What is Centrifugation in Chemistry? Definition, Steps, and Examples
Centrifugation is essential in chemistry and helps students understand various practical and theoretical applications related to this topic. This key separation technique makes it possible to divide mixtures of solids and liquids, or particles of different densities, using the force created by rapid spinning. Centrifugation is used widely in laboratories, the food industry, medical diagnostics, and even in home appliances like washing machines.
What is Centrifugation in Chemistry?
Centrifugation refers to a physical separation technique that uses centrifugal force produced by a spinning apparatus, called a centrifuge, to separate heavier and lighter components within a mixture. This process appears in chapters related to separation of substances, colloids, and suspensions in chemistry, making it a foundational part of your chemistry syllabus.
Molecular Formula and Composition
Centrifugation is a technique, not a chemical compound, so it doesn’t have a molecular formula. Instead, it deals with mixtures—liquids and solids, sometimes called supernatant and pellet—classified under physical separation methods.
Preparation and Synthesis Methods
Centrifugation doesn’t involve chemical synthesis, but it does require correct preparation steps. In a laboratory, to set up centrifugation, you must: 1. Place the sample mixture (such as blood, milk, or muddy water) in special centrifuge tubes. 2. Balance all tubes in the centrifuge (equal mass, not just equal volume). 3. Set the correct speed (measured in rpm or g-force) based on the density and sensitivity of components. 4. Run the centrifuge for a specified time. 5. Remove tubes carefully after the run, keeping tube orientation steady.
Physical Properties of Centrifugation
Centrifugation depends on: - Density differences between components (the bigger the difference, the easier the separation). - Viscosity of the mixture (more viscous = slower separation). - Rotor type (fixed angle, swinging bucket, or vertical). - Speed (rpm) and relative centrifugal force (g-force).
Chemical Properties and Reactions
Centrifugation itself does not cause a chemical reaction. It only accelerates sedimentation, allowing particles or cells to collect (pellet) at the bottom, while lighter components remain in the supernatant. For example, when centrifuging milk, fat globules separate as the cream layer. In DNA extraction, cellular debris pellets at the bottom, and purified DNA stays in solution above.
Frequent Related Errors
- Confusing centrifugation with filtration or sedimentation—the methods and apparatus are different.
- Assuming speed (rpm) alone is enough: g-force and tube balancing are crucial for safety and results.
- Handling only liquids: centrifugation can also separate fine suspended solids from gases (in industry) or remove water from solids (like clothes in a washing machine).
Uses of Centrifugation in Real Life
Centrifugation is widely used in science and daily life. Key applications include:
- Separating plasma from blood cells in medical labs
- Turning whole milk into cream and skimmed milk
- Drying clothes in washing machines
- Clarifying wine and juices by removing suspended particles
- Environmental labs for analyzing pollutants in water
- Purifying DNA, proteins, and viruses for research
Relevance in Competitive Exams
Students preparing for NEET, JEE, and Olympiads should be familiar with centrifugation, as it often appears in both theory-based and practical questions. You might be asked to compare it with filtration or sedimentation, or presented with examples where identifying correct separation techniques is key. Understanding applications and safety steps is also a common exam area.
Relation with Other Chemistry Concepts
Centrifugation is closely related to topics such as physical separation methods and colloids. Knowing how centrifugation differs from filtration, distillation, and other separation techniques helps build strong conceptual foundations and prevents confusion in the exam.
Step-by-Step Reaction Example
Example: Centrifugation of Blood Sample
1. Collect a tube of whole blood.
2. Place the tube in the centrifuge, ensuring it is balanced by placing an equal-mass tube opposite.
3. Set the centrifuge to 1500–2000 g (about 4000 rpm), run for 10 minutes.
4. After stopping, observe two layers: the bottom red pellet of blood cells and the clear plasma above (supernatant).
5. Carefully extract plasma with a pipette, avoiding mixing.
Lab or Experimental Tips
Remember centrifugation by the “spinning-out” rule: heavier substances move outward, lighter ones stay closer to the center. Always balance tubes by mass, not just volume, and keep the lid closed during operation. Vedantu educators suggest visualizing a merry-go-round, as heavier objects get flung further out—making the science easy to imagine and recall.
