Hello, Emily,
We can make some progtress on the final answer, but the problem doesn't tell us the volume of fuel that we need in order to calculate the total mass.
The portion we can address is that the problem wants an answer in kg, but the density is provided only in grams. We can make a conversion factor based on the fact that:
1000 grams = 1 kilogram
Divide by grams to get: 1 = (1 kg/1000 g)
This conversion actor is equal to 1, so we can multiply it by anything and the real value won't change, but the number will change to accomodate the new units.
Multiply this by the given density: (0.0779 g/cm3)*(1 kg/1000 g) = 7.79x10-5kg/cm3
This value is very low, so I'm guessing something like H2. What we need however, is a volume of the fuel to calculate it's mass. For example, a volume of 10 cm3 can be multiplied times the density. The cm3 units cancel, leaving a value of 7.79x10-4kg.
Bob
