Latent Heat

1. Latent Heat Materials can also go through a change in state called a phase change. Changes between solid, liquid, gaseous and plasma states. Energy Is required for these changes, but during this process the temperature of the material will not change. These changes typically occur at specific temperatures. The amount of heat required for a phase transition is given by: Q – Heat [J] L – Latent Heat [J/kg] M – mass [kg]

2. Latent Heat values for selected substances.

3. Example: 10 kg of ice at 0oC is dropped into a steam chamber at 100oC. How much steam is converted to water at 100oC? The negative sign on the mass is acceptable here since it represents the mass of steam that was lost (converted to water).

4. You have two containers of water. The first container has 200 g of water at 80oC and the second container has 200 g of water at 20oC. If the water in the two containers is mixed, what would the equilibrium temperature be for this mixture? T > 80 °C T  80 °C 50 °C ≤ T ≤ 80 °C T  50 °C 20 °C ≤ T ≤ 50 °C T  20 °C T < 20 °C

5. You have two containers of water. The first container has 200 g of water at 80oC and the second container has 100 g of water at 20oC. If the water in the two containers is mixed, what would the equilibrium temperature be for this mixture? T > 80 °C T  80 °C 50 °C ≤ T ≤ 80 °C T  50 °C 20 °C ≤ T ≤ 50 °C T  20 °C T < 20 °C T = 60oC

6. You have one container of water. The container has 200 g of water at 20oC. If a 200 g lead slug at 80oC is dropped into the water, what would the equilibrium temperature be for this mixture? T > 80 °C T  80 °C 50 °C ≤ T ≤ 80 °C T  50 °C 20 °C ≤ T ≤ 50 °C T  20 °C T < 20 °C T  22oC