3.Why do acids cause burn?

.acStrong acids such as concentrated sulfuric acid, hydrochloric acids or nitric acid are very
corrosive and can cause severe burns if they fall on our body.Acids can absorb water and bring
about a high temperature . All living cells contain water. Acid that fall on the skin absorbs
this water and produces heat, thus causing burns.

The first aid for an acid burn is to keep the affected part under water . Then you have
to wash the burnt areas with a solution of ammonia. This alkaline solution will nutralise the
acid.
However, not all acids are dangerous. Since acids are dangerous to living things,they
are used as preservatives to kill bacteria. Vinegar (Ethanoic acid) is widely used for pickle
making. This acid is a weak acid.

2.Why do we sleep?

We feel sleepy when we are tired after work.At night we feel sleepy. Why does one sleep?
It is the rest acquired through sleep that makes us energetic. Sleep is essential to remove
fatigue and to maintain health.
Numerous studies are being done on sleep. the brain controls all the functions of the
body. it has been concluded that the part called cerebellum in the brain controls sleep.
when we work for the whole day,the quantity of of calcium increases our blood. Sleep is
essential to reduce the quantity of calcium. It is the brain which gives the instuction to sleep.
When calcium was directly injected into the brain of animals, they soon fell down
sleeping. But when calcium was injected to blood they did not sleep, Thus, it has been
concluded that it is not only the quantity of calcium but something else is also the cause of
sleep. Research is progressing. Let us wait for the results.

1.What is Raman effect ?

Light is scattered by several substances.The natureof the scattered light was analysed by Loard Raleigh and to explain the phenomenon he developed the theory of 'elastic scattering of light'.in this theory is no provision for achange in the frequency of the light wave due to scattering. A.H. Compton while studying the scattering of X-rays by electron found a change in the frequency of elecron scattered. C.V.Raman,(1888-1970) who was working at the laborataries of the Indian Association for the Cultivation of science, Culcutta studied the light scattering by molecules. Although the possibility of a change in frequencies of light waves due to scattering was predicted by Heisenberg and Smackal,most scientists held the view that there is only a remote possibility of anyone detecting such a change. Raman succeeded in detecting the phynomenon,with the help of asimple apparatus,and this became famous as"Raman Effect".Raman was awarded Nobel Prize in 1930 for his discovey.