Help! Please!? ?

Question

Here is a question from my homework that I don't really get how to do:

Suppose a sample of aluminum is placed in a 25mL graduated cylinder containing 10.5 mL of water. the level of the water rises to 13.5 mL. What is the mass of the aluminum sample?

Answer 1

Step 1: 13.5 ml minus 10.5 ml = 3 ml.  Therefore, the aluminum sample is has a volume of 3 ml

Step 2: Find the specific gravity of aluminum from a table.  The site shown below shows that the specific gravity of AL is 2.6989.  I'll round this to 2.7.

Step 3: Water has a mass of 1 gram per ml at standard temperature.  The specific gravity of AL is 2.7, so the mass of the AL in the cylinder is 3 times 2.7 grams, or 8.1 grams.

Answer 2

If the water is displaced 3mL, then 3mL (or cubic centimeters) of aluminum have been placed in the graduated cylinder. Aluminum is about 2.7 g/mL, so 2.7 x 3 = 8.1

The aluminum is 8.1grams

If something sinks in a fluid, it will displace equal volume. However, if it were something which floats, remember that it would displace an equal MASS.

Hope this helps.