  Q. What is ice? A. Frozen Water. When the air is reduced to 32 degrees of heat, water will no longer remain in a fluid state. Q. Why is solid ice lighter than water? A. Because water expands by freezing; and as the bulk is increased, the gravity must be less. Nine cubic inches of water become ten when frozen. Q. Why do ewers break in a frosty night? A. Because the water in them freezes; and as the water is expanded by frost, it bursts the ewers to make room for its increased volume. Q. Why does it not expand upwards (like boiling water), and run over? A. Because the surface is first frozen, and the frozen surface acts as a plug, which is more difficult to burst than the earthen ewer itself. Q. Why do tiles, stones, and rocks often split in winter? A. Because the moisture (which they imbibed) freezes, and by its expansion splits the solid mass. Q. In winter time, foot-marks and wheel-ruts are often covered with an icy net-work, through the interstices of which the soil is clearly seen,—Why does the water freeze in net-work? A. The water in these hollows froze first at the sides of the foot-prints: other crystals gradually shot across the water, and would have covered the whole surface, had not the earth absorbed the water before it had time to freeze. Q. In winter time these foot-marks and wheel-ruts are sometimes covered with a perfect sheet of ice, and not an icy net-work,—Why is this? A. The air being colder and the earth harder (than in the former case), the entire surface of the foot-print is frozen over, before the earth can draw the water in. Q. Why is not the ice solid in these ruts?—why is there only a very thin film or net-work of ice? A. Because the earth absorbs the water, and leaves the icy film behind. Q. Does not water expand by heat as well as cold? A. Yes; it expands as soon as it is more than 42 degrees till it boils, and then it flies off in steam. Here A B measures the bulk of a portion of water at 42 degrees. Q. Why do water-pipes frequently burst in frosty weather? A. Because the water in them freezes; and as the water expands by frost, it bursts the pipes to make room for its increased volume. Q. When does water begin to expand from cold? A. Water (which is wisely ordained (Water freezes at 32°.) Q. Why does water expand when it freezes? A. Because it is converted into solid crystals, which do not fit close, like the particles of water. Q. Why is the water at the bottom of a river never frozen? A. Because when water is colder than 42 degrees, it instantly ascends to the surface; and (if it freezes) floats there till it is melted. (When a river is frozen, the water below the surface is never less than 42°.) Q. Show the wisdom of God in this wonderful exception to a general law. A. If ice were heavier than water, it would sink; and a river would soon become a solid block of ice, which could never be dissolved. Q. Why does not the cold ice on the surface of a river chill the water beneath, and make it freeze? A. 1st—Water is a very bad conductor, and is heated or chilled by convection only: 2ndly—If the ice on the surface were to communicate its coldness to the water beneath, the water beneath must communicate its heat to the ice, and the ice would instantly melt: and 3rdly—The ice on the surface acts as a shield to prevent the cold air from penetrating the river to freeze it below the mere crust. Q. Why does water freeze at the surface first? A. Because the surface is in contact with the air, and the air carries away its heat. Q. Why does the coat of ice grow thicker and thicker, if the frost continues? A. Because the heat of the water (immediately below the frozen surface) passes through the pores of the ice into the cold air. Q. Why then are not whole rivers frozen (layer by layer) till they become solid ice? A. Because water is so slow a con Q. Why does not running water freeze so fast as still water? A. 1st—Because the motion of the current dissolves the crystals as fast as they are formed; and 2ndly—The heat of the under surface is more freely distributed to the upper surface by the rolling water. Q. When running water is frozen, why is the ice generally very rough? A. Because little flakes of ice are first formed and carried down the stream, till they meet some obstacle to stop them; other flakes of ice (impinging against them) are arrested in like manner; and the edges of the different flakes overlapping each other, make the surface rough. Q. Why do some parts of a river freeze less than others? A. Because springs issue from the bottom, and (as they bubble upwards) thaw the ice, or make it thin. Q. When persons fall into a river in winter time, why does the water feel remarkably warm? A. Because the frosty air is at least 10 or 12 degrees colder than the water. (The water below the surface is at least 42°; but the air 32°, or even less.) Q. Why is shallow water frozen quicker than deep water? A. Because (as the whole volume of water must be cooled to 42 degrees before the surface can be frozen) it will take a longer time to cool down a deep bed of water than a shallow one. Q. Why is sea-water rarely frozen? A. 1st—Because the mass of water is so great that it requires a very long time to cool the whole volume down to 42 degrees: 2ndly—The ebb and flow of the sea interfere with the cooling influence of the air: and 3rdly—Salt never freezes till the surface is cooled down at least 25 degrees below the freezing point. Q. Why do some lakes rarely if ever freeze? A. 1st—Because they are very deep: 2ndly—Because their water is supplied by springs, which bubble from the bottom. Q. Why does the depth of the water retard its freezing? A. As the whole volume of water must be reduced to 42 degrees before the surface will freeze, the deeper the water, the longer it will be before the whole volume is thus reduced. Q. Why do springs at the bottom of a lake prevent its freezing? A. Because they keep continually sending forth fresh water, which prevents the lake from being reduced to the necessary degree of coldness. Q. Why is it colder in a thaw than in a frost? A. When frozen water is thawed, it