Centrifugation

Centrifugation as technique for separating mixtures

Science Grade 6

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​Objectives

• Understand and describe the centrifugation method.

• Demonstrate the process of centrifugation to separate components of a mixture.

Reviewing previous lesson

Multiple Choice

The evaporation technique is most effective for separating:

• • A) A gas from a gas.

• • B) A solid from a solid.

• • C) A solid dissolved in a liquid.

• • D) A liquid from a liquid with similar boiling points.

Multiple Choice

1. In which of the following scenarios is the evaporation technique commonly used?

• • A) Separating sand from gravel.

• • B) Obtaining drinking water from seawater.

• • C) Separating butter from milk.

• • D) Removing pebbles from sand.

Multiple Choice

1. What happens to the solvent in a solution during evaporation?

• • • A) It condenses at the bottom of the container.

• • B) It gets absorbed by the solute.

• • C) It turns into a gas and disperses into the air.

• • D) It remains mixed with the solute.

Multiple Choice

1. Why is the evaporation technique sometimes considered a slower method of separation?

• A) Because it requires a magnet.

• • B) Because it relies on the natural process of liquid turning to gas, which can be time-consuming.

• C) Because it requires a filter.

• • D) Because all components mix again after evaporation.

Multiple Choice

1. Which factor can speed up the evaporation process?

• 1. • A) Keeping the mixture in a closed container.

• • B) Decreasing the surface area of the mixture.

• C) Cooling the mixture.

• • D) Increasing the temperature of the mixture.

Open Ended

How you may attempt to clear this mixture?

Watch this video

Open Ended

WHAT IS CENTRIFUGATION?

One can easily observe centrifugal force in real life by tying a stone to a thread and swirling it around. While performing this experiment, a force is felt on the stone that tends to move it away from the center. This force is called the centrifugal force.

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​A Stone Tied to a Thread

The children playing on a merry-go-round ride experience an outward force that tends to throw them on the outer side. This force grows intense upon increasing the speed of rotation. If the safety precautions are not met properly, this centrifugal force might lead to accidents.

​Merry-Go-Round

The centrifugal pumps are the most preferred systems in hydraulics. It consists of an impeller, which is thoroughly immersed in water. When the impeller rotates, the fluid present around it also rotates. While the water undergoes rotation, it encounters centrifugal force because the water is thrown to the outward side. This causes pressure and kinetic energy to rise. Low pressure is developed at the center of the rotating impeller blades. Therefore, the water from the container is easily drawn out.

​Centrifugal Pumps

The rotating mechanism of the machine is responsible to push the clothes, water, and dirt particles to the outer side of the drum. This dirt then gets collected in the pouch attached to the inner side of the container. Hence, the clothes get cleaned properly.

​Washing Machine

A swinging fair ride consist of a huge rotating head pivoted on a cylindrical pole. A number of swings are attached to the base of the rotating head. When this arrangement is subjected to rotational motion, the swings attached to the bottom of the ride move away from the center. This creates a fancy and thrilling motion in the attached swings, leading to an adventurous ride.

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​Swinging Fair Ride

The planets moving around the sun maintain their rotational motion and do not fall in the center. This is because a significant amount of centrifugal force is experienced by all the celestial bodies that are revolving around the sun. Hence, centrifugal force is important in maintaining the planetary orbits. This phenomenon is also responsible to suggest the notion of expansion of the universe and the story of its origin.

​Planetary Orbits 

Making generalizations and abstractions

• ​The method chosen to separate mixtures largely depends on the type and properties of the mixture.

• Centrifugation is particularly useful for mixtures with fine particles that don't easily settle.

Multiple Choice

1. What is the primary principle behind the centrifugation technique?

• • A) Attraction of magnetic substances.

• • B) Settling of substances based on density differences.

• • C) Rapid spinning to separate substances based on their densities.

• • D) Heating a solution to separate it into its components.

Multiple Choice

1. In which of the following scenarios would centrifugation be most appropriate?

• • A) Separating salt dissolved in water.

• • B) Separating iron filings from sand.

• • C) Separating chalk powder from water.

• • D) Separating plasma from blood cells in a blood sample.

Multiple Choice

1. Why might centrifugation be preferred over decantation when dealing with tiny, suspended particles in a liquid?

• • A) Because it uses heat to separate particles.

• • B) Because the spinning action causes denser particles to settle rapidly at the bottom.

• • C) Because it attracts magnetic particles.

• • D) Because it uses a filter to trap particles.

Multiple Choice

1. What happens to the denser components in a mixture during centrifugation?

• • A) They float to the top.

• • B) They remain suspended in the middle.

• • C) They gather at the center of the centrifuge.

• • D) They are pushed outward and settle at the bottom.

Multiple Choice

1. Centrifugation is often used in laboratories to separate:

• • A) Gases from gases.

• • B) Solids from liquids where the solid particles are very small.

• • C) Two solids based on color differences.

• • D) Liquids with different boiling points.

Open Ended

Scenario:

Your school's cafeteria regularly produces a large amount of orange juice using fresh oranges. However, many students have been complaining about the pulp in the juice. The school management has decided to address this issue by removing the pulp to produce clearer juice. They have set up a team to find a solution, and you are a part of it.

Prompt:

Write an essay detailing how you would use the centrifugation technique to separate the pulp from the orange juice. In your essay, ensure to:

1. Define and explain the principle behind centrifugation.

2. Describe a step-by-step process on how you would set up and carry out the centrifugation to achieve the desired result.

3. Discuss the potential advantages of using centrifugation for this purpose compared to simply letting the pulp settle at the bottom over time.

4. Reflect on the importance of this process in ensuring the students' satisfaction and improving the quality of beverages in the cafeteria.