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26. Increase the electric conductivity and analysis of water

Material:Liquemin bottle, bottle with 2 ml mineral water ("Magnesia"), Liquemin bottle full of sodium sulfate solution (closed by a stopper which is pierced by 2 blunted hypodermic needles), Heparin bottle with crystals of sodium sulfate, spatula (piece of drinking straw), infusion bottle with tap water, plastic pipette, 9-Volt battery with battery clip, 2 light emitting diodes (LED), 2 electric wires with crocodile clips, goggles, matches.
Experiment:
1. Connect the battery with the clips. Close an electric circuit for a SHORT moment:
    Touch the contacts of the LED properly (differnt length!) with the bare ends of the clips.
2. Draw a sketch of the electric circuit (short and long contacts of the LED, battery, black (minus) and red wires (plus).
    [Mark clearly which of the the LED contacts you have to touch with the black (negative) wire].
3. Write 1, 2, 3, 4 on the blisters and transfer one pipette full of tap water (1), mineral water (2), crystals of sodium sulfate (3), tap water +  crystals of sodium sulfate (4).
4. Close the circuit through the substances in the blisters:
    Press the short contact of the LED to the black wire and dip the other one and the red wire first in blister 1, then in blister 2 and after cleaning in blister 3 and 4.
5. Write down your observations.
6. Turn the Liquemin bottle full of sodium sulfate solution upwards down.
    Put its 2 hypodermic needles into the Heparin bottle.
    Touch each of the needles by a bare end of the battery clip.
7. As soon as the liquid in the upper bottle is displaced by gas ask your teacher to test for oxyhydrogen gas.
Home work: Write a record on the lesson.  Some photos of the lesson.
You may collect the gases separately in two bottles and test for hydrogen and oxygen.