CBSE Chemistry Experiment- To Compare the Effectiveness of a Number of Emulsifying Agents in Forming Emulsions
A mixture of the dispersed phase and a dispersion medium wherein the dispersed phase remains suspended in the dispersion medium is known as a colloidal solution. In these solutions, the dispersion mediums can be water, oil, solid particles or air. Emulsions are types of colloidal solutions wherein solute and solvent are both liquids.
Examples- milk, mayonnaise, ice-creams etc. Emulsifiers are agents present in emulsions which help stabilise the emulsions. They keep both liquids in a mixed state for a prolonged period, increasing the emulsion's shelf-life. The stabilising nature of these agents is due to their chemical structure, which contains hydrophilic and hydrophobic parts.
Table of Contents
Aim
Apparatus Required
Theory
Observation
Result
Aim
To compare the effectiveness of a number of emulsifying agents in forming emulsions.
Apparatus Required
5 bottles with stoppers
Measuring cylinder
Stop-watch
5ml Pipettes
Castor oil
1% soap solution, sodium oleate solution, detergent, gelatine, and gum acacia
Distilled water
Theory
Various emulsifying agents have different effects for keeping oil in an emulsified state. Emulsifiers assist in lowering the interfacial tension present between oil and water. As a result, the oil droplets do not coagulate, so the emulsion remains stable. These agents are present at the junction of the two liquids. Since all emulsifiers have different capabilities to lower the interfacial tension, these agents have different effectiveness.
Procedure
Take 5 stoppered bottles, clean them, and label them as A, B, C, D and E.
Pour 5 ml of castor oil into all five bottles.
Measure 20 ml of distilled water with a measuring cylinder and pour it into the five bottles.
Add 5 ml of Kerosene oil, Mustard oil, machine oil, Castor oil and Coconut oil in test tubes A, B, C, D and E, respectively, one by one.
Shake the bottles vigorously for 1 minute and keep them standing.
Note the time taken for the two liquid solutions to separate.
Record your observations.
Observations
Result
The result of the above experiment states that:-
Coconut Oil takes the maximum time to separate both liquids in the presence of an emulsifier/emulsifying agent. Hence it is rated as 1.
Machine Oil takes the minimum time to separate both liquids in the presence of an emulsifier/emulsifying agent. Hence it is rated as 5.
Effectiveness of a number of emulsifying agents
Precautions
Do not perform the above experiment simultaneously for all the bottles, as noting the time of all the bottles together may not be accurate.
Pour equal drops of emulsifying agents into all the bottles.
Shake all the bottles for the same duration.
Start the stopwatch post-shaking immediately and stop the stopwatch immediately after the two layers are separated.
Lab Manual Questions
1. Why do the bottles containing the oil and water need to be shaken vigorously?
Ans: Shaking the bottles vigorously helps to mix all the contents of the bottles properly. It allows oil and water to be mixed properly with the emulsifier and helps in the formation of a stable emulsion.
2. Describe gelatin.
Ans: Gelatin is a common type of emulsifying agent. Its applications are seen in food, pharmaceutical, medical and technical fields. Gelatin is a good surfactant and hence reduces the surface tension of water to a great extent. Owing to this property of gelatin, it is considered a good emulsifying agent.
3. What are the properties of emulsion?
Ans: Emulsions are liquid-liquid colloidal solutions and hence show all the properties of colloidal solutions such as Brownian movement, Tyndall effect and Electrophoresis. When electrolytes are added to emulsions, they tend to coagulate and separate from each other.
4. What is emulsification?
Ans: The process wherein one liquid forms small droplets into another liquid. i.e. when one liquid remains suspended in another liquid, such that both of them do not mix completely with each other, is known as emulsification.
Viva Questions
1. What are the dispersed phase and dispersion medium in the above experiment?
Ans: Oil is the dispersed phase since it is present in less quantity, and water is the dispersion medium as it is present in more quantity.
2. What is meant by the emulsification of fats?
Ans: The breakdown of large fat molecules into small fat droplets easily dissolved in water is known as the emulsification of fats.
