(2008? Harbin) a student made a simple electrolysis device shown in the figure, a small family experiment (Note: the device is airtight, and the reaction is good)

(1) after closing the switch, the circuit is on, the water began to be electrolyzed to release hydrogen and oxygen, A tube connected to the positive pole of the power supply to produce oxygen, B tube produces hydrogen.

② water is constantly being decomposed and release hydrogen and oxygen (2H20

? Energized? .

?

2H2↑+O2↑), the gas produced so that the pressure in tubes A and B increases, (or the air pressure in tube AB increases and is greater than the atmospheric pressure outside the tube, and analyze and discuss, as long as it is reasonable) the liquid in the tube is pressed into tube C of the connecting vessel.

(2) decomposition of hydrogen is insoluble in water, oxygen is not easily dissolved in water, hydrogen and oxygen density is smaller than water; in the role of gravity, the gas gathered in the upper part of the container.

(3) A tube is connected to the positive pole of the power supply, the gas is oxygen, oxygen test usually use a wooden bar with sparks, can make the wooden bar rekindle is oxygen.

The answer is: (1) ① electrode bubbles, after a period of time, tube A and tube B in the collection of gas volume ratio of about 1:2. ② liquid level rises; water decomposition of hydrogen and oxygen generated by the electrification of the AB tube pressure increases, the water pressed into the C tube, so the liquid level rises in the C tube;

(2) the density of hydrogen and oxygen is smaller than that of water, and hydrogen is insoluble in water, oxygen is insoluble in water;

(2) hydrogen and oxygen is smaller than water, and hydrogen is insoluble in water, oxygen is insoluble in water;

(3) the tube is connected to the positive pole of the power supply, and oxygen is not dissolved. is not easily soluble in water;

(3) the wooden bar with sparks.