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

Filtration is the process of separating an insoluble solid from a liquid using a filter, where the solid remains on the filter paper (residue) and the liquid that passes through is called the filtrate. Two methods include simple filtration with an Erlenmeyer flask and funnel, and vacuum filtration using a Buckner funnel, which speeds up the process. Evaporation, or crystallization, separates a soluble solid from a liquid by heating, leaving solid material behind. Both techniques are essential for separating mixtures in chemistry.

Filtration-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. Here we say the technique involves the separation of an insoluble solid from a liquid as it moves through a filter. We're going to be using filter paper for this process. Here the insoluble solid is left behind on the filter paper and is termed the residue.

So the 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. Here we have two examples of filtration, both involving an Erlenmeyer flask. In the first one, we're using a simple Erlenmeyer flask and a funnel. Within this funnel, we have our filter paper that has been folded to fit properly. This filter paper acts as a semi-permeable membrane, allowing the passage of our solvent or filtrate through, while the solid can't pass through and is stuck on the filter paper.

This method is a bit time-consuming. It works best if your solid is not that dissolved in your solution. The second type of filtration involves a different type of flask. Here it has a vacuum pump that can be attached. This vacuum pump helps rush the filtrate faster through the filter paper. We're using a Buchner funnel, and our solid can adhere to the filter paper here. The vacuum pump creates a vacuum within our flask, which draws out the filtrate faster. This method is best used if you want to process faster, and it also works best if your solid is more partially dissolved. Using the vacuum pump decreases the temperature around the Buchner funnel, which helps recrystallize the already more dissolved solid.

Both of these options offer different methods of filtration that you can use. The first one is much simpler, while the other one requires a few more components. A great example of everyday filtration involves a coffee filter. Within your coffee machine, the coffee filter allows the coffee bean grinds or residues to remain on the coffee filter, while the filtrate, in this case, your coffee, filters through.

Now that we've discussed filtration, let's look at evaporation, sometimes called crystallization. This technique involves the separation of a soluble solid from a liquid based on the boiling point of the solvent. In this scenario, the solid is completely soluble. We use a Bunsen burner and an evaporation bowl or heating bowl. By heating this sufficiently, we can evaporate or vaporize the liquid portion, and what is left behind at the end are pieces of solid material. Both of these techniques, filtration and evaporation, are useful methods for separating 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 in chemistry?

Filtration and evaporation are both separation techniques used in chemistry, but they serve different purposes. Filtration separates an insoluble solid from a liquid using a filter. The solid left on the filter paper is called the residue, and the liquid that passes through is the filtrate. Evaporation, or crystallization, separates a soluble solid from a liquid by heating the mixture. The liquid evaporates, leaving the solid material behind. Filtration is useful for mixtures where the solid does not dissolve in the liquid, while evaporation is used when the solid is dissolved in the liquid.

How does vacuum filtration differ from simple filtration?

Vacuum filtration and simple filtration are two methods of separating an insoluble solid from a liquid. Simple filtration uses a funnel and filter paper placed in an Erlenmeyer flask. The liquid passes through the filter paper, leaving the solid residue behind. This method is time-consuming. Vacuum filtration, on the other hand, uses a Buckner funnel and a vacuum pump attached to the flask. The vacuum pump creates a pressure difference, speeding up the filtration process. This method is faster and more efficient, especially for partially dissolved solids, as the vacuum can help recrystallize the solid by lowering the temperature around the funnel.

What are some everyday examples of filtration?

Filtration is a common process in everyday life. One of the most familiar examples is using a coffee filter in a coffee machine. The coffee filter allows the liquid coffee to pass through while retaining the coffee grounds, which act as the residue. Another example is air filtration in HVAC systems, where air filters trap dust and other particles, allowing clean air to circulate. Water filtration systems also use this principle to remove impurities from water, ensuring it is safe for drinking.

What equipment is needed for evaporation in a chemistry lab?

To perform evaporation in a chemistry lab, you need several pieces of equipment. The primary items include a Bunsen burner for heating, an evaporation bowl or heating dish to hold the liquid mixture, and a tripod or stand to support the bowl above the burner. Additionally, a wire gauze may be used to distribute heat evenly. As the mixture is heated, the solvent evaporates, leaving the soluble solid behind. This method is particularly useful for separating a dissolved solid from its solvent based on their boiling points.

Why is filter paper used in filtration?

Filter paper is used in filtration because it acts as a semi-permeable membrane, allowing the liquid (filtrate) to pass through while retaining the solid particles (residue). The paper's porous structure traps the solid particles, preventing them from passing through with the liquid. This makes filter paper an essential component in separating insoluble solids from liquids in various chemical processes. Its effectiveness depends on the pore size, which can be selected based on the size of the particles being filtered.