chemical suspension



We explain what a suspension is in chemistry, its phases and main characteristics. Also, its properties and experiments.

Fruit juices are suspensions, so they must be shaken before serving.

What is a chemical suspension?

In chemistry, suspension is understood to be a type of heterogeneous mixture made up of small particles of a solid scattered in the middle liquid in which they cannot be dissolved. The name "suspension" comes from the fact that the particles are suspended. That is, the solid does not dissolve in the liquid, even if it is microscopic solid particles.

All suspensions, then, are made up of:

  • Dispersed phase. It is the solid phase. It consists of fine solid particles that are insoluble in the liquid or dispersing phase.
  • Dispersing phase. It is the liquid phase (also called continuous or external). It consists of a watery or greasy liquid.

In addition, they usually contain surfactants, which are dispersing agents, whose role is to prevent solids from agglutinating or sedimenting; and even stabilizing substances, which keep the suspension in balance. These last two elements are essential in the industrial production of suspensions.

Suspensions are very useful in various industries, and are the fundamental principle of the aerosol. A fruit juice is an example of a suspension, since the solid pulp is suspended in the Waterbut if given enough time, decant by action of the gravity towards the bottom of the container. But if we shake it, it recovers its properties temporarily.

Properties of a suspension

The suspensions are, for the most part, not very stable. This is because the solid particles can be distributed homogeneously in the continuous phase without agglutinating or sedimenting only for a certain time.

The stability period depends essentially on the viscosity the continuous phase (the higher the viscosity, the longer the time), the size of the dispersed particles and the temperature to which the compound. In addition, stabilizing or anti-caking additives are usually used to maximize the stability period.

On the other hand, suspensions may seem inseparable, but given enough time it is possible. decant both phases and allow the solids to settle. Also, they can be completely separated just by methods specific to filtration or centrifugation.

Another interesting property of suspensions is that they can act as solids under certain circumstances and as liquids in others. Thus, they can flow like liquids, but offer a certain toughness to impacts like solids do.

Emulsion and suspension

An emulsion is also a heterogeneous mixture, but its two phases are liquid.

Emulsions and suspensions are somewhat similar. The former are also about heterogeneous mixtures of phases that do not interpenetrate 100%, but which in this case are both liquid, that is, an emulsion is a heterogeneous mixture of immiscible liquids.

These two liquids are temporarily indiscernible from each other, but given enough time, they will separate just like suspensions. Of course: unlike emulsions, suspensions do not have a color specific determined.

Suspension experiments

The flour and water form a suspension of a particular consistency.

Next, we will explain a couple of experiments homemade to demonstrate the properties of suspensions:

  • Corn flour suspension
    • You will need to. 1 cup of flour or cornstarch, 1 bowl, about ½ cup of water, a spoon, a pie plate.
    • Instructions. Pour the flour or cornstarch into the large bowl, adding the water slowly while stirring with the spoon. Don't add all the water if you don't have to. Once you get a watery consistency, hold the mixture in your hands and watch it spill. Then hit the suspension with one hand and see how it resists, like a solid.Pour unmixed water into the standing plate and try to repeat the sensations: hold it and hit it. Record the differences between the liquid and the suspension.
  • Talc suspension
    • You will need to. 2 tablespoons of talcum powder, a glass of water, a spoon.
    • Instructions. Pour the talc into the glass of water gradually, while stirring with the spoon, until you get a uniform mixture. Take note, if any, of the solid remains at the bottom of the glass. Place the glass in a place where no one will touch it and it is at rest. Come back in 5 minutes. Take note, if any, of the solid remains on the bottom of the glass. Repeat the procedure at 10, 15, 20 and 30 minutes, to observe how the suspended solids settle to the bottom, separating the two phases.
!-- GDPR -->