 In looking at observing reactions involving alkanes and alkanes then, one thing is very important. Firstly, the smaller members of each of these groups are gases at room temperature, and therefore they're a little more difficult to study. So we want some longer chain compounds in order for them to at least be liquids at room temperature, so we can see what's happening with them in terms of their density, in terms of their solubility, and also in terms of their reactivity. Two compounds which are relatively similar are hexane and cyclohexane. If we were to briefly draw these, then our hexane would look like this. One, two, three, four, five, six, and hydrogens at each of these points. Cyclohexane, on the other hand, would look like this. Let's just put all of those hydrogens in. Okay, so now all of the hydrogens are in, and you can see both of these two compounds are both alkanes. They both have only single bonds connecting their carbons. They both have six carbons. There is a small difference in the number of hydrogens, and you can see that the hexane is a C6H14 compound, and the cyclohexane is a C6H12 compound. But given the fact that there's only two different hydrogens, is there anything we need to know about these two compounds in terms of safety? Well, a little guide is always one thing that we can look at. So I guess if you see a difference in the fact that hexane is for use only by teachers, and cyclohexane can be used by students, that's already telling you that there must be some difference. So can we see anything listed under the dangers or risks associated with these? Well, the potential hazards is a good place for us to go and have a look at. Either way, we have compounds which are highly flammable. So when we're looking at assessing different compounds for their risks, and the fact that both of these are alkanes, they are highly flammable. And therefore, if we're looking at, say, keeping away from naked flames, that would identify both a risk associated with this particular compound and also some sort of procedure that you could carry out in order to minimize the risks associated with using that. The other thing that you, I guess, need to be aware of is that area of disposal. So you can see for both of these, this one says toxic to aquatic life. This one says very toxic to aquatic life. So that's telling me straight away, don't throw this down the sink. Don't wash my excess down the sink, because that's where it's going to end up. So that means we're going to need to collect the waste from these experiments involving either of these compounds, and we're going to have to dispose of them separately. Usually we collect them with a range of other organic compounds for disposal. And that's because we can't just empty these down the sink. So there are some really useful pieces of information when you start looking at these safety data sheets, which is what SDSs are. They tell us a lot of information about handling, what sort of things we should do. In fact, the first safety measure that you could identify is substitute cyclohexane for hexane in an experiment, because you can still see the reactions that are occurring with an alkane, but you have significantly reduced the risks associated with using these chemicals because you've chosen the safer chemical. So you can see the toxicity that's identified for hexane is not present, and therefore we've already mitigated some of the risks just by not using that particular one. There is an issue with inhaling the vapours for hexane, and so you can see right here in the safety or handling procedures that they actually suggest with cyclohexane that it is a less toxic substitute for hexane or for aromatic solvents. Aromatic solvents is another group that we're not looking at today, so we won't worry about those. But certainly if we were going to choose hexane, the fact that we've chosen cyclohexane instead means we're already dealing with something that is less toxic. Try and get into the habit with each of the chemicals that you look at to at least have a bit of a look at the safety issues around handling and disposal for them, because when you're assessing risks, the more specific you can be about the chemicals you're using, the better the quality of your answer. Thanks for watching.