosphere move upward and reach stratosphere. In stratosphere, UV rays act on them releasing Cl atoms. Cl degrades ozone releasing molecular oxygen, with these atoms acting merely as catalysts; Cl atoms are not consumed in the reaction. Hence, whatever CFCs are added to the stratosphere, they have permanent and continuing effects on Ozone.

 

Why the soap bubble or petrol on water give a color full spectrum ?

Why the soap bubble or petrol on water give a color full spectrum ?

Soap bubble or petrol on water give a color full spectrum because of interference of light. Each color of light has a different wavelength hence a disparity in the path of light will cause constructive interference of certain colors whereas other color will not be observed because of destructive interference. Because the oil film gradually thins from its center to its periphery, different bands of the oil slick produce different colors.

What is allergy ? How it occured.

  What is allergy ? How it occured.

 Allergy is due to pollen, mites, etc., which are different in different places. The exaggerated response of the immune system to certain antigens present in the environment is called allergy. The substances to which such an immune response is produced are called allergens. The antibodies produced to these are of IgE type. Common examples of allergens are mites in dust, pollens, animal dander, etc. Symptoms of allergic reactions include sneezing, watery eyes, running nose and difficulty in breathing. Allergy is due to the release of chemicals like histamine and serotonin from the mast cells.

Why the dough ,which is used for making foods such as dosa and idli puffed-up appearance ?

Why the dough, which is used for making foods such as dosa and idli puffed-up appearance ?

The dough, which is used for making foods such as dosa and idli is fermented by bacteria. The puffed-up appearance of dough is due to the production of  CO2 gas.  

Why an ice float on water ?

 Why an ice float on water ? 

The crystalline form of water is ice. At atmospheric pressure ice crystallises in the hexagonal form, but at very low temperatures it condenses to cubic form. Density of ice is less than that of water. Therefore, an ice cube floats on water. And  have low density than that of water and have open cage like structure.

Why presence or absence of hymen is not a reliable indicator of virginity or sexual experience ?

Why presence or absence of hymen is not a reliable indicator of virginity or sexual experience ?

The female external genitalia include mons pubis, labia majora, labia minora, hymen and clitoris . Mons pubis is a cushion of fatty tissue covered by skin and pubic hair. The labia majora are fleshy folds of tissue, which extend down from the mons pubis and surround the vaginal opening. The labia minora are paired folds of tissue under the labia majora. The opening of the vagina is often covered partially by a membrane called hymen. The clitoris is a tiny finger-like structure which lies at the upper junction of the two labia minora above the urethral opening.  The hymen is often torn during the first coitus (intercourse). However, it can also be broken by a sudden fall or jolt, insertion of a vaginal tampon, active participation in some sports like horseback riding, cycling, etc. In some women the hymen persists even after coitus. In fact, the presence or absence of hymen is not a reliable indicator of                                                                    virginity or sexual experience.

Why mother’s milk is considered very essential for the new- born infant?

Why breast-feeding during the initial period of infant growth is recommended by doctors or important for bringing up a healthy baby ? or why mother’s milk is considered very essential for the new- born infant?

The mammary glands of the female undergo differentiation during pregnancy and starts producing milk towards the end of pregnancy by the process called lactation. This helps the mother in feeding the new- born. The milk produced during the initial few days of lactation is called colostrum which contains (The yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant. The foetus also receives some antibodies from their mother, through the placenta during pregnancy. ) several antibodies absolutely essential to develop resistance for the new-born babies. 

How microorganisms like lactobacillus is important in curdling of a milk and improve its nutritional value ?

How microorganisms like lactobacillus is important in curdling of a milk and improve its nutritional value ? 

Micro-organisms such as Lactobacillus are called lactic acid bacteria (LAB) grow in milk and convert it to curd. During growth, the LAB produce acids that coagulate and partially digest the milk proteins. A small amount of curd added to the fresh milk as inoculum or starter contain millions of LAB, which at suitable temperatures multiply, thus converting milk to curd, which also improves its nutritional quality by increasing vitamin B12.

Why small drops of mercury form spherical bead instead of spreading on the surface.

Why small drops of mercury form spherical bead instead of spreading on the surface. Why do particles of soil at the bottom of river remain separated but they stick together when taken out ? Why does a liquid rise (or fall) in a thin capillary as soon as the capillary touches the surface of the liquid ?
 

All these phenomena are caused due to the characteristic property of liquids called surface tension.  A molecule in the bulk of liquid experiences equal intermolecular forces from all sides. The molecule, therefore does not experience any net force. But for the molecule on the surface of liquid, net attractive force is towards the interior of the liquid due to the molecules below it. Since there are no molecules above it. Liquids tend to minimize their surface area. The molecules on the surface experience a net downward force and have more energy than the molecules in the bulk, which do not experience any net force. Therefore, liquids tend to have minimum number of molecules at their surface. If surface of the liquid is increased by pulling a molecule from the bulk, attractive forces will have to be overcome. This will require expenditure of energy. 

Why blood group o is called 'universal donors' ?

Why blood group o is called 'universal donors' ?

Blood group o is called 'universal donors' because person with blood group o has no antigen on RBCs but antibodies in plasma has anti-A and anti-B.

Why graphite in the pencil are conductor of electricity ?

Why graphite in the pencil are conductor of electricity ?

Graphite in the pencil are conductor of electricity because each carbon atom is bounded to other carbon atom in the same plane giving a hexagonal arrangement. One of these bonds is a double bond and thus the valency of carbon is satisfied. Having hexagonal structure one layer is placed over other this cause the movement of electron freely ,so it conduct electricity.