absorbs heat from the air and objects around to melt its ice, in consequence of which the cold is greatly increased. Q. Why is it warmer in a frost than in a thaw? A. When water freezes it gives out its latent heat, in order that it may be converted into solid ice; and as much heat is liberated from the water into the air, we feel warmer. Q. Why does salt dissolve ice? A. Water freezes at 32°, but salt and water will not freeze till the air is 25° colder: if, therefore, salt be added to frozen water it becomes liquid, unless the thermometer stands below 7°, (which it never does in our island). Q. Will any thing do instead of salt? A. Yes; any acid, such as sulphuric, nitric, &c. Q. Why are salt and snow mixed together, colder than snow? A. When salt is mixed with snow, it dissolves the crystals into a fluid; and whenever a solid is converted to a liquid, heat is absorbed, and the cold made more intense. Q. Why does frost make the earth crack? A. During the warm weather the earth absorbed abundance of moisture, which the winter freezes: and (as water expands by frost) the expanding water thrusts the particles of earth apart from each other, and leaves a chink or crack behind. Q. Show the wisdom of God in this arrangement. A. These cracks in the earth let in the air, the dew and rain, and many gases favourable to vegetation. Q. Why does the earth crumble in spring? A. In spring the ice of the clods dissolves, and the particles of earth (which had been held apart by the expanded ice) are left unsupported, and tumble into minute parts (because their cement is dissolved). Q. Why does mortar crumble away in frost? A. If the mortar was not dried in the warm weather, its moisture freezes, expands, and thrusts the particles of the mortar away from each other; but (as soon as the frost goes) the water condenses and leaves the mortar full of cracks and chinks. Q. Why does stucco peel from a wall in frosty weather? A. If the stucco was not dried in the warm weather, its moisture freezes, expands, and thrusts its particles away from the wall; but as soon as the water condenses again by the thaw, the stucco Q. Why cannot bricklayers and plasterers work in frosty weather? A. Because the bricks and plaster would start from their position as soon as the frost came and expanded the mortar. Q. Why do bricklayers cover their work with straw in spring and autumn? A. Because straw is a non-conductor, and prevents the mortar of their new work from freezing during the cold nights of spring and autumn. Q. Why are water-pipes often covered with stall-litter in winter time? A. Because straw (being a non-conductor) prevents the water of the pipes from freezing, and the pipes from bursting. Q. Why are delicate trees covered with straw in WINTER? A. Because straw (being a non-conductor) prevents the sap of the tree from being frozen. Q. Can water be frozen in any way besides by frosty weather? A. Yes; in very many ways. For example—a bottle of water wrapped in cotton, and frequently wetted with ether, will soon freeze. Q. Why would water freeze if the bottle were kept constantly wetted with ether? A. Because evaporation would carry off the heat of the water, and reduce it to freezing point. Q. Why does ether freeze under the receiver of an air-pump, when the air is exhausted? A. Because evaporation is very greatly increased by the diminution of atmospheric pressure; and the ether freezes by evaporation. FREEZING MIXTURES. 1. If nitre be dissolved in water, the heat of the liquid will be reduced 16 degrees. 2. If 5 oz. of nitre, and 5 of sal-ammoniac (both finely powdered) be dissolved in 19 oz. of water, the heat of the liquid will be reduced 40 degrees. 3. If 3 lbs. of snow be added to 1 lb. of salt, the mixture will fall to 0° (or 32 degrees below freezing point). The two following are the coldest mixtures yet known:— 1. Mix 3 lbs. of muriate of lime with 1 lb. of snow. 2. Mix 5 lbs. of diluted sulphuric acid with 4 lbs. of snow. Q. Why is it more easy to swim in the sea than in a river? A. Because the specific gravity of salt water is greater than that of fresh, and therefore it buoys up the swimmer better. Q. How do cooks ascertain if their brine be salt enough for pickling? A. They put an egg into their brine. If the egg sinks the brine is not strong enough, if the egg floats it is. Q. Why will the egg sink if the brine be not strong enough for pickling? A. As an egg is heavier than water, it will sink if immersed therein; but if as much salt be added as the water can dissolve, the egg will float. Q. Why will the egg float in strong brine? A. Because the specific gravity of salt and water is greater than that of water only. Q. Why do persons sink in water when they are unskilful swimmers? A. 1st—Because (in their floundering about) they take in water at their nose and mouth, which makes them heavier: 2ndly—Fear contracts the body; and 3rdly—The water and fear take away the breath; and when the breath is taken from the body, its bulk is reduced, and it becomes heavier. Q. Why can quadrupeds swim more easily than man? A. 1st—Because the trunk of a quadruped is lighter than water, and this is the greatest part of them: 2ndly—The position of a beast in water is a natural one. Q. Why is it more difficult for a man to swim than for a beast? A. Because the head and limbs of a man (like those of a beast) are heavier than water, and these compose more than half his body: 2ndly—The position of a man in water is unnatural to him. Q. Why can fat men swim more easily than spare men? A. Fat is lighter than water; and the fatter a man is, the more buoyant will he be. Q. How are fishes able to ascend to the surface of water? A. Fishes have an air-bladder near their abdomen: when this bladder is filled with air, the fish increases in size; and (being lighter) ascends through the water to its surface. Q. How are fishes able to dive in a minute to the bottom of a stream? A. They expel the air from their air-bladder; in consequence of which, their size is diminished, and they sink instantly. |
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