To Prepare a Colloidal Solution of Gum

Colloidal solutions are heterogeneous solutions wherein the solute particles remain dispersed in the solvent medium. The solutes in colloidal solutions are called the dispersed phase, and the solvent is known as the dispersion medium. Depending on the affinity of the dispersed phase with the dispersion medium, colloids can be lyophilic- showing high affinity towards the solvent, or can be lyophobic- showing low affinity towards the solvent. Colloidal solution examples include starch, gums, egg albumin, etc.

Table of Contents

• Aim 

• Apparatus Required

• Theory

• Procedure

• Observations

• Results

Aim 

To prepare a colloidal solution of gum.

Apparatus Required

1. Beakers

2. Glass rod

3. Funnel

4. Filter-paper

5. Mortar and pestle 

6. Burner

7. Soluble gum

8. Distilled water

Theory

1. Lyophilic sols are solutions where the solute particles have more affinity towards the solvent and hence are more stable than lyophobic sols. 

2. In lyophilic sols, the stability is due to the ability of colloidal particles to get dissolved in the solvent/ dispersion medium. 

3. Charges on various colloidal particles help them to remain suspended in the solution and prevent coagulation. 

4. The preparation of colloids, such as gum, starch etc., is accelerated if the water is hot or boiling.

Procedure

1. Take 500 mg of gum in a mortar and pestle and add a few ml of warm distilled water.

2. Grind the gum particles and make a paste of it.

3. Transfer this paste into a 50ml beaker.

4. In a 250 ml beaker, take 100 ml of distilled water and place it over a Bunsen burner.

5. Heat the water until it is warm.

6.  Pour the gum paste into the 250ml beaker while constantly stirring.

7. Keep it in the hot water solution for a while and then allow it to cool.

8. Filter the beaker's contents through the filter paper using a funnel.

9. Note the observation and write the results.

Observations

A yellowish-coloured colloidal solution is obtained, containing particles of gum. The dispersion medium here is water, the dispersed phase is gum particles.

Result

A yellowish-coloured colloidal solution is prepared. The gum particles show a very high affinity towards the dispersion medium; hence, it is known as a lyophilic colloidal sol. It is quite stable.

Preparation of colloidal solution of gum

Precautions

1. Clean all apparatus.

2. Distilled water has to be used and not tap water.

3. Stir the ingredients while pouring the paste into hot water.

4. Be careful while working close to the burner.

5. Devise precautions while pouring the paste into hot water.

6. Filter the gum sol carefully.

Lab Manual Questions

1. Why do particles of the dispersed phase remain suspended in the dispersed mediums?

The dispersed phase particles are either very large molecules or are made from aggregates of small molecules; hence, dispersed phase particles remain suspended in the dispersed mediums of colloidal solutions.

2. What are colloidal solutions?

Colloidal solutions are heterogeneous systems in which the solute and solvent are immiscible within each other, and hence the solute remains suspended with the solvent medium. Examples of colloids are gum sol, starch sol, and emulsifiers such as milk, butter etc. 

3. What is gum?

Gums are exudates obtained from barks and various trees or shrubs. They are obtained by cutting the bark of the plants and collected every season. Gums are mostly used as adhesive material.

4. Why do we have to pour the gum paste slowly in the above experiment?

If the gum paste is poured quickly in water, it may form lumps or precipitation of the gum particles. Therefore, the prepared gum paste must be slowly poured inside the beaker containing water accompanied by constant stirring.

Viva questions 

1. What is the approximate range of size of the dispersed phase particles?

Ans: The dispersed phase particle size ranges from 10-9 to 10-6 m.

2. If water is the dispersion medium, which terms are used for solvent loving and repelling?

Ans: If water is the dispersion medium, it is known as hydrophilic and hydrophobic.

3. Give examples of lyophilic sols.

Ans: Lyophilic sols are Egg albumin, starch, gums, gelatin, rubber etc. 

4. What are lyophobic sols?

Ans: Lyophobic sols are solvent-repelling particles which do not have high affinity towards the dispersion medium and are very unstable. They coagulate very easily upon the addition of any electrolyte.

5. Why is gum solution prepared in warm water?

Ans: Gum gets easily dissolved in water, hence boiling water is not required, and warm water can be used.

6. Give examples of lyophobic sols.

Ans: Examples of lyophobic sols are metal sulphides, metal hydroxides, etc.

7. What is coagulation?

Ans: Coagulation is known as the process of accumulating all the colloidal particles or small aggregations of colloidal particles to settle down and form a precipitate.

8. What is peptisation?

Ans: The process through which the settled precipitate is brought back into a colloidal solution using an appropriate peptising agent is known as peptisation.

9. What are blood anticoagulants?

Ans: Anticoagulants are known as blood thinners and are chemical substances that prevent blood clots forming in our body.

10. What is hydrophilic sol?

Ans: A hydrophilic sol is a colloidal solution in which the dispersed phase has a high affinity towards water (dispersion medium).

Practical Based Questions (MCQs)

1. Is gum lyophilic or lyophobic?

1. Lyophilic

2. Lyophobic

3. Both 

4. None of the above

Ans: Lyophilic

2.  A type of colloidal solution where the dispersion medium and dispersed phase are liquid is known as____

1. Sol

2. Aerosol

3. Emulsion

4. Both A and C

Ans: Emulsion

3. What is the foam type of colloidal solution?

1. Gas dispersed phase in solid/liquid dispersion medium

2. Liquid dispersed phase in solid/liquid dispersion medium

3. Gas dispersion medium in solid/liquid dispersed phase

4. All of the above

Ans: Gas dispersed phase in solid/liquid dispersion medium

4. Colloidal sols which contain water-repelling solutes are known as____

1. Hydrophobic sols

2. Hydrophilic sols

3. Emulsified sols

4. Liquid sols

Ans: Hydrophobic sols

5. Find the odd man out.

1. Starch

2. Gum

3. Ferric hydroxide

4. Gelatin

Ans: Ferric hydroxide

6. Negatively charged sols are______and _____

1. Starch, Arsenious sulphide

2. Starch only, Arsenious sulphide

3. Hydrated Ferric oxide, water

4. Ferric oxide, NaOH

Ans: Starch, Arsenious sulphide

7. Which of the following is true-

1. Hydrophilic sol contains alcohol as a dispersion medium

2. Lyophobic sols are water-loving

3. Cloud is an aerosol type of colloid

4. Whipped cream is a type of sol

Ans: Cloud is an aerosol type of colloid

8. Find the odd man out

1. Shaving cream

2. Milk

3. Butter

4. Mayonnaise

Ans: Shaving cream

9. Why is smoke called a colloid?

1. Because solid particles are suspended in a gas

2. Because liquid, particles are suspended in water

3. Because oils are suspended in a gas

4. Because of gas, particles are suspended in a solid

Ans: Because solid particles are suspended in a gas

10.  Which of the following is not a method of preparation of colloids?

1. Chemical methods

2. Electrical disintegration

3. Peptization

4. Coagulation

Ans: Coagulation

Conclusion

From the above experiment, we can conclude that colloidal solutions are solutions which have suspended solute particles present inside the solution. Here, the solutes and solvents do not mix completely and form a single phase. Gum, Starch, Gelatin, and rubber are common examples of lyophilic sols. Sols are a type of colloidal solution in which the dispersion medium is liquid, and the dispersed phase is solid. Lyophilic sols are solvent-loving, showing a strong affinity towards the solvent they are dispersed into.