Filtration and Evaporation - Online Tutor, Practice Problems & Exam Prep

Filtration and Evaporation

Hey everyone, so in the first part of this video let's talk about filtration. Now filtration is just the process of separating out a solid from a liquid. So here we're going to say the technique involves the separation of an insoluble solid from a liquid by its moving through a filter. So we're going to be using filter paper in terms of filtration. Now, here we're going to say that the insoluble solid is left behind on the filter paper and is termed the residue. So, that solid that you get at the end stuck onto the filter paper is called your residue. And the solvent that passes through the filter paper is termed the filtrate. So here we have two examples of filtration. Both of them deal with using an Erlenmeyer flask, so both of them have this flask involved. In the first one, we're using a simple Erlenmeyer flask, and we're going to use a funnel. Within this funnel, we have our filter paper that has been folded in order to fit properly within this funnel. This filter paper kind of serves as a semi-permeable membrane. It allows the passage of our solvent or filtrate through, and then the solid actually can't pass through and it's stuck on the residue paper on the filter paper. So the residue will adhere itself to this. Now this method is a little bit time-consuming. It takes a good amount of time. It works best if your solid is really not that dissolved within your solution. Now the second type of filtration we can have here involves a different type of flask. Here it has a vacuum pump that can be attached to it. This vacuum pump can help rush the filtrate faster through the filter paper. We're using a Buchner funnel, and of course, we still have our filter paper here where our solid can adhere to it. Now the vacuum pump's going to pull on basically cause a vacuum within our flaps, which will draw out the filtrate faster. Now this is best used if you, 1, want to do this process faster, and also it works best if your solid is more partially dissolved because by using the vacuum pump it's actually going to decrease the temperature around the Buchner funnel. This drop in temperature will help to recrystallize the already more dissolved solid. So both of these options are different types of filtration that you can use. The first one being much simpler, the other one requiring a few more parts to it. Now a great example of everyday use of filtration involves a coffee filter. So when you put a coffee filter within your coffee machine, what does it do? It allows the coffee bean grinds or residues to remain behind with on the coffee filter, and then the filtrate, which in this case is your coffee, filters through. Now that we've talked about filtration, let's look at evaporation. So evaporation, sometimes called crystallization, this is the technique involved in the separation of a soluble solid from a liquid based on the boiling point of the solvent. So here this is different. In the other ones, we had insoluble solids or solids that were a little bit more soluble. Here it's completely soluble and here we have a Bunsen burner, and what we have here in this bowl, this is our evaporation bowl or heating bowl. And basically, if we heat this up enough, we'll be able to evaporate or vaporize the liquid portion, and what will be left behind at the end are pieces of solid material. So both of these techniques, filtration, and evaporation, are just useful ways in which we can separate our liquid from our solid within a given mixture.