Questions+of+latent+heat

The amount of thermal energy required to change its state from liquid to gas (latent heat of vaporisation), or liquid to solid (latent heat of fusion) for a 1 kg of substance.
 * Latent heat practice questions **
 * 1. **Define latent heat.
 * 2. **Determine the unit of latent heat.

Answer 3) 1.6 x 105 J Answer 4) 1.2 x 105 J  Answer 5) 8.3 x 105 J  Answer 6) 58mins Answer 7) 31 0C
 * 3. **Find the energy required to melt 2.5 kg of gold at its melting point.
 * 4. **Copper has a melting point of 1083°C. Find the energy required to melt 200 g of copper originally at room temperature of 22°C.
 * 5. **A 2.0 L bottle of water at 20°C is placed in the freezer of a refrigerator. How much heat must be removed by the refrigerator to freeze this water?
 * 6. **A child wanting to make a cordial ice block places 200 g of cordial at 25°C in the freezer. If the freezer can remove energy at the rate of 25 joules per second, what time will it take for the cordial to freeze? (Assume the specific latent heat and specific heat capacity of cordial are the same as water.)
 * 7. **Two ice blocks of mass 20 g each are placed in 500 g of water at 40°C. What will be the final temperature of the mixture? (Assume no heat is lost to the container or the surroundings.)

**__CONSTANTS __** <span style="font-family: OfficinaSerif-Book,serif; font-size: 16pt;">L f <span style="font-family: OfficinaSerif-Book,serif; font-size: 16pt;"> (Gold) = 6.3 x 104 J kg -1 <span style="font-family: OfficinaSerif-Book,serif; font-size: 16pt;">L f <span style="font-family: OfficinaSerif-Book,serif; font-size: 16pt;"> (Copper) = 2.05 x 105 J kg -1 <span style="font-family: OfficinaSerif-Book,serif; font-size: 16pt;">c (Copper) = 390J kg -1 <span style="font-family: OfficinaSerif-Book,serif; font-size: 16pt;">K -1 <span style="font-family: OfficinaSerif-Book,serif; font-size: 16pt;">c (Water) = 4200 J kg -1 <span style="font-family: OfficinaSerif-Book,serif; font-size: 16pt;"> K -1 <span style="font-family: OfficinaSerif-Book,serif; font-size: 16pt;">L f <span style="font-family: OfficinaSerif-Book,serif; font-size: 16pt;"> (Water) = 3.34 x 105 J kg -1