How to Separate Cream from milk?

As we look at our surroundings, we see many things with different shapes, sizes and textures. Everything in this universe is made up of material which scientists call matter. The air we breathe, the food we eat, stones, clouds, stars, plants and animals, even a small drop of water or a particle of sand – everything is matter. These substances have different natures, different properties. They can be pure or there can be some impurities in them. We can also see as we look around that all the things mentioned above occupy space and have mass. 

Techniques to Separate a mixture

Heterogeneous mixtures can be separated into their respective constituents by simple physical methods like handpicking, sieving, filtration that we use in our day-to-day life. Sometimes special techniques have to be used for the separation of the components of a mixture. Some of these techniques are-

1. Centrifugation
2. Evaporation
3. Sublimation
4. Chromatography
5. Distillation and Fraction Distillation

Separation of cream from milk by Centrifugation

An emulsion is a colloid of two or more immiscible liquids where one liquid contains a dispersion of the other liquids. The centrifugation process is used to separate cream from milk. 

Emulsification is the process of mixing two immiscible liquids to form an emulsion and demulsification is the process of breaking the emulsion solution. Demulsification is the process of breaking oil in an emulsion solution. It separates the oil part from the aqueous part in a mixture.

As milk is a suspension mixture of cream in a watery liquid, centrifugation is used to separate cream from milk. Milk is put in a closed container in a big centrifuge machine and the container is spun at a very high speed. The centrifugal forces act on milk and separate the mixture into a cream that is lighter thus floats on top and skimmed milk which is at the bottom. Then cream can be separated from the milk.

Principles of Centrifugation

1. In a solution, particles whose density is higher than that of the solvent sink, and particles that are lighter float to the top.
2. The greater the difference in density, the faster they move.
3. To take advantage of even tiny differences in density to separate various particles in a solution, gravity can be replaced with the much more powerful centrifugal force provided by a centrifuge.
4. A centrifuge is equipment that puts an object in rotation around a fixed axis, applying a strong force perpendicular to the axis of spin.
5. The centrifuge works using the sedimentation principle, where the centripetal acceleration causes denser substances and particles to move outward in the radial direction.
6. Objects that are less dense are displaced and move to the centre.

Process of Centrifugation for separating cream from milk

A separator is a centrifugal device that separates milk into cream and skimmed milk.  Milk is a suspension of tiny droplets of oil in a liquid. The milk is put in a closed container in a big centrifuge machine. When the machine is switched on, the milk is spun at a very high-speed container Due to this the milk separates into cream and skimmed milk. The cream, being lighter, floats over the skimmed milk. It can then be removed. Thus, the cream is separated from milk by centrifugation.

Applications of Centrifugation

1. To separate two miscible substances
2. Fractionation of subcellular organelles.
3. Separating chalk powder from water
4. Removing fat from milk to produce skimmed milk
5. The clarification and stabilization of wine
6. Separation of urine components and blood components in forensic and research laboratories
7. Aids in the separation of proteins using purification techniques such as salting out, e.g. ammonium sulfate precipitation.

Sample Problems

Problem 1: What are some applications of centrifugation?

Solution: 

Some applications are-

1. To separate two miscible substances
2. Fractionation of subcellular organelles.
3. Separating chalk powder from water
4. Removing fat from milk to produce skimmed milk
5. The clarification and stabilization of wine

Problem 2: What are some methods by which heterogeneous mixtures can be separated?

Solution: 

Heterogeneous mixtures can be separated into their respective constituents by simple physical methods like handpicking, sieving, filtration that we use in our day-to-day life. Sometimes special techniques have to be used for the separation of the components of a mixture. Some of these techniques are-

1. Centrifugation
2. Evaporation
3. Sublimation
4. Chromatography
5. Distillation and Fraction Distillation

Problem 3: Define mixture.

Solution: 

Mixture are constituted by more than one kind of pure form of matter called substance. A substance cannot be separated into other kinds of matter by any physical process.

Problem 4: What are the various types of mixtures?

Solution: 

Mixtures can be classified into two types- homogeneous mixture and heterogeneous mixture. The former is a mixture which possess same properties and combination throughout their masses. while the latter possess different properties and compositions in various parts.

Problem 5: Explain the process of Centrifugation for separating cream from milk.

Solution: 

A separator is a centrifugal device that separates milk into cream and skimmed milk.  Milk is a suspension of tiny droplets of oil in a liquid. The milk is put in a closed container in big centrifuge machine. When the machine is switched on, the milk is spun at a very high speed container Due to this the milk separates into cream and skimmed milk . The cream, being lighter, floats over the skimmed milk. It can then be removed. Thus, cream is separated from milk by centrifugation.

Problem 6: Define emulsification and demulsification.

Solution: 

Emulsification is the process of mixing two immiscible liquids to form emulsion and demulsification is the process of breaking the emulsion solution. Demulsification is the process of breaking oil in an emulsion solution. It separates the oil part from the aqueous part in a mixture.