Why do the lips of smokers turns into Black

The lips of smokers turn Black. 

Excessive cigarette smoking leads to blackened lips. It is tobacco, the main constituent of a cigarette, which contributes to the blackening of lips. Tobacco is prepared by drying the leaves of the nicotine plant. The leaves of the plant contain an excessive amount of an alkaloid which is known as nicotine. An alkaloid is formed by the decomposition of proteins and contains compounds of nitrogen. It is generally a waste product.

Nicotine contains a fluid called nicotine gel, which has mercury in it and is slightly yellow.

When a cigarette is lighted and brought in contact with the lips, the nicotine in the tobacco burns and turns into a black semisolid substance that precipitates on the lips, turning them black.

Simultaneously, when the cigarette is lighted, its filter, which is composed of cotton fibers, also gets heated. it is this heat that destroys the outer dead layer of the lips which are composed of dead squamous epithelial cells.

Thus, the deposition of nicotine gel and the destruction of the outer layer of lips lead to their blackening, something that easily identifies a smoker. 

Why do Hiccups stop after Drinking lots of Water?

Hiccups are caused by a sudden intake of air through the larynx or voice box. As the air forcibly strikes the closed epiglottis (a movable fleshy cap that keeps food from getting into the air passage), causes a movement in the vocal cord. This results in the 'hic' sound.

However, this involuntary surge of air is caused by a spasm in the diaphragm, which is a large, powerful dome-shaped muscle that lies at the base of the chest cavity. It contracts and relaxes to draw air in and out of the lungs.

Normally, the contractions of the diaphragm are rhythmic and gentle, but the irritation of organs near the diaphragm may result in its sudden contraction. This pulls air into the lungs through the larynx, which is flanked by the vocal cords and topped by the epiglottis.

As the epiglottis closes over the larynx, the air hits the closed epiglottis and hiccups occur. Hiccups can be stopped by interrupting the rhythm of the spasm of the diaphragm. Drinking lots of water causes swelling of the stomach which in turn puts pressure on the diaphragm and stops its spasmodic rhythm, thereby stopping hiccups.