An empty iron pan (mass of 3.0 kg) is placed on a stovetop burner and the burner

Question

An empty iron pan (mass of 3.0 kg) is placed on a stovetop burner and the burner is turned on. The burner and pan are both initially at 22 degree C. The specific heat of iron is 450 J/(kg C degree) and the specific heat of copper is 390 J/(kg C degree) a. If the burner heats the pan to 175 degree C, what is the amount of heat added to the pan? b. If the burner supplies 500 W of power and assuming nothing else heats up except for the pan, how long does the pan take to reach 175 degree C? c. If the pan were made of copper (with the same mass) would it take a longer time, a shorter time, or the same amount of time to heat to 175 degree C on the same burner? Explain

Explanation / Answer

Weight of Pan (Iron) = 3 kg

Initial temperature of Pan = 22 °C

Specific heat of Iron = 450 J/(kg.°C)

Specific heat of Copper = 390 J/(kg.°C)

(a) Iron pan is heated up to 175 °C

To calculate heat required (Q)

Heat required for heating (Q) = (Weight of body)*(specific heat)*(temperature difference)

Q = (3.0 kg)*[450 J/(kg.°C)]*( 175 °C - 22 °C)

    = 3.0*450*153

   = 206550 J

Heat added to the pan is 206.55 kJ

(b) Burner supply heat with power of 500 W

It means, it supply heat 500 J/s

Time taken in supplying heat, Q = 206550 J is given by –

Time = (Heat required)/(power)

         = (206550 J)/[500 J/s]

         = 413.1 seconds

(c) For the case of Copper Pan è Specific heat of Copper = 390 J/(kg.°C)

Heat required for heating copper pan

Q = (3.0 kg)*[390 J/(kg.°C)]*( 175 °C - 22 °C)

   = 179010 J

Time taken in heating up = (179010 J) / (500 J/s)

                                        = 358.02 seconds

Copper pan takes shorter time than iron pan to heat up to same temperature as it has lower specific heat as compared to iron pan.

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