Why is salt soluble in water but not in oil?
Why is difficult to tie a knot in a silk lace?
A knot in a lace is held together by the friction between the surfaces of the lace. Greater the friction more stable the knot will be. Since there is enough friction between cotton fibres in a lace made of cotton, it is quite easy to tie a knot. But silk being a smooth fibre, a knot tied with a silk lace becomes loose and opens up easily due to lack of friction between the fibres.
Why do bubbles show rainbow colours?
Why do coloured soaps produce white bubbles?
Why does ice melt when subjected to pressure?
Why does the surface of boiling milk rise?
Milk is a fine suspension of fat and protein globules in a watery liquid containing milk sugar (lactose) and other dissolved substances. Normally the fat is dispersed uniformly in the form of fine droplets and hence remains as an emulsion. But when milk is heated these fine droplets tend to raise up and at temperature of about form a thick layer of cream on the surface. When milk comes to boiling, bubbles of steam formed at the bottom of the vessel rise up and force the thick creamy layer upwards causing the milk to spill.
Why doesn’t soap form lather in hard water?
Why do synthetic fabrics dry so quickly?
Why does food feel tasteless when we have a cold?
There is a close link between the sense of taste and the sense of smell. Much of what we think of as taste has a big smell component. The taste buds in the tongue monitor relatively crude sensation of the four basic tastes – sweet, salty, sour and bitter. Faint vapours of whatever we eat drift into the nasal cavity where the smell receptors add more detail to the information given by the taste buds.
When we have a cold our nose becomes blocked and the sensation of smell ceases. The gas and vapours from the food cannot be sensed by the smell receptors; consequently we cannot perceive the smell or aroma of the food, which in turn makes the food appear tasteless.
Why do cut onions bring tears?
Tears produced by the tear glands keep the eyes moist and are normally drained off through the nose. Onions contain a number of water soluble volatile substances containing sulfur. On cutting the onion these substances quickly spread into the air and cause irritation in eyes. The tear glands start secreting more and more tears to wash out the irritants. The tears are produced so rapidly that they cannot be drained out through nose and so run down the eyes.
Why is sea water salty?
Sea water is salty because it contains many dissolved salts, mostly sodium chloride with small proportions of potassium, magnesium, calcium and carbonates. The salt comes mainly with river water that flows through rocks eroded by frost and rain. The gradual wearing a way of mountains releases chemicals which are carried down by rivers to the ocean as dissolved salts. Some salt also enters sea water from the rocks beneath the sea bed. The river water carrying the salts to the sea does not taste salty because the salts are present in extremely small concentration. Whereas in the case of the oceans, water is continuously evaporating even as more and more salt continues to be added with river water. This, over millions of years has led to the high concentration of dissolved salts in sea water.
Why is there a scent after it rains on parched soil?
The peculiar smell is produced by the soil inhabiting bacteria called streptomycetes. Streptomycetes are abundant in dry warm soil – a million of them are present in a pinch of soil. They release compounds such as geosmin and 2-methyl isoborneol, which vapourize easily, when wetted by rain water after a dry spell. That is why we get the musty odour only after the first rain of the rainy season. The smell can be detected in a newly ploughed field also.
Why do the dry beds of ponds and lakes crack?
The bottom of lakes and ponds, which usually hold still water, is usually covered with sediments formed of clay material. Clay contains chemical substances such as sodium bentonite which have the property of expanding when wet. The loss of moisture, therefore, makes this layer of clay shrink resulting in cracks on its surface. Thus, in summers when lakes and ponds go dry, the surface of their beds shows large cracks.
What are the different types of handshakes?
When you meet another person, or are introduced to him, it is polite to say ‘Namaste’ with folded hands, or extend your hand for a handshake. The handshake is the universal form of greeting in the West. However, even this simple gesture varies from country to country.
The American style handshake has a firm grip along with two quick pumps, eye contact and a smile. Variations in handshakes are based on cultural differences, not on personality or values. The Japanese give a light handshake. Germans offer a firm handshake with one pump, and the French grip is light with a quick pump. Middle Eastern people will continue shaking your hand throughout the greeting. Don’t be surprised if you are occasionally met with a kiss, a hug, or a bow somewhere along the way!