specific heat has units of J/g*K or joules/gram/degree kelvin. Typically, specific heat is the heat required to raise the temperature of 1 gram of some material by 1 degree K. Heat capacity has units of J/K; i.e., note no "specificity" in amount as in grams. There is a good discussion here.
http://en.wikipedia.org/wiki/Heat_capacity
For the problem, 1 watt is 1J/s. You have 1000 watts so it is 1000 J/s. You run it for 2 minutes which = 1000 x 2 x (60 s/min) = ?. It is only 80% efficient; therefore, ? x 0.8 = q = heat produced.
Then q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
Use 4.184 J/g*C for specific heat H2O unless you are given some other number.
What is the difference between specific heat and heat capacity? If you heat 500g of H2O initially at 8C in a 1000 W microwave with 80% efficiency for 2 minutes, what will the final temperature be?
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