Worksheet: Specific Latent Heat

In this worksheet, we will practice using the formula E = mL to calculate the amount of energy absorbed or released by a change in the state of a material.

Q1:

1 kg of copper and 1 kg of nickel are both heated continuously at the same rate. Determine which metal will completely melt first. Use a value of 205 kJ/kg for the specific latent heat of fusion of copper and use a value of 297 kJ/kg for the specific latent heat of fusion of nickel.

  • ACopper
  • BNickel

Q2:

Which of the following is the correct unit for the specific latent heat of fusion?

  • AJ/kg
  • B J k g C /
  • CJ⋅kg
  • Dkg/J
  • E J k g C /

Q3:

Water in a pan reaches 100C, but the pan is still left on the heat, so eventually all of the water turns to water vapor. Calculate the energy needed to evaporate the 1.2 kg of water contained by the pan. Use a value of 2,258 kJ/kg for the specific latent heat of vaporization of water. Give your answer to 2 significant figures.

Q4:

Which of the following is the correct formula for the energy required to evaporate a substance? 𝐸 represents the energy required, 𝑚 represents the mass of the substance, 𝐿 represents the specific latent heat of vaporization, 𝑐 represents the specific heat capacity, and Δ𝜃 represents the change in temperature.

  • A 𝐸 = 𝑚 𝐿 Δ 𝜃
  • B 𝐸 = 𝑚 𝑐 Δ 𝜃
  • C 𝐸 = 𝑚 𝐿
  • D 𝐸 = 𝑚 𝐿
  • E 𝐸 = 𝑚 𝑐

Q5:

A 10 g cube of ice at 0C is placed outside in direct sunlight on a hot day. The sunlight and the hot air around the cube heat it at a rate of 10 W. It takes 5.56 minutes for the ice to completely melt. Calculate the specific latent heat of fusion for water. Give your answer to 3 significant figures.

Q6:

565 kJ of energy is used to melt a block of zinc that was already at its melting temperature when the energy was supplied to it. Find the mass of the block of zinc, using a value of 113 kJ/kg for the specific latent heat of fusion of zinc.

Q7:

The table lists the specific latent heat of fusion for various metals. A student has 200 g of an unknown metal. The student heats the metal to its melting point and then measures how much energy is absorbed by the metal for all of it to melt, and gets a value of 79.6 kJ. Which of the four metals listed in the table does the student have?

Metal Aluminum Cobalt Iron Nickel
Specific Latent Heat of Fusion (kJ/kg) 398 276 272 297
  • AAluminum
  • BCobalt
  • CIron
  • DNickel

Q8:

30 g of molten gold is allowed to solidify. It releases 1,890 J of energy to the surrounding environment as it does so. What is the specific latent heat of fusion for gold?

Q9:

A metal at the temperature at which it melts is heated until all of the metal has become liquid. It takes 41 kJ to completely melt the metal, and its mass is 0.2 kg. What is the specific latent heat of fusion of the metal?

Q10:

A substance, which is initially at 20C and solid, is heated. The temperature of the substance is recorded over time, and this data is shown in the graph.

What is the melting point of the substance?

Q11:

A 10 kg block of ice is converted to water vapor. The block of ice starts at 20C; first, it must be completely melted, and then it is heated to 100C. Find the energy required to do this. Use a value of 2,108/JkgC for the specific heat capacity of ice and use a value of 4,184/JkgC for the specific heat capacity of water. Use a value of 334 kJ/kg for the latent heat of fusion of water and use a value of 2,258 kJ/kg for the latent heat of vaporization of water. Give your answer to 3 significant figures.

Q12:

A pan is filled with 2 kg of water at a temperature of 100C. If the pan can transfer energy to the water at a rate of 2.5 kW, determine how many minutes it will take to vaporize all of the water in the pan. Use a value of 2,258 kJ/kg for the specific latent heat of vaporization of water. Give your answer to the nearest minute.

Q13:

A forge can transfer 200 kJ of energy to a metal to heat it before running out of fuel. Bars of silver or gold can be placed in the forge to melt them. If the metal to be melted is already at its melting temperature when placed in the forge, determine how much more gold than silver the forge can melt before running out of fuel. Use a value of 63 kJ/kg for the specific latent heat of fusion of gold and use a value of 111 kJ/kg for the specific latent heat of fusion for silver. Give your answer to 2 significant figures.

Q14:

Determine how much energy is needed to melt 2 kg of ice. Use a value of 334 kJ/kg for the specific latent heat of fusion of ice.

Q15:

A substance, which is initially at 140C and is liquid, is allowed to cool. The temperature of the substance is recorded over time, and this data is shown in the graph. What is the melting point of the substance?

Q16:

Which of the following is the correct formula for the energy required to melt a substance? 𝐸 represents the energy required, 𝑚 represents the mass of the substance, and 𝐿 represents the specific latent heat of fusion.

  • A 𝐸 = 𝑚 + 𝐿
  • B 𝐸 = 𝑚 𝐿
  • C 𝐸 = 𝑚 𝐿
  • D 𝐸 = 𝑚 𝐿
  • E 𝐸 = 𝑚 𝐿

Q17:

A substance, which is initially at 90C and is liquid, is heated. The temperature of the substance is recorded over time, and this data is shown in the graph. What is the boiling point of the substance?

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