A density bottle weighs 0.25 and when empty and 0.75 when filled with water and 0.65 and when filled with alcohol. Calculate

Question

1. The volume of the bottle
2. The density of the alcohol

Answer 1

I presume you are using the density of water as 1.00 g/cc. Also I assume those numbers are in grams.
0.75 g = mass empty bottle + H2O
-0.25 g = mass empty bottle
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0.50 g = mass water in the density bottle
volume of density bottle = mass/density = 0.50 g/1.00 g/cc = 0.50 cc

0.65 g = mass empty bottle + alcohol
-0.25 g = mass empty bottle
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0.40 g = mass alcohol
density alcohol = mass alcohol/volume alcohol = 0.40/0.50 = 0.80 g/cc

Answer 2

I don't know what "weighs 0.25" means. I'll assume 0.25kg = 250g, and you can revise the solution as needed to fit your interpretation.

if water has density 1g/cm^3 then the bottle holds 500cm^3
so the alcohol has density (650-250)/500 = 0.8 g/cm^3