toothpick sothatit flames. Blowoutthe flame, and immediately, while the
toothpickstill glows, put it in the test tube. Then do the same thing with the
test tube kept over the plantthatwas kept in thedark.
You will observe:The test tube over theplantkept in thesunlightappears
to be empty, but when you placed the glowingtoothpickin it, the stickburst
into flame. This happened because the test tube contained oxygen. The
toothpicktest on the test tube over the plantkept in a closet shows quite a
difference! Since this test tube stillcontainswater, the glowingtoothpickwill
sputterout.Itis because ofsunlightthatgreen plants are able tomanufacturefood.
As you know, this process is calledphotosynthesis. But plantsnotonlyproduce
food-asa by-productthey give off the gas oxygen. Oxygen is releasedthrough
thestomates,usually on theundersurfaceofeach leaf.
Oxygen is needed to make things burn. Therefore, since thetoothpick
placed in the test tube over theplantkept insunlightburstinto flame, you
knowthatoxygen was present.
The oxygen given off by green plants is a necessarypartofthe airbreathed
in by all living things. See how great is theimportanceof greenplants! They
not onlymanufacturefood for us as well as forotheranimals, they alsoreturn
oxygen to the air we need inorderto live.
SHOWING THAT GREEN PLANTS GIVE OFF WATER FROM THEIR
LEAVES
Materials: A large, healthy leaf from a geraniumplant,two glasses or
wide-mouthedjarsthe sizeofglasses, a shirtcardboard,water, a smallamount
ofvaseline.