Try This Yourself
- Explain, in a few sentences, how a washing machine uses centrifugation to dry clothes.
- Compare centrifugation and filtration using actual mixtures (e.g., chalk in water vs. sand in water).
- List two mixtures (besides milk) that can be separated using a centrifuge.
Final Wrap-Up
We explored centrifugation—its definition, operating principle, common uses, and key differences from other techniques. This method is not only critical for laboratories but is a smart example of how science is used in everyday tasks. For more in-depth explanations and exam-prep tips, explore live classes, concept notes, and practical demos on Vedantu.
FAQs on Centrifugation: Principle, Process, Types & Applications
1. What is centrifugation in chemistry?
Centrifugation is a laboratory technique used to separate components of a mixture based on their density. It involves spinning the mixture at high speed in a centrifuge, causing denser components to sediment to the bottom (forming a pellet) while lighter components remain in the supernatant liquid above.
2. What is the principle of centrifugation?
The principle of centrifugation relies on the application of centrifugal force. This force, much stronger than gravity, pushes denser particles outward towards the bottom of the centrifuge tube. Lighter particles, experiencing less force, remain closer to the center or top. The difference in sedimentation rates allows for separation of components.
3. What are the different types of centrifugation?
Several types of centrifugation exist, each suited to different separation needs:
• Differential centrifugation separates based on size and density differences.
• Density gradient centrifugation employs a density gradient to separate based on density.
• Rate-zonal centrifugation separates based on sedimentation rate.
• Isopycnic centrifugation separates components until they reach their equilibrium density in the gradient.
4. What are some examples of centrifugation applications?
Centrifugation has diverse applications:
• Separating blood components (plasma, red blood cells, white blood cells)
• Isolating cream from milk
• Purifying proteins and other biomolecules
• Separating cells from culture media
• Analyzing environmental samples.
5. How does a centrifuge work step-by-step?
The process generally involves:
1. Preparing the sample (e.g., homogenizing tissue).
2. Transferring the sample into centrifuge tubes.
3. Balancing the tubes in the centrifuge rotor (crucial for safety and efficient separation).
4. Setting the centrifuge speed (rpm or g-force) and time.
5. Starting the centrifuge and allowing it to run.
6. Carefully removing the tubes once the run is complete.
7. Separating the supernatant from the pellet.
6. What is the difference between centrifugation and filtration?
Both separate mixtures, but they do so based on different properties:
• Centrifugation separates components by density using centrifugal force.
• Filtration separates components by size using a porous medium. Particles larger than the pore size are retained; smaller ones pass through.
7. What safety precautions should be taken when using a centrifuge?
Always ensure that:
• Tubes are properly balanced.
• The centrifuge lid is securely closed during operation.
• The centrifuge is properly maintained.
• Appropriate safety measures are taken when handling hazardous materials.
8. How are the speed (rpm) and g-force related in centrifugation?
RPM (revolutions per minute) refers to the rotational speed of the centrifuge. G-force (relative centrifugal force) is the measure of centrifugal acceleration experienced by the sample. Higher RPM generally means higher g-force, leading to faster sedimentation. Specific g-force values are often prescribed in protocols for efficient separation.
9. What factors affect the efficiency of centrifugation?
Several factors influence the separation efficiency of centrifugation:
• The difference in density between the components.
• The viscosity of the sample medium.
• The speed (RPM or g-force) of the centrifuge.
• The time of centrifugation.
• The temperature of centrifugation.
10. What are supernatant and pellet in centrifugation?
After centrifugation, the sample separates into two layers:
• The supernatant is the liquid layer above the sediment.
• The pellet is the solid material that has sedimented to the bottom of the tube.
11. How is centrifugation used in DNA extraction?
Centrifugation plays a key role in DNA extraction protocols. It's used to pellet cells or precipitate DNA, separating it from other cellular components. Density gradient centrifugation can also be employed to purify DNA further.
12. What is the role of the centrifuge rotor?
The rotor is the spinning component of the centrifuge that holds the sample tubes. Different types of rotors (e.g., fixed-angle, swing-bucket) exist, each with its advantages depending on the separation technique and the type of sample being processed. The rotor’s design significantly impacts the sedimentation process.
