Initial volume of the gas (V1) = 10 inches^3
Initial pressure (P1) = 5 psi
Final pressure after compression of the gas (P1) = 10 psi
Let us assume the final volume of the gas (V2) = x
According to Boyle's Gas law, the pressure and volume of a gas remains constant under ideal condition. Then
P1V1= P2V2
5 * 10 = 10 * x
50 = 10x
x = 50/10
= 5 cubic inches
So the volume of the gas after it was compressed was 5 cubic inches. I hope the procedure is clear enough for you to understand.
Fuel is produced by fermenting Ethanol
Maybe this will help you out:
Momentum is calculate by the formula:

Where:
P = momentum
m = mass
v = velocity
The SI unit:

So the unit of momentum would be:

Impulse is defined as the change in momentum or how much force changes momentum. It can be calculate with the formula:
I = FΔt
where:
I = impulse
F = Force
Δt = change in time
The SI unit:
F = Newtons (N) or 
t = Seconds (s)
So the unit of impulse would be derived this way:
I = FΔt
I =
x 
or

You can then cancel out one s each from the numerator and denominator and you'll be left with:

So then:
Momentum: Impulse
