 Okay, so let's have a look at the properties of alcohols. The alcohol functional group consists of an oxygen atom and a hydrogen atom. As you know, the oxygen atom is very electronegative and the hydrogen is not, and this is the basis for the polarity of water. The same situation exists in alcohols. So let me draw out ethanol. Even though the hydrocarbon part of an alcohol molecule is non-polar, if you recall the CH3-CH2, that's going to be non-polar like any other hydrocarbon. However, the OH part of the molecule is very polar, which gives the molecule an overall molecular dipole. And it also means that then alcohol molecule can form hydrogen bonds. So I'll draw another methanol molecule over here like this. Then it's possible for hydrogen bonding to occur between say the oxygen of one molecule and the hydrogen of another or the hydrogen of one molecule and the oxygen of another because the oxygens have that little delta negative charge and the hydrogens have that little delta positive charge and they attract each other. It also means that the alcohol molecules could form hydrogen bonds with water because, as you know very well, the structure of water also has the delta negative on the oxygen and the delta positive on the hydrogens. So if an alcohol molecule comes into contact with water, it's able to form hydrogen bonds with it as well. Now there are several important consequences that follow from this polarity. First of all, alcohols have a higher boiling point than alkanes that have the same number of carbons in them. This is because the hydrogen bonding is stronger and so it requires more energy to separate the molecules. It also means that they have a greater solubility in water than the corresponding alkanes and this has to do with hydrogen bonding as well. And it means that the alcohols are a polar solvent and are able to dissolve a wide range of substances. So let's look at this in a bit more detail. You already know that the trend in boiling points is that as the molecule gets bigger, the boiling point increases. Do you remember why? The larger the molecule, the greater the van der Waals forces that stick the neighbouring molecules together. So on this little table here, we could say that as we go in this direction, you can see that the molecules are getting bigger. So that means greater size, greater boiling point because of van der Waals. However, it is also possible for a molecule to engage in more than one kind of intermolecular bonding. So every molecule has van der Waals forces, but if a molecule additionally has some kind of dipole, it can also engage in dipole-dipole attractions or in hydrogen bonds. And this is the case with alcohols. So the hydrocarbon part of an alcohol molecule is largely non-polar, as we said, and it engages in van der Waals attractions. But the OH group is highly polar and it's able to take part in hydrogen bonding. So this means that neighbouring alcohol molecules can form hydrogen bonds between their OH groups, which increases the energy and therefore the temperature required to separate the molecules from each other and evaporate as a gas. So you can see that if you compare an alkane with an alcohol, so let's take propane here and propanol here, the alcohol has a much higher boiling point because it can hydrogen bond. However, the other trend is also obvious. All of the alcohols in this yellow row have only one OH group, so the amount of hydrogen bonding should remain roughly constant. However, the boiling point still increases as the carbon chain gets longer, showing that the increase in van der Waals forces still has a significant effect. The bottom row on this table gives you a peek ahead to the carboxylic acids and it's worth mentioning here because it reinforces both of these trends. A carboxylic acid can hydrogen bond both from its double bonded oxygen here and also from the OH group. So a propanoic acid molecule like this one can form more hydrogen bonds than say propanol can. So as you increase the amount of hydrogen bonding that can form, you also increase the boiling point. It follows then that carboxylic acids have even higher boiling points than the corresponding alcohols and they also show the increasing boiling point as the hydrocarbon chain gets longer.