Name_____________________________________ Period________
energy ws4
Energy with Phase change WS II Useful information (see previous worksheet and powerpoint presentation for a full explanation of terms):
q = mcT
cwater(l) = the specific heat of liquid water = 4.184 J/goC cwater(s) = the specific heat of ice = 2.03 J/goC cwater(g) = the specific heat of steam = 2.01 J/goC
Hvap the energy required to convert liquid water to steam = 2259 J/g Hfus = the energy required to convert ice to liquid water = 334 J/g
Example: How many joules of energy are required to heat 25 grams of water from -28 to +130oC? Solution: Heating up that 25 grams of ice involves 5 separate steps: 1. The ice heats from -28 OC to 0OC: q = mcT = (25 g)(2.03 J/gOC)(28OC) = 1,421 J 2. At 0OC the ice melts: 334 j/g x 25 g = 8350 J 3. The water then heats from 0 to 100 OC: q = mcT = (25 g)(4.18 J/gOC)(100OC) = 10,450 J 4. The water boils at 100 OC: 2259 J/g x 25 g = 56,475 J 5. The steam heats from 100 to 185 (in reality this could only happen as pressure increases); q= mcT = (25)(2.01)(85) = 4271 J Total: 80,967 J
1)
How many joules are required to heat 75 grams of water from -85 0C to 1850C?
2)
How many joules are required to heat a frozen can of ice (360 grams) from -5 0 C (the
temperature of an overcooled refrigerator) to 110 0C (the highest practical temperature within a microwave oven)?
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