This lab shows the temperature change when alkane and alcohol substances are evaporated. The endothermic process, evaporation, occurs when a substance changes from the liquid to the gas phase. The magnitude of the temperature change can be predicted by studying the intermolecular forces of attraction of the alkanes and alcohols used. All substances used contain dipole dipole forces, but the alcohols used contain hydrogen bonding. Hydrogen bonding occurs when hydrogen atoms bond to highly electronegative atoms(nitrogen, oxygen, and fluorine). These bonds are stronger because of the great polarity of the bond and the close approach of the dipoles. The substances with higher intermolecular forces should require more energy to change to a gas. Therefore the higher the intermolecular forces the greater the temperature decrease will be.
1) Why is hydrogen bonding stronger than other types of bonding(London Dispersion Forces and dipole-dipole forces)?
2) Which substance used had the highest intermolecular forces and which substance had the lowest intermolecular forces? Use your knowledge of bonding and lab results to explain this.
3) Explain Delta T(t1-t2) in terms of intermolecular forces.
4) If you don't have the required substances in the lab, could you substitute others? For example, if you dont have 1-Propanol and n-pentane what else can you use?