posted by Victoria on .
The level of water in a graduated cylinder is at the 100 mL mark. When a platinum crucible floats on the surface of the water, the level reads 157.9 mL. When the crucible is totally immersed in the same cylinder, the level reads 102.70 mL. What is the density of platinum? The density of water is 0.997 g/mL at 25C.
The question just asks us to describe the strategy we would use to solve the problem above.
The priciple of floation says that the mass of water displaced (in this case increased) equals to the mass of the floating object.
So the crucible weighs (157.9-100)*0.997 grams.
When the crucible is submerged (without trapping air bubbles), the increase in volume equals the volume of the crucible.
The volume of the crucible is (102.7-100) c.c.
The density at 25 degrees is therefore the weight divided by the volume.