Part 52 (1/2)
Q. _Does BOILING water get hotter by being KEPT on the FIRE?_
A. No; not if the steam be suffered to escape.
Q. _Why does not boiling water get HOTTER, if the steam be suffered to ESCAPE?_
A. Because _as fast as the water boils_, it is converted into _steam_; and the steam _carries away_ the additional heat, as fast as it is communicated.
Q. _Is STEAM visible or INVISIBLE?_
A. Steam is _invisible_; but when it comes in contact with the air (being _condensed into small drops_) it instantly becomes visible.
Q. _How do you know that STEAM is INVISIBLE?_
A. If you look at the spout of a boiling kettle, you will find that the steam (which issues from the spout) is always invisible _for about half an inch_; after which, _it becomes visible_.
Q. _Why is the steam INVISIBLE for only HALF AN INCH, and not either all INVISIBLE or all VISIBLE?_
A. The air is not able to condense the steam as it first issues from the spout, but when it _spreads_ and comes in contact with a larger volume of air, the _invisible steam_ is readily condensed into _visible drops_.
Q. _Why is our BREATH VISIBLE in winter-time?_
A. Because _it is condensed by the cold air_ into small drops, which are visible to the eye.
Q. _Why do STEAM-ENGINES sometimes BURST?_
A. Steam is very _elastic_; and this elasticity increases in a greater proportion than the heat which produces it; unless, therefore, some _vent_ be freely allowed, the steam heaves and swells, till it bursts the vessel which confined it.
Q. _What BECOMES of the steam, after it has been condensed?_
A. It is _dissolved by the air_, and forms a part of its invisible vapour.
Q. _Is AIR a good CONDUCTOR?_
A. No; _air is a very bad conductor_, and is heated (like water) _by convection_.
Q. _How is a ROOM WARMED by a STOVE?_
A. The air _nearest the fire_ is made hot _first_; _the cold air descends_, is heated also, and rises in turn; and this goes on, _till all the air of the room is warmed_.
Q. _Why are FIRES placed on the FLOOR of a room, and not towards the CEILING?_