Multiple Choice
How much heat must be removed from 0.7 kg of water at 23°C to cool it to 0°C and completely freeze it?
20. Heat and Temperature
Latent Heat & Phase Changes
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How much heat is needed to change of liquid water at into steam at ?
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Verified step by step guidance1
First, understand that the problem involves two main processes: heating the water from 20°C to 100°C, and then converting the water at 100°C to steam. Each process requires a different calculation.
Calculate the heat required to raise the temperature of the water from 20°C to 100°C using the formula: \( Q_1 = m \cdot c \cdot \Delta T \), where \( m \) is the mass of the water, \( c \) is the specific heat capacity of water (4.18 J/g°C), and \( \Delta T \) is the change in temperature.
Convert the volume of water (1.0 L) to mass. Since the density of water is approximately 1 g/mL, 1.0 L of water is equivalent to 1000 g.
Calculate the heat required for the phase change from water to steam using the formula: \( Q_2 = m \cdot L_v \), where \( L_v \) is the latent heat of vaporization for water (2260 J/g).
Add the heat calculated for both processes to find the total heat required: \( Q_{total} = Q_1 + Q_2 \). This will give you the total energy needed to convert 1.0 L of water at 20°C to steam at 100°C.
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