3. Name an effective emulsifying agent used.
Ans: Glycerol monostearate (GMS) and polyglycol esters are commonly used emulsifying agents.
4. What is a criterion for a good emulsifier?
Ans: A good emulsifier should be
Physically and chemically stable
Inert and compatible with other members of a product
Non-irritant and non-toxic in nature
5. What is gum acacia?
Ans: Gum acacia is a natural gum obtained from the hardened sap of tree species and is used as an emulsifier, texturing agent and stabilizer.
6. What are the side effects of emulsifiers?
Ans: When emulsifiers are consumed in excess amounts then it might lead to diarrhoea, stomach ache, vomiting feeling and bloating.
7. Define non-emulsifiers.
Ans: Non-emulsifiers are chemicals which destabilize emulsions and help in the separation of two liquids from one another.
8. What is coalescence?
Ans: When small oil droplets bump into each other and combine to form a large droplet which destabilizes, the emulsion is known as coalescence.
9. Explain the types of sols present
Ans: Sols are of two types- lyophilic which is solvent loving and lyophobic which is solvent repelling.
10. Give examples of emulsifiers.
Ans: Diacetyl tartaric acid ester of monoglyceride, and sodium stearoyl lactylate, sodium phosphates are a few examples of emulsifiers.
Practical Based Questions (MCQs)
Emulsions are of two types, ______and _____
Oil in water, water in oil
Oil in oil, water in water.
Water and air
Water in air and air in water
Ans: Oil in water, water in oil
Emulsifying agents are
Have affinity towards Hydrophobic compounds
Have affinity towards Hydrophilic compounds
Both A and B
None of the above
Ans: Both A and B
Which one is not an emulsifying agent?
Salt
Gelatin
Soap
Lecithin
Ans: Salt
Whisking and blending action help in______
Bring oil droplets nearby
Dispersing the oil in the liquid
Make the emulsion coagulate
All of the above
Ans: Dispersing the oil in the liquid
The best natural emulsifier is
Beeswax
Sodium phosphates
Mono and diglycerides
Both A and B
Ans: Beeswax
Find the odd man out
Gelatin
Sodium ions
Soaps
Gums
Ans: Sodium ions
______is the rising up of the colloidal particles due to buoyancy or due to_____force which breaks an _____.
Flocculation, centrifugal, colloidal solution
Creaming, centripetal, true solution
Creaming, centripetal, emulsion
Flocculation, the centrifugal, true solution
Ans: Creaming, centripetal, emulsion
Find the true statement.
Colloidal solutions are true solutions
A homogeneous solution shows the Tyndall effect
Hydrophilic sols are water-loving sols
Lyophobic sols are only water-repelling sols
Ans: Hydrophilic sols are water-loving sols
An emulsion contains_____, _____and _____
Oil, water, emulsifier
Water, alcohol, sol
Water, salt, emulsifier
Water, sugar, sol
Ans: Oil, water, emulsifier
Which of the following gives oil in water type of emulsion?
Protein
Milk
KCl in water
Both A and B
Ans: Both A and B
Conclusion
From the above experiment, we can conclude that emulsifiers are chemical components which keep the oil-water emulsion in an emulsified state for a long duration. This property of these agents is because emulsifiers have both hydrophobic and hydrophilic tails, which helps them to stabilize emulsions and prevent flocculation and coalescence in the emulsion. The best emulsifying agent from the above is ______ and keeps the solution stable for ______time period. Common examples of emulsifiers are lecithin, soy lecithin, mustard, etc.
FAQs on To Compare the Effectiveness of a Number of Emulsifying Agents in Forming Emulsions
1. What is the main objective of the CBSE Class 12 experiment on comparing the effectiveness of emulsifying agents?
The primary objective is to determine and compare the stabilising power of different emulsifying agents (like soap, detergent, and gum) in an oil-in-water emulsion. This is done by measuring the time it takes for the oil and water layers to separate after being mixed with each agent. A longer separation time indicates a more effective emulsifier.
