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WATER at 1 Atmosphere

The table presents selected thermodynamic properties of water at a pressure of One Atmosphere over the range of temperatures, -40°C to 500°C. This is the "solid-to-liquid" ~ melting phase change temperature and the "liquid-to-solid" ~ freezing temperature one atmpsphere. At 0°C, water is either solid (with solid properties) or liquid (with liquid properties). To tabulate both sets of properties at the same 0°, in the same column, temperature is awkward. Consequently we notate the solid to have the temperature 0-°C and the liquid to have the temperarure, 0+°C. Thus the temperatures, 0-°C, means "at 0°C" but solid and the temperature 0+°C means "at 0°C" but liquid. The same conventiion is used for 100°

The data of this table present states of water always at the pressure, 1 atmosphere over the temperature range, -40°C to 500°C).

Water at One Atmosphere
p
(Ts(p))
 -40°C  0-°C
(solid~s)
 0+°C
(liquid~f)
 100-°C
(liquid-f)
 100+°C
(gas-g)
 500°C
101.3 kPa
(100°C)
v ~ cm³/g
u ~ J/g 
h ~ J/g
1.08
-410
-411
vs = 1.09
us = -332
hs = -333
vf = 1.00
uf = 0.10
hf = 0.10
vf = 1.04
uf = 418
hf = 419
vg = 1680
ug = 2505
hg = 2675
3534
3130
3488

- - - - - - -

Problems below ask you to use the tabular data (water "at one atmosphere) to answer some questions regarding "state" and "events" of water occuring - at (the ambient pressure) 1 atmosphere.

1) 5000 grams of water exists at 1.0 atmosphere and 500°C. What is the volume of the water?

Solution:   V = mv(1atm, 500°C) = 5000g (3534 cm3/g) = 17.7m3

2) Three grams of liquid water and 5000 cubic centimeters of gaseous water coexist in equilibrium at one atmosphere. What is the temperature? Calculate the enthalpy, H?
♦  Phases of water that coexist at one atmosphere have the temperature, 100°C. The enthalpy is:

H = mf hf + mg hg

H = mf hf + (Vg/vg) hg

H = 3g(419 J/g) + [5000 cm3/1680 cm 3/g](2675 J/g)

H = 9218 J


3) Determine the volume of 400grams of steam at 1.0 atmosphere and a) 300°C. b) 167°C.
  300°C is a nice number because it is midway between the table entries, 100+°C and 500°C. The fast answer is V = m{[v(500°C) + v(100+°C]/2}. Below we show all steps of the interpolation.

interpolate_1.gif

interpolate_167.gif

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