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6 Organic Chemistry Lab Techniques Your Students Should Know

Teaching with Labster
Chemistry

If you’re teaching a course in organic chemistry, perhaps you’re looking for resources to help you introduce or reinforce fundamental lab techniques that every student needs to learn. We’ve identified 6 core techniques that are the first ones you’ll learn in the classroom. We asked our Higher Education Product Manager why each one is important. 

We’ve also identified 6 Labster virtual labs that help you teach each of these techniques. Not only can your students learn the methods, but they can also have fun along the way!

  1. Chromatography

  2. Extraction

  3. Distillation

  4. Recrystallization

  5. Sublimation

  6. Melting point

1. Chromatography

What is Chromatography? A technique that separates molecules in a solution based on how easily they can diffuse and move through a porous matrix of a chromatography plate. Remember the experiment you did as a child dotting ink on paper and then dipping it in water to see the colors run away from the bottom? Thin layer chromatography is an advanced version of this beautiful technique. 

Why is Chromatography important? Sometimes we want to monitor the conversion of one chemical to another during a reaction that takes a long time. By sampling the reaction mixture and analyzing it on a TLC plate, we can check to see if our chemical reaction is complete. This helps us ensure our experiments are accurate, safe, and reproducible.  

Our virtual lab that teaches chromatography is: 

Chromatography: Thin Layer Chromatography: Separate a mixture and monitor a reaction's progress

Discover the intermolecular interactions involved in Thin Layer Chromatography. Utilize this newfound knowledge to assemble, run, and analyze a TLC experiment to monitor the progress of a reaction.

Chromatography

2. Extraction

What is Extraction? We use this technique to separate dissolved molecules or ions (‘a solute’) by moving them from one solvent to another. For example, liquid-liquid extraction relies on solutes having different solubility properties. Imagine you have an aqueous solution containing two different solutes, but only one of those solutes is also soluble in an organic solvent. By mixing the two-solute solution with an immiscible liquid that the targeted solute also is soluble in and allowing the two solvents to separate into layers, we can move or ‘partition’ one of the solutes into a separate solute layer and siphon it off. 

Why is Extraction important? Chemistry is a messy science and often we need to clean up solutions that contain contaminants or purify a synthesized chemical from any leftover reagents or byproducts. Liquid-liquid extraction is a common technique that can help us along the path to chemical purity. 

Our virtual lab that teaches extraction is: 

Liquid-liquid Extraction: Extract caffeine from your everyday drinks

Learn how to use a separating funnel to extract and dry a water-soluble compound, such as caffeine from tea or coffee. If you’ve ever made a mistake in the lab, this virtual lab has your back. Learn how to use a separatory funnel without fear of messing things up. In our simulations, you have the freedom to make mistakes and learn from them as you go.

Liquid extraction

3. Distillation

What is Distillation? Like liquid-liquid extraction, distillation is a separation technique that allows us to separate components of a solution. Distillation relies on components of a solution having different boiling points. For example, ethanol and water are miscible, meaning they dissolve in each other. The boiling point of water is 30°C / 39.9°F higher than ethanol. We can exploit this difference by heating up a solution of ethanol and water to a point where ethanol transitions to the gaseous phase, but water does not. By capturing the ethanol vapor and condensing it back to a liquid, we can successfully separate the two components.

Why is Distillation important? Distillation is a useful technique when there is a need to remove a liquid with a relatively low boiling point from a mixture or solution of multiple components. It is a very common process used industrially to produce food and beverage products, especially to purify products of fermentation processes, like alcohol. 

Our virtual lab that teaches distillation is: 

Simple Distillation: Recycle waste from biodiesel production

In this simulation, your mission is to use the distillation technique to separate and recycle the waste compounds generated by the production of biodiesel from algae (water, glycerol, and methanol) so they can be reutilized for your colony on Mars! Labster utilizes fun storylines to teach important chemistry lab techniques like distillation.

Distillation

4. Recrystallization

What is Recrystallization? Recrystallization is another purification and separation technique that relies on the temperature-dependent solubility profiles of target chemicals to purify solid compounds. The solubility of a compound in a given solvent changes depending on the temperature of that solvent. Think about how much easier it is to dissolve a teaspoon of sugar in a hot drink than in an iced one - the hot temperature of the solvent increases the ability of the solute to dissolve.

