Boiling water. Image credit chemestryland.com

Boiling water. Image credit chemistryland.com

ZIMSEC O Level Combined Science Notes: Latent Heat

  • when heat is applied to a material the temperature of that material increases
  • if the heat is removed and the material is allowed to cool then there is a decrease in that material’s temperature
  • however when heat results in a change of state there will be no temperature change
  • latent heat is the heat energy used to change to state of the material
  • For example when a block of ice is heated no change in its temperature is observed during the period
  • when it melts as the heat energy is used by the melting ice to change state
  • when water changes into steam it absorbs heat energy and its temperature does not change
  • when a substance changes state from solid to liquid and from liquid to gas it absorbs latent energy during the process
  • latent heat of vapourisation-is the heat energy that is absorbed by a liquid as it changes into a vapour

Cooling curves

The cooling curve of napthalene. Image credit MediaWiki

The cooling curve of naphthalene. Image credit MediaWiki

  • When steam is cooled into condenses into a liquid
  • If the liquid is cooled further it solidifies
  • A cooling curve can be thus obtained
  • This is a reverse of the heating curve
  • As a vapour changes into a liquid it gives out heat which prevents a drop in temperature
  • When the liquid solidifies the temperature remains the same while heat is given out

To access more topics go to the Combined Science Notes page.


Quick NetOne, Telecel, Africom, And Econet Airtime Recharge

If anything goes wrong, chat with us using the chat feature at the bottom right of this screen