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

Filtration is a technique used to separate an insoluble solid from a liquid, where the solid remains as a residue on the filter paper, and the liquid that passes through is called the filtrate. There are two main methods: using a simple flask and funnel for slower filtration, and employing a vacuum pump with a Büchner funnel for a quicker process, which is also beneficial for re-crystallizing partially dissolved solids. Evaporation, or crystallization, is another separation method where a soluble solid is isolated from a liquid by heating, causing the solvent to vaporize and leaving the solid material behind. These methods are practical for separating components in mixtures, as exemplified by the use of a coffee filter to retain coffee grounds while allowing the liquid coffee to pass through.

Filtration and Evaporation

Everyone saw 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 it's 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 it's termed the residue. So the solid that you get at the end stuck onto the filter paper is called your residue and the solvent passes through. The filter paper is tall. It's 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 hear 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 to 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 flats which will draw out the filtrate faster. Now this is best used if you want 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 though already more dissolved solid.

So both of these options are different types of filtrations that you can use. The first one would be much simpler, build more, 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 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 the separation of a soluble solid from a liquid based on the boiling point of the solvent. So here this is different and 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, this bowl, this is our evaporation bowl or heating bowl. And basically if we heat this enough, we'll be able to evaporate or vaporize the liquid portion and what would 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.

Here’s what students ask on this topic:

What is the difference between filtration and evaporation?

Filtration and evaporation are both separation techniques but serve different purposes. Filtration is used to separate an insoluble solid from a liquid. The solid remains as a residue on the filter paper, while the liquid that passes through is called the filtrate. There are two main methods: using a simple flask and funnel for slower filtration, and employing a vacuum pump with a Büchner funnel for quicker filtration. Evaporation, or crystallization, is used to separate a soluble solid from a liquid by heating. The solvent vaporizes, leaving the solid material behind. This method is useful for isolating components in mixtures where the solid is completely dissolved in the liquid.

How does a vacuum pump aid in the filtration process?

A vacuum pump aids in the filtration process by creating a vacuum within the flask, which helps to draw the filtrate through the filter paper more quickly. This method is particularly useful when dealing with partially dissolved solids, as the vacuum pump decreases the temperature around the Büchner funnel, promoting recrystallization of the dissolved solid. This results in a faster and more efficient separation process compared to simple gravity filtration.

What are some everyday examples of filtration?

Everyday examples of filtration include using a coffee filter in a coffee machine. The coffee filter retains the coffee grounds (residue) while allowing the liquid coffee (filtrate) to pass through. Another example is using a water filter to remove impurities from tap water. The filter traps particles and contaminants, providing clean, filtered water. These examples demonstrate how filtration is used to separate solids from liquids in daily life.

What is the role of filter paper in the filtration process?

Filter paper acts as a semi-permeable membrane in the filtration process. It allows the passage of the liquid (filtrate) while retaining the insoluble solid (residue) on its surface. The filter paper is typically folded to fit within a funnel, ensuring that the liquid can pass through while the solid particles are trapped. This separation technique is essential for isolating components in mixtures where the solid is not dissolved in the liquid.

How does evaporation help in separating a soluble solid from a liquid?

Evaporation, or crystallization, helps in separating a soluble solid from a liquid by heating the mixture. The heat causes the solvent to vaporize, leaving the solid material behind. This method is effective for isolating components in mixtures where the solid is completely dissolved in the liquid. By evaporating the solvent, the solid crystallizes and can be collected, making it a useful technique for separating and purifying substances.