An Introduction
Take a glass of water and add a tablespoon of flour to it. Now stir it well. What do you see? Does the water and flour mixture appear clear or turbid (unclear)? Yes, you are right. The mixture appears turbid. What do you think, what have you prepared? A solution, a colloid or a suspension? Well if you observe this mixture for some more time then you will see that particles of flour slowly settle down at the bottom of the glass. This indicates that it is a suspension. We will discuss suspensions in detail from a chemistry point of view. With this, we will discuss solutions, colloids, and solubility as well in comparison with suspensions. So that it will help you to distinguish mixtures as suspension, solution, or colloids.
What is Suspension?
A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. In other words, suspensions are non – homogeneous systems in which solids are dispersed in liquids. Constituent particles of a suspension are large enough that gravity can pull them down out of the dispersion medium. These particles can be easily separated by the filtration method from the dispersion medium. The size of particles in suspension is at least 100 times larger than particles of solution.
Examples of Suspension
Some common examples of suspension are listed below –
Mixture of flour and water
Mixture of chalk and water
Muddy water
Mixture of sand and water
Paints (water-based)
Mixture of Slaked lime (Calcium hydroxide) in water
Mixture of magnesium hydroxide and water (Milk of Magnesia)
Lemonade
Some salad dressings such as thousand island, honey mustard dressing
Sattu sharbat
Properties of Suspension
General characteristics and properties of suspensions are listed below –
It is a heterogeneous mixture.
Constituent particles of the suspension mixture can be seen by naked eyes.
The size of particles in suspension is more than 100 nm.
Suspension shows the Tyndall effect. It means particles of a suspension scatter a beam of light passing through it and making its path visible.
If the suspension is left undisturbed, its particles settle down. It shows that suspension is an unstable mixture. In this condition, the suspension does not show the Tyndall effect.
Constituent particles of a suspension can be separated by filtration.
What is a Solution?
A solution is a homogeneous mixture of two or more substances. A solution has a solute and solvent as its components. The component of the solution which dissolves the other component in it is called solvent while the other component which gets dissolved in the solvent is called the solute. Generally, in a solution solute is present in a lesser amount than solvent.
Examples of Solutions
You can see many examples of solutions in your daily life. A few examples of solutions are listed below –
Mixture of sugar and water.
Tincture of iodine (solution of iodine in alcohol)
Soda water
Air (a homogeneous solution of various gasses)
Alloys (Mixture of two or more metals or a metal and a non – metal which cannot be separated by physical methods. For example – Brass, Stainless steel etc.)
Properties of Solution
Solution shows the following properties –
It is a homogeneous mixture.
The size of the particles in the solution is less than 1 nm in diameter.
Particles of the solution cannot be seen by naked eyes.
Particles of solution cannot be separated by simple physical methods of separation such as filtration.
Some common examples of colloids are listed below in tabular form with their dispersion phase, dispersion medium and type –
Examples of Colloids
Properties of a Colloid
Properties of Colloids are listed below –
A colloid is a heterogeneous mixture.
Particles of colloids are not visible by naked eyes.
In colloids, dispersed phase particles have a diameter between 1 – 100 nm (approximately).
They show the Tyndall effect.
In colloids, dispersed particles do not settle down when left undisturbed.
Colloids are stable mixtures.
In colloids, the dispersed phase and dispersion medium cannot be separated by filtration.
In colloids, dispersed particles show Brownian movement.
Comparison between properties of suspension, colloids and solution is given below in tabular form for your better conceptual clarity –
Difference between Suspension, Colloids and Solution
FAQs on Suspensions
1. What is a Concentrated Solution?
The proportion of the solute and solvent can be varied. Depending upon the amount of solute present in a solution, it can be called a dilute, concentrated or saturated solution.
Dilute and concentrated are comparative terms. A solute that contains a relatively larger amount of solute is called a concentrated solution while a solute that contains a relatively smaller amount of solute is called a dilute solution. On the other hand, at any particular temperature, a solution that has dissolved as much solute as it is capable of dissolving is called a saturated solution.