2. What is the fundamental role of an emulsifying agent in this experiment, and how does it work?
An emulsifying agent acts as a stabiliser for the emulsion. It works by reducing the interfacial tension between the two immiscible liquids (oil and water). The agent's molecules have a hydrophilic (water-attracting) head and a hydrophobic (oil-attracting) tail, allowing them to form a protective layer around the oil droplets and prevent them from coalescing.
3. For the board practical exam, what are the key observations you need to record to determine the effectiveness of an emulsifier?
The most important observation to record is the time taken for the two immiscible layers to separate completely after vigorous shaking. To compare effectiveness, you should record this time for each emulsifying agent tested and then arrange them in decreasing order of time taken. The agent that results in the longest stability time is considered the most effective.
4. Why is a detergent generally a more effective emulsifying agent than soap, especially when using hard water?
This is a frequently asked viva question. Soaps are sodium or potassium salts of long-chain fatty acids. In hard water, they react with calcium and magnesium ions to form an insoluble precipitate, or 'scum', which reduces their cleaning and emulsifying ability. Detergents, which are typically salts of long-chain alkyl hydrogen sulphates or sulphonic acids, do not form insoluble precipitates with these ions and thus remain effective emulsifiers.
5. Why is vigorous shaking a critical step in this experiment? What could happen if the shaking is insufficient?
Vigorous shaking is essential because it provides the mechanical energy needed to break down the larger oil mass into very small droplets, significantly increasing the surface area for the emulsifier to act upon. If the shaking is insufficient, a proper dispersion will not form, and the emulsion will be highly unstable, separating almost immediately. This would lead to inaccurate and unreliable results for comparing emulsifier effectiveness.
6. How can you experimentally determine if an emulsion is of the oil-in-water (O/W) or water-in-oil (W/O) type?
Two common tests can be performed:
- Conductivity Test: An oil-in-water (O/W) emulsion will conduct electricity as water (the continuous phase) is a good conductor. A water-in-oil (W/O) emulsion will not, as oil (the continuous phase) is a non-conductor.
- Dye Test: Add a drop of a water-soluble dye (like methylene blue). If the background becomes coloured, it is an O/W emulsion. If only the dispersed droplets get coloured, it is a W/O emulsion.
7. What are some important criteria for selecting a good emulsifier for a specific purpose?
A good emulsifier should ideally be:
- Physically and chemically stable.
- Inert and compatible with the other ingredients in the mixture.
- Non-toxic and non-irritant, especially for food and cosmetic applications.
- Effective in small concentrations.
- Able to produce and maintain the desired viscosity.
8. What crucial precautions must be taken while performing this experiment to ensure your results are accurate and comparable?
To ensure a fair comparison and accurate results, you must:
- Use the exact same volume of oil and water in every test bottle.
- Add an identical amount of each emulsifying agent being tested.
- Shake all bottles for the same duration and with consistent intensity.
- Start the stopwatch immediately after shaking ceases and stop it as soon as the layers separate.
- Test each emulsifier one by one to avoid errors in observing the separation time.
9. What do the terms 'coalescence' and 'creaming' mean in the context of emulsion stability?
Both terms describe processes that lead to emulsion breakdown. Creaming is the process where dispersed droplets move under gravity to form a concentrated layer at the top or bottom, but they remain as individual droplets. Coalescence is an irreversible process where these droplets merge to form larger droplets, eventually leading to the complete separation of the two phases.
10. Beyond the chemistry lab, provide two real-world examples where emulsifiers are essential.
Emulsifiers are crucial in many industries. For example:
- Food Industry: In mayonnaise, lecithin from egg yolk acts as an emulsifier to keep oil and vinegar mixed. In ice cream, emulsifiers prevent ice crystal formation and create a smooth texture.
- Cosmetics and Pharmaceuticals: Emulsifiers are used to make stable creams and lotions by mixing oil and water-based ingredients, ensuring a consistent product.
