Sun28November0628PM 28
1000 mL of water at 0°C is contained in a water-bath at a pressure of 1 bar. It is heated by a 1 kW element.
The specific heat capacity of water is 4181 J/(kg°C) or J/(kg K).
Approximately how long will it take to raise the temperature of the water by 10°C?
(Please select 1 option)
42 seconds This is the correct answer
70 minutes
0.42 seconds
7 minutes Incorrect answer selected
4.2 seconds
Explanation
When energy in the form of heat is transferred to an object the change of temperature will depend on a number of factors. These are:
Mass of the object
Chemical composition of the object, and
The amount of heat energy transferred to the object.
The specific heat capacity of a substance is the amount of energy needed to change the temperature of 1 kg of the substance by 1°C.
The energy required to raise the temperature of an object is given by this equation:
E = m × c ×
Where:
E = energy required to heat an object
m = mass of object
c = specific heat capacity of the substance
The specific heat capacity of water is 4181 J/(kg°C)
Therefore the energy required to raise 1kg of water by 10°C is:
1 kg × 4181 J/(kg°C) × 10°C = 41810 J
The watt (W) the derived SI unit of power in J/s. A 1 kW or 1000 W heater would be expected to supply 1000 J/s.
The approximate time it would take the 1 kW heater to raise the temperature of 1000 mL of water by 10°C is:
41810/1000 = 41.8 seconds.
Answer Statistics
1
52%
2
5%
3
3%
4
27%
5
15%
Times answered: 243