Experimental Questions 1. Which types of compounds have the strongest intermolecular forces? How can certain physical properties give an indication of the strength of intermolecular forces of compounds? 2. 3. Relate molecular polarity to the intermolecular forces of the molecule. 4. Relate intermolecular forces of the molecule to physical properties such as evaporation and viscosity. Solution 1. The strongest intermolecular force is hydrogen bonding. Thus the compounds that can form H- bonds each other have the strongest intermolecular forces. 2. When intermolecular forces increases the molecules fells greater attraction among themselves. This means we have to supply more energy to separate them. This result in higher in the physical property. Thus if stronger intermolecular forces are existing we can expect that boiling point , melting point for that sample will increase. Again in case of freezing we have to restrict the movements of the molecules.Thus when stronger forces are there there are already some restriction in the movements and so freezing point is higher. In other words we can say that molecules where there is lower intermolecular forces we have to lower the temperature more to freeze it. 3. When polarity of the molecules increases this gives greater intermolecular forces and thus higher physical properties. This is because each molecular dipole allign themselves with others in such. a way that (+)vely charged part attract the (-)vely charged part and this result long range intermolecular forces. This gives higher intermolecular forces. 4. Evaporation means escape of molecules from the liquis phase. When there is strong intermolecular force exists this means the molecules attract each other more. Thus escape from liquid phase is less. But when intermolecular force is weaker then molecules can escape easily. This means lower the intermolecular force higher the evaporation rate. Again Viscosity is the resistance of a liquid to flow. When attraction is more among the molecules they resist the flow of other molecules. This implies higher viscosity. For example ethanol , CH3CH2OH, has the viscosity 1.07 mPa.s and ethylene glycol, HOCH2CH2OH , has 16.2 mPa.s. We can see that in case of ethanol there is only one OH group. But in case of ethylene glycol there is 2 OH group that can form strong H bonding. This results higher attraction among ethylene glycol moecules and so higher viscosity. .

1. Experimental Questions 1. Which types of compounds have the strongest intermolecular forces?
How can certain physical properties give an indication of the strength of intermolecular forces of
compounds? 2. 3. Relate molecular polarity to the intermolecular forces of the molecule. 4.
Relate intermolecular forces of the molecule to physical properties such as evaporation and
viscosity.
Solution
1. The strongest intermolecular force is hydrogen bonding. Thus the compounds that can form H-
bonds each other have the strongest intermolecular forces.
2. When intermolecular forces increases the molecules fells greater attraction among themselves.
This means we have to supply more energy to separate them. This result in higher in the physical
property. Thus if stronger intermolecular forces are existing we can expect that boiling point ,
melting point for that sample will increase. Again in case of freezing we have to restrict the
movements of the molecules.Thus when stronger forces are there there are already some
restriction in the movements and so freezing point is higher. In other words we can say that
molecules where there is lower intermolecular forces we have to lower the temperature more to
freeze it.
3. When polarity of the molecules increases this gives greater intermolecular forces and thus
higher physical properties. This is because each molecular dipole allign themselves with others
in such. a way that
(+)vely charged part attract the (-)vely charged part and this result long range intermolecular
forces. This gives higher intermolecular forces.
4. Evaporation means escape of molecules from the liquis phase. When there is strong
intermolecular force exists this means the molecules attract each other more. Thus escape from
liquid phase is less. But when intermolecular force is weaker then molecules can escape easily.
This means lower the intermolecular force higher the evaporation rate.
Again Viscosity is the resistance of a liquid to flow. When attraction is more among the
molecules they resist the flow of other molecules. This implies higher viscosity. For example
ethanol , CH3CH2OH, has the viscosity 1.07 mPa.s and ethylene glycol, HOCH2CH2OH , has
16.2 mPa.s. We can see that in case of ethanol there is only one OH group. But in case of

2. ethylene glycol there is 2 OH group that can form strong H bonding. This results higher
attraction among ethylene glycol moecules and so higher viscosity.