It takes 2.1×106 J of heat to bring a quantity of water from 21C to a boil. What would be the mass of the water in kg?
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q = mc (change in temp)
boiling pt of water is 100C. so change in temp = 100-21 = 79 C. also usually you should change this to Kelvin, but because you are looking for the change in temp and not the temp itself, you don't have to change it, because no matter what it will be the same (i.e. 100+273 = 373 K and 79+273 = 352K, but 373-352 = 79!)
c for water is 4.18 [J/(g·K)(its one thing you should always remember)
2.1x 10^6 = m (4.18) (79)
m = 6359.3 g
convert that to kg = 6.3593 kg
boiling pt of water is 100C. so change in temp = 100-21 = 79 C. also usually you should change this to Kelvin, but because you are looking for the change in temp and not the temp itself, you don't have to change it, because no matter what it will be the same (i.e. 100+273 = 373 K and 79+273 = 352K, but 373-352 = 79!)
c for water is 4.18 [J/(g·K)(its one thing you should always remember)
2.1x 10^6 = m (4.18) (79)
m = 6359.3 g
convert that to kg = 6.3593 kg