(2) Aluminum is an active metal, and it is easy to form an oxide film on its surface in air, which affects the experimental progress and needs to be polished with sandpaper.
The aluminum wire was immersed in copper sulfate solution to replace copper, and the red substance was deposited on the surface of the aluminum wire. The equation is 2al+3cuso4 = Al2 (SO4) 3+3cu.
Aluminum is more active than copper because there are bubbles in the reaction between aluminum and hydrochloric acid, but copper wire is not.
(3) It is speculated that AlCl3 or AlCl3 and CuCl2 may exist in the liquid after the reaction in experiment 1; In the first experiment, the liquid after the reaction can be AlCl3 or AlCl3 and HCl. The mixture of the two solutions may be: ①AlCl3, HCl, Cucl22AlCl3, HCl③AlCl3, Cucl24AlCl3.
During the experiment, ① the solution is colorless, so it does not contain copper chloride, so it is wrong to guess ① ③.
② Add a small amount of this solution into the test tube, and then add enough sodium hydroxide solution. If there is no phenomenon at first, it will precipitate into white after a while, indicating that conjecture 2 is established.
So the answer is: (1) conducting electricity; (2) removing the oxide film on the surface; Red; 2Al+3c uso 4 = Al2(SO4)3+3Cu； There are bubbles on the surface of aluminum wire, but not copper wire; (3) aluminum trichloride; (1) (3) There was no phenomenon at first, and then there was white precipitation.