Colloidal Solution

• Colloids: A colloid is a type of mixture where tiny particles of one substance are dispersed evenly throughout another substance. These particles are small but still larger than molecules or simple ions.
• Dispersed Phase: The phase that is dispersed or present in the colloidal particle shape is called the dispersed phase. 
• Dispersion medium: Dispersion medium is the continuous phase of a colloid. It is the phase in which the dispersed phase is distributed.

The particles of a colloid are uniformly spread throughout the solution. Due to the relatively smaller size of particles, the mixture appears to be homogeneous. But actually, a colloidal solution is a heterogeneous mixture, for example, milk.

• Appearance: Colloids are translucent, meaning they partially allow light to pass through while scattering some of it. This scattered light makes a beam visible, like sunlight shining through fog.
• Separation: Colloids cannot be separated by regular filter paper because the particles are very small and pass through the pores of the filter.

Types of Colloids:

1. Solid in Gas: An example is smoke, where solid particles are mixed in air.
2. Liquid in Gas: An example is fog or clouds, where tiny liquid droplets are suspended in the air.

Properties of Colloids:

• A colloid is a heterogeneous mixture. The size of particles in a colloid is too small to be individually seen by naked eyes.
• Colloids are big enough to scatter a beam of light passing through them and make their path visible.
• They do not settle down when left undisturbed; that is, a colloid is quite stable.
• They cannot be separated from the mixture by the process of filtration. But it can be separated through centrifugation.

The components of a colloidal solution are the dispersed phase (solute-like) and the dispersion medium (solvent-like)

Common examples of colloids,

Matter can be made up of elements, which are the simplest forms of substances. An element is a pure substance consisting of only one kind of atom. For example, oxygen is an element.

1. Aim: To observe the difference between a simple mixture and a compound formed by heating iron filings and sulphur using a horseshoe magnet.

2. Requirements: 7 g of iron filings, 4 g of sulphur, two evaporating dishes, a glass rod, a horseshoe magnet, and a heat source.

3. Procedure

• Place iron filings in one dish and sulphur in another.
• Bring a magnet near both to observe their properties.
• Mix the iron filings and sulphur, stir, and test with the magnet to check for magnetic properties.
• Heat the mixture, let it cool, and observe any colour change. Test the cooled substance with the magnet to note any differences.

4. Conclusion

• Before Heating: Iron and sulphur formed a physical mixture, keeping their individual properties.
• After Heating: A chemical reaction occurred, forming iron sulphide, a new compound with different properties. The magnet no longer attracted the substance, indicating a chemical change.