I need to find the density of Gasoline and Kerosene

Question

I have 13.5g of gasoline and 16g of kerosene and I have to find the densities of both! yikes!! I can't seem to match the books answers. Can anyone show me how to calculate the correct answer?

Answer 1

Sounds like you're doing an experiment.   You have more than 10 mL of each.  But you could also use 5 mL.    You have to accurately measure a volume (10 mL) of the fluid.  This means a graduated cylinder, a volumetric flask, or even a good quality glass syringe.  Be careful, measure the volume precisely.   Before measuring it, weigh the vessel when empty.  Then weigh it again after you fill it with exactly 10.00 mL (5.00 mL.. whatever).    Divide the measured mass (weight full - weight empty) by the measured volume to get density.   There is a range of densities, and density is also a function of temperature, so even if you do it perfectly, your answer may not match someone else's.  

An alternate method if you don't have something that measures precisely, is to fill a small vessel accurately to be 'full' or to a line that you create.   Do the above experiment with it, and then do it again to measure the density of water.  The density of water is 1.00 (at standard temperature) so its mass in grams tells you the volume in mL.  You divide the mass of the other things by the mass of the water to get the density.

Answer 2

If you need the densities, then look them up.

A quote from Wikipedia (first entry on Goggle search)

"The density of gasoline is 0.71–0.77 g/cm3"

The range is due to different grades and additives, like ethanol.

The density of kerosene is 0.817 g/cm3

http://www.simetric.co.uk/si_liquids.htm

============= Follow up ================

You wrote:  "I looked up the densities. I just don't know how to get the volume. I know the mass and the density. but the volume must be wrong because I can't seem to get the density listed in the book or on the internet."

Ahhh.  You didn't say that.  Volume can be determined with a graduated cylinder.  So you've measured a volume and a mass and then you computed the density (D=m/V) and your computed value doesn't match the accepted value.  Is that right?  Obviously, there is room for error, but not much.  The graduated cylinder will give the volume in mL which is the same as 1 cm^3.  

I would probably trust my measurements more than the published numbers.  As I pointed out, there can be variations based on the current formulation of the gasoline and kerosene.  Different additives, different formulas, and the use of ethanol could make a difference.