Just because two compounds have the same melting point does not mean that they exhibit similar interacting characterstics. Melting means that intermolecular bonds that hold molecules together are being broken. Sometimes, when adding impurities into a pure compound, these intermolecular bonds are disturbed by the presence of the impurity. Because of this, the solution will melt at a lower temperature than a pure solid due to disturbed intermolecular bonds (from a solid to another molecule of the same solid) T= H/S Another reason is the change in enthalpy (H) describes the amount of heat required to break the interactions between solid molecules in order to become a liquid. This value does not change much when you add an impurity. The change in entropy (S) describes the entropy gained when going from the much more ordered solid phase to the much less ordered liquid phase. Adding an impurity to the liquid phase increases the entropy of the liquid without affecting the entropy of the solid much; the end result is that S larger for a solid melting into an impure liquid than a pure liquid. Adding an impurity to the liquid phase causes S to increase without changing H. As you can see from the equation above, this situation must cause the melting point (T) to decrease. Therefore, adding an impurity, will cause a substance to melt at a lower temperature. Solution Just because two compounds have the same melting point does not mean that they exhibit similar interacting characterstics. Melting means that intermolecular bonds that hold molecules together are being broken. Sometimes, when adding impurities into a pure compound, these intermolecular bonds are disturbed by the presence of the impurity. Because of this, the solution will melt at a lower temperature than a pure solid due to disturbed intermolecular bonds (from a solid to another molecule of the same solid) T= H/S Another reason is the change in enthalpy (H) describes the amount of heat required to break the interactions between solid molecules in order to become a liquid. This value does not change much when you add an impurity. The change in entropy (S) describes the entropy gained when going from the much more ordered solid phase to the much less ordered liquid phase. Adding an impurity to the liquid phase increases the entropy of the liquid without affecting the entropy of the solid much; the end result is that S larger for a solid melting into an impure liquid than a pure liquid. Adding an impurity to the liquid phase causes S to increase without changing H. As you can see from the equation above, this situation must cause the melting point (T) to decrease. Therefore, adding an impurity, will cause a substance to melt at a lower temperature..

1. Just because two compounds have the same melting point does not mean that they exhibit similar
interacting characterstics. Melting means that intermolecular bonds that hold molecules together
are being broken. Sometimes, when adding impurities into a pure compound, these
intermolecular bonds are disturbed by the presence of the impurity. Because of this, the solution
will melt at a lower temperature than a pure solid due to disturbed intermolecular bonds (from a
solid to another molecule of the same solid)
T= H/S
Another reason is the change in enthalpy (H) describes the amount of heat required to break the
interactions between solid molecules in order to become a liquid. This value does not change
much when you add an impurity. The change in entropy (S) describes the entropy gained when
going from the much more ordered solid phase to the much less ordered liquid phase. Adding an
impurity to the liquid phase increases the entropy of the liquid without affecting the entropy of
the solid much; the end result is that S larger for a solid melting into an impure liquid than a pure
liquid.
Adding an impurity to the liquid phase causes S to increase without changing H. As you can see
from the equation above, this situation must cause the melting point (T) to decrease. Therefore,
adding an impurity, will cause a substance to melt at a lower temperature.
Solution
Just because two compounds have the same melting point does not mean that they exhibit similar
interacting characterstics. Melting means that intermolecular bonds that hold molecules together
are being broken. Sometimes, when adding impurities into a pure compound, these
intermolecular bonds are disturbed by the presence of the impurity. Because of this, the solution
will melt at a lower temperature than a pure solid due to disturbed intermolecular bonds (from a
solid to another molecule of the same solid)
T= H/S
Another reason is the change in enthalpy (H) describes the amount of heat required to break the
interactions between solid molecules in order to become a liquid. This value does not change
much when you add an impurity. The change in entropy (S) describes the entropy gained when

2. going from the much more ordered solid phase to the much less ordered liquid phase. Adding an
impurity to the liquid phase increases the entropy of the liquid without affecting the entropy of
the solid much; the end result is that S larger for a solid melting into an impure liquid than a pure
liquid.
Adding an impurity to the liquid phase causes S to increase without changing H. As you can see
from the equation above, this situation must cause the melting point (T) to decrease. Therefore,
adding an impurity, will cause a substance to melt at a lower temperature.