4）v瓶=（m总-m空）/p水
=（700g-200g）/1
=500cm³
m某=m水+25g
=500g+25g
=525g
p某=m某/v瓶
=525g/500cm³
=1.05g/cm³
答：此液体密度为1.05g/cm³.
5）m酒=（v瓶*3/4）*0.8
=（500cm³*3/4）*0.8
=300g
m水=（v瓶-v水）*p水
=（500cm³-375cm³）*1g/cm³
=125g
p混=（m酒+m水）/v瓶
=(300g+125g)/500cm³
=0.85g/cm³
m酒瓶总=m酒+m水+m瓶
=300g+125g+200g
=625g
答：酒精溶液的密度为0.85g/cm³；瓶和酒精溶液的总质量为625g.