170 LABORATORY LESSONS IN GENERAL SCIENCE 



that there is formed at the same time one other substance, 

 zinc sulphate (ZnSO 4 ), which, so long as the water can hold 

 it in solution, dissolves as fast as it forms. When the 

 water becomes saturated (filled) with it, the ZnSO 4 will then 

 be deposited as a solid. 



2. Chemists have a shorthand way of stating chemical 

 changes known to have taken place, and in this case the state- 

 ment would be Zn + H 2 SO 4 -> H 2 + ZnSO 4 . The arrow 

 points toward the products of chemical change, and in these 

 products there must always be the same weight of material 

 (and same numbers of atoms of the substances) as found 

 in the substances entering into the change. 



3. Test the action of the dilute acid, (a) using the copper 

 (Cu) strip in place of the zinc ; (6) putting both strips down 

 into the liquid at the same time but not allowing the metals 

 to touch each other either within the liquid or outside. 



4. Fasten in place in the cap of the simple cell a strip 

 each of copper and of zinc. Connect the binding posts in 

 contact with these strips by a copper wire a couple of feet 

 in length. Now put the cap in place on the tumbler with 

 the metal strips in the liquid close together but not touching 

 each other. Observe the strips in the liquid long enough to 

 state what change from the former conditions is now noted. 



5. Bring the wire connecting the binding posts down 

 lengthwise over a compass needle which is at rest in a north 

 and south direction, and note the effect. Repeat several 

 times to be sure whether any disturbance of the needle re- 

 sults from the presence near it of a current-bearing ("live") 

 wire. Note the effect on the compass needle of bringing 

 near it and of taking away a permanent magnet. Try a 



