P1.2.4 - Specific latent heat

• Q1.

  You need to heat or cool a substance to produce a change of state.

  
• Q2.

  When you melt ice or boil water there is no temperature rise. The internal energy is increasing even though the temperature is not . The energy that is transferred is breaking the attractive forces between the water molecules
• Q3.What is specific latent heat of fusion ( melting)

  Its the energy transferred when 1kg of a substance changes from the solid state to the liquid state or from the liquid state to the solid state
• Q4. What is specific latent heat of vaporisation?

  The energy transferred when 1kg of a substance changes from liquid to gas.
• Q5.How do you calculate with specific latent heat?

  Thermal energy for a change in state(J) = Mass(kg) x specific latent heat (J/kg)
• Q6.Calculate the energy you need to transfer to melt an ice cube at 0 degrees with a mass of 25.0g. the latent heat of fusion is 334 kj/kg

  Step 1 : write what you know

  mass = 0.25g= 0.025kg

  specific latent heat of fusion = 334kj/kg=334000J/kg

  step 2 : put numbers into equation

  0.025 x 340000 = 8350J (3 sig fig)
• How is specific latent heat different from specific heat capacity ?

  Specific latent heat: heat required to change the state of a substance without a change in temperature. Specific heat capacity: heat required to change the temperature of a substance by 1 degree Celsius.