Scientific Experiments with Toys
By Raymond B. Wailes
Many Novelty, Toy and “Jokers” Supply Stores sell small glass “meters” or “thermometers.” as they are called, attached to a card supposed to represent the quantity of intoxicating liquor the individual can consume, a state of health, denote a fortune, etc. The items are designed to provoke mirth and hilarity, but they operate on a scientific principle and can be used admirably for demonstrating some physical laws. What to do and how to conduct the experiments are details covered in the accompanying text.
THE glass “meter,” used in these experiments, consists of a glass bulb to which is welded a glass stem; the latter projects into but does not quite touch the interior bottom of the bulb.The whole device is partially filled with colored alcohol and evacuated. When the hand grasps the bulb, the liquid within the bull) expands and boils up into the stem of the tube, pulsating as if alive. Such devices are sold usually attached with a funny card purporting the instrument to be a “drunk meter” with which the degree of inebriety can be judged. They are also sold in the form of “Storkmeters,” “Fortune Telling” thermometers,” “Love Thermometers,” etc.
A very simple experiment showing that water absorbs infra-red or heat rays, can be shown by holding a small flat, water-filled pill – bottle between a candle flame and one of the meters. The dampening effect on the pulsating liquid contained in the meter is at once noted. The water acts as an absorber, or screen, for the infra – red rays. Alum solution works better than water (Fig. 1).
It is very simple to show that heat rays can be reflected similar to light rays. This can be done by forming a sheet of metal foil (such as is wrapped about tobacco, candy or photo film) into the shape of a concave reflector, and placing a candle flame at the focal point of the metallic screen, as shown in Fig. 2. When the screen throws the maximum amount of light upon the bulb of the meter, the meter will pulse very rapidly. The absorption of heat can be improved further by cautiously and momentarily thrusting the cool glass bulb into a smoking candle flame or the soot from a burning lump of camphor. The coating of soot absorbs the rays of heat more readily. This experiment also shows why dark clothes are “hotter” in the summer.
Alcohol and water become warm when they are mixed. The evolved heat is simply due to the heat of solution. If the tip of the stem of a novelty meter is snipped off, air enters and the vacuum is spoiled. In this form, novelty meter now is really an air thermometer, for if the air within the bulb is heated ever so slightly, the colored liquid in the bulb will rise in the stem; hence it can be used to detect heat.
For the experiment under discussion, place a metal nut over the stem of the air thermometer, made in the manner described, and place the device in a small glass or beaker filled with half an inch of water. The nut serves as a sinker. Now pour alcohol into the water, as illustrated in Fig. 3. It will mix, dissolve, and the heat produced will be shown by a rise of the colored liquid in the stem. Rubbing alcohol, denatured alcohol, grain alcohol, or automobile radiator alcohol, can be used with success in this experiment.
Using a meter with a weight attached to the bottom to float it upright in water, the principle of the hydrometer can be shown. On adding salt, sugar, or an acid, to the water, and stirring, the specific gravity, or density, of the water is raised by converting it into a solution, and the floating meter will rise or protrude farther from the liquid than before. By calibrating the stem, using thread and water-proof cement, a practical hydrometer can be made. Fig. 4 shows the hydrometer.
If the stem of a novelty meter be immersed upside down in a mixture of ice and salt, the volatile vapor of the liquid in the bulb above and outside the cold bath will condense into a colorless liquid in the stem. The heat of the air about the bulb causes more liquid to evaporate and soon the entire liquid which was previously in the bulb is now in the stem, quite colorless. The absence of color is due to the fact that the solid dyestuff does not vaporize. The experiment (Fig. 5) illustrates distillation at room temperature.
A humidity meter, or hygrometer, can be made by wrapping a cloth about the stem of a meter and immersing the tail or loose end of the cloth in a glass of water (Fig. 6). The water wets the cloth on the stem, and evaporates, thus cooling it, and the cooling effect is perceived by a pulsation of the liquid in the stem. It is the difference in temperature between the bulb and the stem which causes pulsation of the liquid within, so by timing the number of throbs per minute, you can arrange a scale of temperatures which will be fairly accurate, on dry days.
The last experiment can be made the basis of a funny little character which constantly appears to suck the colored liquid up into the stem throughout the day and night. The glass of water in the last experiment can be substituted by a narrow vial of water concealed inside a suitable figure which can be obtained at a toy store for a few cents. The cloth wrapped tube enters a hole made in the mouth of the figure. His hands can be bent to grasp the stem also. As long as there is water in the vial and the cloth wrapped about the stem of the meter is kept wet, the colored liquid pulses up and down in the tube. The motion continues for hours, and is dependent on the amount of moisture in the air. On a sultry, foggy, humid day, the movement of the liquid will be somewhat slow because the water of the cloth does not evaporate fast enough to produce a moderately cool temperature of the tube or stem.