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Ch. 19 - Heat and the First Law of Thermodynamics
Giancoli Douglas - Physics for Scientists and Engineers 5th edition
Giancoli Douglas5th editionPhysics for Scientists and EngineersISBN: 9780137488179Not the one you use?Change textbook
All textbooksGiancoli Douglas 5th editionCh. 19 - Heat and the First Law of ThermodynamicsProblem 19.14
Chapter 19, Problem 19.14

(II) A 0.40-kg iron horseshoe just forged and very hot (Fig. 19–31), is dropped into 1.35 L of water in a 0.30-kg iron pot initially at 20.0°C. If the final equilibrium temperature is 25.0°C, estimate the initial temperature of the hot horseshoe..
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1
Identify the specific heat capacities involved: For iron, it is approximately 0.450 J/g°C, and for water, it is approximately 4.186 J/g°C.
Convert the mass of water from liters to grams knowing that 1 liter of water has a mass of approximately 1000 grams.
Set up the heat transfer equation assuming no heat loss to the surroundings. The heat lost by the iron horseshoe and pot should equal the heat gained by the water. Use the formula: \(m_{\text{iron}} imes c_{\text{iron}} imes (T_{\text{final}} - T_{\text{initial, iron}}) + m_{\text{pot}} imes c_{\text{iron}} imes (T_{\text{final}} - T_{\text{initial, pot}}) = m_{\text{water}} imes c_{\text{water}} imes (T_{\text{final}} - T_{\text{initial, water}})\).
Plug in the known values: mass of the horseshoe, mass of the pot, specific heat of iron, mass of the water, specific heat of water, initial temperature of the water and pot, and the final equilibrium temperature.
Solve the equation for the initial temperature of the hot horseshoe, \(T_{\text{initial, iron}}\). This will involve isolating \(T_{\text{initial, iron}}\) on one side of the equation and then calculating its value.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Heat Transfer

Heat transfer is the process by which thermal energy moves from one object to another due to a temperature difference. In this scenario, the hot iron horseshoe transfers heat to the cooler water and pot until thermal equilibrium is reached. Understanding the mechanisms of conduction, convection, and radiation is essential for analyzing how heat flows in this system.
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Specific Heat Capacity

Specific heat capacity is the amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius. Each material has a unique specific heat capacity, which influences how much heat it can absorb or release. In this problem, knowing the specific heat capacities of iron and water is crucial for calculating the initial temperature of the horseshoe based on the heat exchanged.
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Thermal Equilibrium

Thermal equilibrium occurs when two objects in contact reach the same temperature, resulting in no net heat flow between them. In this case, the hot horseshoe, water, and pot will eventually reach a common final temperature of 25.0°C. The principle of conservation of energy dictates that the heat lost by the horseshoe must equal the heat gained by the water and pot, allowing for the calculation of the horseshoe's initial temperature.
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