Self Test 7.1A expansion of water as it freezes

[Kayla Denton 1A]

I got a different answer than the textbook for self test 7.1 A. The question was, "Water expands when it freezes. How much work does 100. g of water do when it freezes at 0°C and pushes back the metal wall of a pipe that exerts an opposing pressure of 1070 atm? The densities of water and ice at 0°C are 1.00 g/cm^3 and 0.92 g/cm^3, respectively."

I used the formula w = -P(ex) times delta V.
Delta V = V(final) - V(initial).
V final is ice: 100. g x cm^3/0.92g x m^3/10^6 cm^3 = 1.09 x 10^-4 m^3.
V initial is water: 100. g x cm^3/1.00g x m^3/10^6 cm^3 = 1.00 x 10^-4 m^3.
(1.09 x 10^-4) - (1.00 x 10^-4) = 9.00 x 10^-6 m^3 for change in volume.
Then pressure = 1070 atm x 101325 Pa/atm = 1.084 x 10^8 Pa.
So w = -(1.084 x 10^8)(9.00 x 10^-6) = -976 rounded to -0.98 kJ.

The answer in the book is -0.9 kJ.
Did I make a mistake somewhere?
Thanks!! :)

[Chem_Mod]

Hi Kayla,

You got all of the steps correct, it's just that the answer discrepancy comes from excessively rounding throughout the problem. Don't round off for sig figs until the very end of your calculation, otherwise you lose valuable information and get an incorrect answer.

Take a look at pages 112-113 in the course reader for a thorough guide to sig figs.