Transcript Document

Phase Change Calculations
pg 5
PHYSICAL CONSTANTS FOR WATER
FREEZING POINT = 0.0°C
BOILING POINT = 100°C
SPECIFIC HEATS: SOLID H2O
LIQUID H2O
GASEOUS H2O
HEAT OF FUSION = 335 J/g
HEAT OF VAPORIZATION = 2260 J/g°C
= 2.1 J/g°C
= 4.18 J/g°C
= 2.0 J/g°C
Temperature (oC)
Phase-Change Diagram
Heat = mass x ΔT x Cg Gas
Heat = mass x HVaporization
B pt
Liquid
M pt s ↔ l
Solid
l↔g
Heat = mass x ΔT x Cl
Heat = mass x HFusion
Heat = mass x ΔT x Cs
Heat (J)
How much energy is needed to change the temperature
of 123 grams of liquid water from 20°C to 35°C?
Heat = mass x ΔT x Cl
Heat = 123 g x 15 °C x 4.18 J/g°C = 7712 J
How much energy is needed to change 26.5 g of solid
water from 0.0°C to liquid water at 48.3°C?
s↔l
Heat = mass x HFusion
Heat = 26.5 g x 335 J/g
= 8878 J
ΔT
Heat = mass x ΔT x Cl
Heat = 26.5 g x 48.3°C x 4.18 J/g°C = 5350 J
Total Energy = 14228 J
5.00 grams of solid water at 0.0°C are heated to 78.3°C.
How much energy must be added to cause this change?
s ↔ l Heat = mass x HFusion
Heat = 5.00 g x 335 J/g
ΔT
= 1675 J
Heat = mass x ΔT x Cl
Heat = 5.00 g x 78.3°C x 4.18 J/g°C = 1636 J
Total Energy = 3311 J
How many joules of energy must be added to 75.0
grams of solid water at -17°C to melt and raise its
temperature to 99°C?
ΔT Heat = 75.0 g x 17°C x 2.1 J/g°C
= 2678 J
s ↔ l Heat = mass x HFusion
Heat = 75.0 g x 335 J/g
ΔT
= 25125 J
Heat = mass x ΔT x Cl
Heat = 75.0 g x 99°C x 4.18 J/g°C = 31037 J
Total Energy = 58840 J
How much energy is released when 9.45 g of gaseous
water at 100.0°C is condensed and cooled to 18.6°C?
g ↔ l Heat = mass x HVaporization
Heat = 9.45 g x 2260 J/g
ΔT
= 21357 J
Heat = mass x ΔT x Cl
Heat = 9.45 g x 81.4°C x 4.18 J/g°C = 3215 J
Total Energy = 24572 J
To what temperature will liquid water be raised when
1298 joules of energy are added to 4.50 g of liquid water
at 0.0°C?
ΔT
Heat = mass x ΔT x Cl
1298 J = 4.50 g x ?°C x 4.18 J/g°C
1298 J
= ?°C = 69°C = ΔT
4.50 g x 4.18 J/g°C
0.0°C + 69°C = 69°C