In recrystallization, we exploit this property by first dissolving an impure solid in a hot solvent to create a very concentrated solution, then letting the liquid cool down. As the temperature drops, the target compound cannot remain in the solution. The target compound then drops out of the solution or ‘precipitates’ forming pure crystals. If you’ve ever made very concentrated sugar syrup and found crystals at the bottom of the pan once the syrup has cooled, then you too have purified glucose by recrystallization. 

Why is Recrystallization important? Many compounds are solid at room temperature and are mined in an impure form (like rock salt, for example). Recrystallization is a useful technique to refine and purify target chemicals so that they can be put to further use.  

Our virtual lab that teaches recrystallization is: 

Recrystallization: Dissolve your solid and precipitate your crystals

In this simulation, you will learn what are the steps to follow in order to dissolve a solid and recrystallize it to eliminate impurities. You will learn why it is important to choose the right solvent and which are the best ways to recrystallize your solid. Slip on your thermal-resistant gloves, and let's get started! 

Recrystalllization

5. Sublimation

What is Sublimation? Sublimation is a less common phase change process when a substance transitions from its solid state directly to a gaseous state without first becoming liquid. Sublimation is much less common than other phase changes such as melting (solid to liquid) or evaporation (liquid to gas). The sublimation process can be exploited as a purification technique. If the conditions for a target substance to go through sublimation are dissimilar enough from the impurities that contaminate a solid substance, then the target compound can be sublimated and subsequently condensed back to solid on another, typically cooler surface. This results in a purified target substance on one surface with contaminants left behind on the original surface. 

Why is Sublimation important? Sublimation, as a process, has many important applications including the purification of contaminated solid compounds. Sublimation can also be used to ensure the deposition or coating of surfaces with very pure layers of the target compound, for example in the manufacture of small and expensive electronic components. 

Our virtual lab that teaches sublimation is: 

Matter and Phase Changes: Distil ethanol

Rescue a town from a fuel crisis by using your knowledge about matter and phase changes principles and performing ethanol distillation. You’ll learn all the main phase changes, including sublimation.

Distil ethanol

6. Melting point

What is a Melting Point? The melting point of a substance is the temperature at which a pure substance transitions from the solid to the liquid state. When all other factors are constant (especially the atmospheric pressure), the melting point of a pure substance is constant and very precise, much like a compound's boiling or freezing point. 

Why is Melting Point important? When a substance is in its solid form, it is interactions between individual atoms, ions, or molecules that hold the solid mass together. When the substance is pure, these interactions are predictable and constant, meaning that the point at which these interactions break down (and the substance melts) is also predictable and constant. When a substance is impure, the contaminants interfere with these interactions, typically weakening the structure of the solid mass. This disruption leads to a decrease in the melting point, as less energy is required for the solid to transition to the liquid state.

We can exploit this observation in melting point lowering or ‘depression’ to determine if a substance is pure or not; if the solid melts at a temperature lower than expected, we know there’s something contaminating it. 

Our virtual lab that teaches melting point is: 

Melting Point Analysis: Pure or impure?

Learn the techniques and application of melting point analysis and substance purity graphs. Explore the application of the technique in organic syntheses when determining the purity of a solid organic compound.

Heat chamber

Wrap-up of techniques

In summary, here are the 6 organic chemistry lab techniques and their accompanying virtual labs:

  1. Chromatography: Thin Layer Chromatography: Separate a mixture and monitor a reaction's progress

  2. Extraction: Liquid-liquid Extraction: Extract caffeine from your everyday drinks

  3. Distillation: Simple Distillation: Recycle waste from biodiesel production

  4. Recrystallization: Recrystallization: Dissolve your solid and precipitate your crystals

  5. Sublimation: Matter and Phase Changes: Distil ethanol

  6. Melting point: Melting Point Analysis: Pure or impure?

Questions to think about:

  • How could you incorporate these labs into your teaching plans?

  • Are these labs better as self-paced homework assignments or small-group collaboration in class?

Interested in these labs? Try them for 30 days with our all-access pass to Labster’s full catalog of virtual labs, including these organic chemistry labs!