2. What is Solubility?
The amount of solute present in the saturated solution at a particular temperature is called the solubility of that saturated solution. Thus, solubility is the ability of the solute to get dissolved in a solvent at a particular temperature.
According to the IUPAC definition, solubility is the analytical composition of a saturated solution expressed as a proportion of a designated solute in a designated solvent.
Solubility can be expressed in various units of concentration such as molarity, molality, mole fraction, mole ratio etc.
3. What is a Colloid?
A heterogeneous mixture in which particles are uniformly spread throughout the solution is called a colloid. It is also called a colloidal solution. The term colloid is sometimes used particularly for dispersed substances alone in the colloidal solution, but the term colloidal suspension refers unambiguously to the overall mixture. Although suspension and colloidal suspension (solution) both are different types of mixtures. It appears to be homogeneous because of its smaller particle size than suspension. It also shows the Tyndall effect.
4. How are colloids prepared by using the Condensation Method?
To prepare colloids with the condensation method, small solute particles are condensed to form a disassembled phase particle. Some of the methods are-
Oxidation- By passing oxygen gas through the solution of hydrogen sulphides, colloidal sulphur can be obtained. Oxidizing agents like HNO3, H3Br2 can be used to perform this reaction.
2H₂S + O₂ → 2H₂O + 2S (which is Sulphur sol)
Double Decomposition- Double Decomposition is used to obtain a sol of arsenic sulphide In Double Decomposition, the hydrogen sulphide is passed via an Arsenious oxide cold solution in water.
As₂O₃+ 3H₂S → As₂ S₃+ 3H₂O Arsenic sulphide (sol)
Double Decomposition- A solution of arsenic sulphide can be acquired in Double Decomposition of the given elements. Hydrogen sulphide is passed through a cold Arsenious oxide solution in water.
As₂O₃ + 3H₂S → As₂S₃ + 3H₂O Arsenic sulphide (sol)
Reduction- Several metals like gold, silver, etc are obtained in a colloidal form by reacting the aqueous solution of these metal salts with appropriate reducing agents like phenylhydrazine, formaldehyde, hydrogen peroxide, etc. The gold sol made in the reduction of gold chloride solution has a purple colour. That's the reason it is also called the purple of Cassius.
2AuCl₃+ 3SnCl₂ → 3SnCl₄+ 2Au(gold sol)
2AuCl₃ + 3HCHO + 3H₂O → 2Au + 3HCOOH + 6HCl
Hydrolysis- Several salt solutions are quickly hydrolysed by boiling a dilute solution of their corresponding salts. For Example- ferric hydroxide and aluminum hydroxide sols are acquired by boiling solutions of the corresponding chloride. Silicic acid sol is acquired through this similar method, by hydrolysis by sodium silicate.
Change of Physical State- Sols of substances like mercury is made by passing the vapour via cold water holding a suitable stabilizer such as ammonium salt or citrate.
Exchange of Solvent- In the process of Exchange of Solvent, colloidal sol of the given substances like sulphur, etc which are soluble in alcohol but not soluble in water can be made by flowing their alcoholic solution into water.
Excessive Cooling- Excessive Cooling is used in obtaining colloidal sol of ice. Ice is poured in an organic solvent like chloroform ether and Sol of ice is acquired by freezing the solution of water in the solvent. At this moment, the molecules of water are not in the solution individually to assemble the particles of colloidal size.
5. Explain Aerosols with an Example?
In earth's natural air or any given gas, a colloid of small solid particles or liquid droplets is known as an aerosol. Natural and man-made aerosols can be found in the air and the environment. For Example- Smoke is produced up of small solid and liquid particles as well as gasses that escape from burning things like candles, and internal engine parts. Smoke causes air pollution, which is created by humans. Many of the elements in fire smoke are extremely hazardous and can cause death in the worst cases.