The diagram given below represents an experiment to prove the importance of a factor in photosynthesis (a leaf partly covered with black paper held by clips). Answer the questions that follow: The diagram given below represents an experiment to prove the importance of a factor in photosynthesis (a leaf partly covered with black paper held by clips). Answer the questions that follow:
Draw a neat, labelled diagram of an experimental setup to show that oxygen is released during photosynthesis.
Topic: Hydrilla experiment — diagram
Answer
Draw the standard HYDRILLA experiment: • a BEAKER containing pond water • sprigs of HYDRILLA with their cut ends upward • a SHORT-STEMMED FUNNEL inverted over the plants, raised slightly on a support to keep it off the bottom • a TEST TUBE full of water inverted over the funnel stem • BUBBLES of gas rising from the cut ends, and GAS COLLECTED at the top of the test tube • the apparatus placed in SUNLIGHT
Labels required: beaker, pond water, Hydrilla, funnel, support, test tube, gas collected (oxygen), sunlight.
THE TEST that proves the gas is oxygen, and it should be written beside your diagram: introduce a GLOWING SPLINT into the collected gas — it RELIGHTS, since oxygen supports combustion.
WHY EACH PART IS THERE, because examiners ask: HYDRILLA — an aquatic plant, so its gas can be collected as bubbles under water the SUPPORT under the funnel — keeps it off the bottom so water can circulate beneath INVERTED FUNNEL AND TEST TUBE — channel and trap the gas SUNLIGHT — the essential condition; in darkness no bubbles appear, which serves as the control
Sodium bicarbonate may be added to the water to supply extra carbon dioxide and speed the reaction.