(1)根据称重法:F浮=G-F=2N-1.2N=0.8N(2)根据基米德原理:F浮=ρ液gV排得:V排= F浮 ρ水g = 0.8N 1.0×103kg/m3×10N/kg =8×10-5m3,∵物体浸没在水中,∴V物=V排,m= G g = 2N 10N/kg =0.2kg,∴石块密度ρ= m V = 0.2kg 8×10?5m3 =2.5×103kg/m3.故答案为:0.8;2.5×103.