i need your help fast
by balam23 on 10/17/05 at 02:45:48
Hola I need your help. I need calculate the energy in joules, therms, and kilowatt-hours that is required to heat 1 cup of water from 25 Celsius to 100 Celsius. Besides calculate the cost of heating 1cup of water using an electric stove when the electricity=$0 .1143/kW.hr and calculate the cost of heating 1 cup of water using a gas stove when the natural gas=$1.07/therm AND calculate the mass of natural gas that burns to boil 1 cup (240ml)of water from 25 celsius to 100 celsius ???
Re: i need your help fast
by Robert Fogt on 10/17/05 at 03:10:25
The formula would be: mass * temperature change * specific heat
mass is in grams, temperature change is in degree Celsius, and specfic heat is in calories/gram degree Celsius.
We know that the specific heat of water is 1 cal/gºC, so we just need to calculate the rest.
Water at 4º C has a density of 1 gram/cubic centimeter, while at 20º C it has a density of 0.998 gram/cubic centimeter. I will use the 20º C value, but keep in mind your answer may differ from your teachers as most textbooks use the 4º C value as an estimate.
1 cup of water at 20º C = 236.113826 grams
temperature change = 100º C - 25º C = 75º C
Now enter into the formula:
236.113826 grams * 75º C * 1 calorie/gram º C = 17708.53695 calories
You can now use the energy conversion page to convert that into which unit you need.