Chapter U5, Problem C18.5RE

(a)

Interpretation Introduction

Interpretation: The heat that transferred to the pot needs to be calculated.

Concept Introduction: Thermodynamics is the analysis of heat transfer. Heat transfer direction is always from a hotter substance to colder one.

Answer to Problem C18.5RE

Total heat that transferred to the pot is 131250 cal.

Explanation of Solution

Given 5 kg iron pot is filled with 500 Ml of water.

The energy for water is as follows:

Mass of water

  $\begin{array}{c}\left(\text{m}\right)=500\text{mL}\\ \text{=}\text{500}\cancel{\text{mL}}\times \frac{\text{g}}{\cancel{\text{mL}}}\\ =500g\end{array}$

  $\left(\text{density}\text{=}\text{1g}/\text{mL}\right)$

Temperature change

  $\begin{array}{c}\left(\Delta \text{T}\right)=150°\text{C}-25°\text{C}\\ \text{=}\text{125}°\text{C}\end{array}$

Specific heat of water is $\text{1}\text{cal}/\text{g}\cdot °\text{C}$

The equation of heat is as follows:

  ${\text{H}}_{\text{1}}\text{=mCΔT}$

Here H is heat, m is mass, C is specific heat and T is temperature.

Put the values in above equation is as follows:

  $\begin{array}{c}{\text{H}}_{\text{1}}\text{=500}\cancel{\text{g}}\times \text{1}\frac{\text{cal}}{\text{g×}\cancel{\text{°C}}}\times 1\text{25}\cancel{°\text{C}}\\ \text{=62500cal}\end{array}$

The energy for iron is as follows:

Mass of water

  $\begin{array}{c}\left(\text{m}\right)=5\text{kg}\\ \text{=}\text{5000g}\end{array}$

Temperature change

  $\begin{array}{c}\left(\Delta \text{T}\right)=150°\text{C}-25°\text{C}\\ \text{=}\text{125}°\text{C}\end{array}$

Specific heat of iron is $\text{0}\text{.11}\text{cal}/\text{g}\cdot °\text{C}$

The equation of heat is as follows:

  ${\text{H}}_2\text{=mCΔT}$

Here H is heat, m is mass, C is specific heat and T is temperature.

Put the values in above equation is as follows:

  $\begin{array}{c}{\text{H}}_2\text{=5000}\cancel{\text{g}}\times 0.1\text{1}\frac{\text{cal}}{\text{g×}\cancel{\text{°C}}}\times 1\text{25}\cancel{°\text{C}}\\ \text{=68750cal}\end{array}$

Thus,

  $\begin{array}{c}{\text{total energy is=H}}_{\text{1}}{\text{+H}}_{\text{2}}\\ \text{=}\text{62500}\text{cal+68750}\text{cal}\\ \text{=131250}\text{cal}\end{array}$

Therefore total heat that transferred to the pot is 131250 cal.

(b)

Interpretation Introduction

Interpretation: The number of calories of energy transferred by rise the temperature of 200g of copper by $50°\text{C}$ needs to be calculated.

Concept Introduction: Thermodynamics is the analysis of heat transfer. Heat transfer direction is always from a hotter substance to colder one.

Answer to Problem C18.5RE

Iron pot will cool faster than water pot. This is because iron has less specific heat capacity than water.

Explanation of Solution

After heating same temperature for three minutes iron pot will cool faster than water pot. This is because iron has less specific heat capacity than water.