Calciumhydroxide solutionprovides the chemical test forcarbondioxide,
which makes it turnmilky white. No othergas, whenbubbled into it, will
make it dothatand make itafterwardform this whiteprecipitate.Theequation
for this reactionis as follows (the arrowpointingdownwardshows that a
precipitatewas formed):
CO 2 +Ca(OH)2~CaCOa ~ +H 20
Thematchyou lit wentoutimmediately when you blew on it. Firescannot
burn withoutoxygen. Sincecarbondioxide is a heavy gas, it lies close to the
burningobject and keeps out theoxygen-containingair. This is whyyourbreath,
whichcontainscarbondioxide, extinguished the match.
HOW TO MAKE AFIRE EXTINGUISHER
Gather these materials:A l-holedrubberstopper;a milkbottle;a glass tube
aboutone inch shorterthanthe milk bottle,stretchedat one end to form a
nozzle; a small,narrowperfumebottle;a 6-inchstring; sodiumbicarbonate
(NaHCOa)andacetic acid(CHaCOOH).
Follow this procedure: Fill the milkbottlehalfway with water. Add 3 tea-
spoonfulsofsodium bicarbonateto it. Tie a string aroundthe neckofthe
perfumebottle.Fill the perfumebottlewith acetic acid. Suspend theperfume
bottlein the milkbottle,letting the string hang over the rimofthe milkbottle
andholdthe string so thebottledoesn'tdrop.Putthe glasstubinginto the
rubberstopperandthestopperinto the milk bottle. Thestopperwill hold the
string in place.