A Guide To The Scientific Knowledge Of Things Familiar Part 7

A. Water is cold, and sulphuric acid is cold; but if these two _cold_ liquids be mixed together, they will produce _boiling heat_.

Q. _Why will COLD WATER, mixed with SULPHURIC ACID, produce heat?_

A. Because water (being _lighter_ than sulphuric acid), is _condensed_ by the heavier liquid; and its heat is _squeezed out_, as water from a sponge.

Q. _Why does COLD WATER, poured on LIME, make it intensely HOT?_

A. The heat is evolved by the chemical action, produced by the cold water combining with the lime.

Q. _Where does the heat come from?_

A. It was in the water and lime before; but was in a _latent state_.

Q. _Was there heat in the cold water and lime, before they were mixed together?_

A. Yes. _All_ bodies contain heat; the coldest ice, as well as the hottest fire.

Q. _Is there HEAT even in ICE?_

A. Yes. But it is _latent_, (i. e. not perceptible to our senses).[4]

[4] Latent, from the Latin word, Lateo, (to lie hid.)

Q. _How do you know there is heat, if you cannot perceive it?_

A. Thus:--Ice is 32 by the thermometer; but if ice be _melted_ over a fire, (though 140 of heat are thus absorbed,) it will feel no _hotter_ than it was before. (_i. e. it will be only 32, and not 172_)[5].

[5] 32, i. e. 32 degrees; 140, i. e. 140 degrees, &c.

Q. _What becomes of the 140, which went into the ice to melt it?_

A. It is hidden in the water; or (to speak more scientifically) it is stored up in a _latent state_.

Q. _How much heat may be thus secreted or made latent?_

A. _All_ things contain a vast quant.i.ty of latent heat; but, as much as 1140 of heat may remain latent in _water_.

Q. _How can 1140 of heat be added to water, without being perceptible to our feelings?_

A. 1st--140 of heat are hidden in the water, when ice is melted by the sun or fire.

2ndly--1000 more of heat are secreted, when water is converted into steam. Thus, before ice is converted into steam, 1140 of heat become _latent_.[6]

[6] Thus, one pint of boiling water, (212 according to the thermometer,) will make 1800 pints of steam; but the steam is no hotter to the touch than boiling water, both are 212: therefore, when water is converted into steam, 1000 of heat become latent. Hence, before ice is converted to steam, it must contain 1140 of latent heat.

Q. _Can we be made to FEEL the heat of ICE or snow?_

A. Yes. Into a pint of snow put half as much salt; then plunge your hand into the liquid; and it will feel so intensely cold, that the snow itself will seem quite _warm_ in comparison to it.

Q. _Is SALT and SNOW really COLDER than snow?_

A. Yes, many degrees; and by dipping your hand into the mixture _first_, and into snow _afterwards_, the mere snow will seem to be comparatively warm.

Q. _What is FIRE?_

A. Combustion is another instance of heat, arising from chemical action.

Q. _What two things are essential to produce combustion?_

A. Fuel and air.

Q. _What are the elements of fuel?_

A. As bread is a compound of flour, yeast, and salt; so fuel is a compound of hydrogen and carbon.

Q. _What are the ELEMENTS of atmospheric AIR?_

A. The air is a compound of oxygen and nitrogen _mixed_ together; in the proportion of five gallons of nitrogen, to one of oxygen.

Q. _What is CARBON?_

A. The solid part of fuel. It abounds also in all animal bodies, earths, and minerals.

Q. _Mention some different SPECIES of CARBON._

A. Common charcoal, lamp-black, c.o.ke, black lead, and the diamond, are all varieties of carbon.

Q. _What is HYDROGEN?_

A. An inflammable gas. The gas used in our streets, is only the hydrogen gas _driven out of coals by heat_.