Colloids

Fog is a solution of liquid in gas. In chemistry, a solution is a homogeneous mixture of two or more substances. When identifying the constituents of a solution, the terms solute and solvent are used. In this context, fog is formed when tiny droplets of a liquid (usually water) are dispersed in a surrounding gas (air). This type of solution is commonly referred to as an aerosol.

In the given options:

• Liquid in gas - This accurately describes fog, as it consists of liquid water droplets suspended in air.
• Gas in liquid - This would refer to a different type of solution, such as soda water (carbon dioxide in water).
• Solid in gas - This describes smoke or another form of particulate matter in air.
• Gas in gas - This refers to a homogeneous mixture of gases, like the air itself.

Therefore, the correct answer is Liquid in gas.

In a colloidal solution, the dispersed phase is the phase that is distributed uniformly throughout another substance. This uniformly distributed substance is typically present in a smaller amount and is often referred to as the 'solute'. Therefore, in colloidal solutions, the correct term for the dispersed phase is Solute.

Colloidal solutions consist of two main parts:

• Dispersed Phase: The solute-like component, which is distributed as particles.
• Dispersion Medium: The solvent-like component, which disperses the particles.

Among the given options:

• Solute: Correct, as the dispersed phase in a colloidal solution.
• Solution: Incorrect, it is the combination of the dispersed phase and the dispersion medium.
• Suspension: Incorrect, refers to a different type of mixture where the dispersed particles are larger and visible.
• Mixture: Incorrect, a broad term that could refer to any combination of substances, not specific to colloids.

Blood is classified as a colloidal solution. To understand why, let's analyze the characteristics of blood and compare them to different types of solutions.

• True solution: In true solutions, the solute particles are ions or small molecules that are completely dissolved and distributed uniformly within the solvent. The particles in true solutions are usually less than 1 nanometer in diameter and cannot be seen under a microscope. Blood, however, contains cells and proteins that are much larger and are visible under a microscope, placing it outside the realm of true solutions.
• Saturated solution: A saturated solution occurs when a solvent cannot dissolve any more solute at a given temperature and pressure. Blood does not fit this description as it isn't a simple solute-solvent mixture but rather a complex medium with cellular elements.
• Suspension: In suspensions, the particles are larger than 1 micrometer and can be separated by filtration. These particles eventually settle out. In blood, the particles do not settle out in the same way as they are stabilized by surrounding plasma, indicating that blood is not a suspension.
• Colloidal solution: In colloids, the particles range from 1 nanometer to 1 micrometer, remaining evenly distributed throughout the solution. Blood consists of plasma proteins, such as albumin, which form a colloidal structure. The colloidal particles in blood include these proteins, as well as other larger components such as cells that remain suspended and do not settle out, meeting the criteria of a colloidal solution.

Therefore, the correct answer is that blood is a colloidal solution.

Milk is best described as a colloidal solution. This classification arises from its composition and properties:

• A colloid is a mixture where one substance of microscopically dispersed insoluble particles is suspended throughout another substance.
• In milk, fine particles of fat and protein are dispersed in water, rendering it a colloidal system.
• Unlike true solutions, the particles in colloids are larger and do not settle out upon standing, nor are they easily filtered.
• Colloids exhibit the Tyndall effect, which is the scattering of light, another characteristic feature observed in milk.

Therefore, based on these observations and properties, milk is classified as a colloidal solution.

To determine the characteristic particle size range for colloidal solutions, we need to understand the nature of colloids in chemistry. A colloidal solution, which is a type of heterogeneous mixture, consists of particles that are dispersed throughout the solution but do not settle out due to gravity like those in suspensions.

The key factor distinguishing colloids from other types of mixtures, such as solutions and suspensions, is the size of its dispersed particles:

• True solutions: Particle size < 1 Å
• Colloidal solutions: Particle size between 10 Å and 2000 Å
• Suspensions: Particle size > 2000 Å

This information helps us identify the correct option for the particle size range of colloidal solutions from the given options:

• 1 Å – 10 Å (True solution)
• 10 Å – 2000 Å (Correct for colloids)
• More than 2000 Å (Suspension)
• Less than 1 Å (True solution)

Therefore, the particle size in a colloidal solution is 10 Å – 2000 Å.

The Tyndall effect is a phenomenon where light is scattered by particles in a colloid or in small particles in a fine suspension. This occurs when the diameter of the particles is in the range of 1 nanometer to 1 micrometer. The effect is named after the 19th-century physicist John Tyndall who first studied it.

Let's explore why the correct answer is "Scattering of light":

• Scattering of light: The Tyndall effect is directly related to the scattering of light. When a beam of light passes through a colloidal solution or a suspension, the particles scatter the light in different directions, making the path of the beam visible. This is the correct explanation for the phenomenon observed in the Tyndall effect.
• True solutions of light: In a true solution, the solute particles are molecular-sized (less than 1 nanometer) and do not scatter light; thus, they do not show the Tyndall effect.
• Refraction of light: Refraction refers to the bending of light as it passes from one medium to another, which is a different phenomenon from scattering.
• Movement of particles: While the movement of particles can cause scattering, the Tyndall effect specifically refers to the scattering aspect rather than the mere movement of particles.

Therefore, the Tyndall effect is characterized by the scattering of light due to the presence of particles in a colloid or a fine suspension.

The Tyndall effect is a phenomenon observed when a beam of light is scattered by particles in a medium. It is typically exhibited by colloidal solutions. Let's examine why this is the case in comparison with other systems mentioned:

1. True Solutions: True solutions have solute particles, which are molecularly dispersed and far too small (less than 1 nm) to scatter light. Therefore, true solutions do not exhibit the Tyndall effect.

2. Suspensions: While suspensions have larger particles that can scatter light, these particles are heavy enough to eventually settle out due to gravity, thus suspensions are not stable and inconsistent in exhibiting the Tyndall effect.

3. Colloidal Solutions: Colloids contain particles of intermediate size (1-1000 nm) that are large enough to scatter light, but small enough to remain suspended in the medium without settling. This stability and particle size make colloidal solutions ideal for displaying the Tyndall effect, where the path of a light beam can be visibly observed due to scattered light.

4. Crystals: Crystals have a solid, ordered structure and do not allow for the scattering of light in the manner a liquid or gas medium does, hence they do not exhibit the Tyndall effect.

In conclusion, the correct answer is: Colloidal solutions.