ten little fingers - arvind gupta (4 mb pdf)

FUN WITH HEATHot or Cold?Dancing CoinTake three glasses, one with very hotwater, another with very cold water andthe third with water at room temperature.Then put one finger in the hot and theother finger in the cold water. Keep themfor a minute. Then put both the fingers inthe middle glass You will find that thewater is warm to the finger that was inthe cold water, but is cold to the fingerwhich was in the hot water.Take an empty glass bottle. Apply a few drops ofwater on the mouth of the bottle and cover it with aone-rupee coin. Then put your hands around the bottleand hold it for half a minute. The coin will begin tojump up and down. This shows that air expands whenheated. When you hold the bottle with your hands, thecold air in the bottle becomes warmer Warm airexpands and comes out of the bottle and makes thecoin dance.Fill all 3 cans with the same volume ofhot water. Cover them with lids andstand them in a cool place. Record thetemperature of water in each canevery 5 minutes. Black surfaces bothabsorb and radiate heat more quicklythan shiny or white surfaces.Paper PanPlace a coin betweenthe nails, then heat thenails The coin cannot beremoved now as thenails have expanded.Non-burning PaperCut a metal strip so that itfits exactly between twonails. Heat the strip andthen try to fit it betweenthe nails.Fireproof HandkerchiefThe pan will not burn, as thetemperature of the paper never risesabove 100 degrees Centigrade.Ring the nailThe coin on the pieceof paper conducts heataway before the paperburns.Take a cotton handkerchief andtightly rap a coin in it. Put the coinon a flame. The coin conducts heataway before the cloth can burn.Measuring conduction ratesMake a wire loop which is just big enoughto pass over the head of the nail. Now heatthe nail. Ask the children why the loop willnot fit over the hot nail head.Take two wires of different materials - a copperwire and a steel wire. Stick small stones along thewires using candle wax. Hold the wires in the flameand record the time each of the stones drops offeach wire. This will tell you which of the twomaterials is a better conductor of heat.