With reference to 'Colloidal Solutions', consider the following statements: 1. They appear homogeneous but are actually heterogeneous. 2. Their particles are large enough to be seen with the naked eye. 3. They scatter a beam of visible light. Which of the statements given above is/are correct?

The correct option is (c). Explanation Colloidal Solutions represent a state of matter intermediate between true solutions and suspensions. They are mixtures where microscopically dispersed insoluble particles of one substance are suspended throughout another substance. - Statement 1 is Correct: Colloidal solutions appear to be homogeneous to the naked eye (e.g., milk, fog) because the particles are uniformly distributed. However, they are physically heterogeneous mixtures consisting of two phases: the dispersed phase (solute-like) and the dispersion medium (solvent-like). - Statement 2 is Incorrect: The particles in a colloidal solution have a diameter range of 1 to 1000 nanometers (nm). While they are larger than the particles in a true solution, they are still too small to be seen with the naked eye. They can typically be observed only with the help of an ultramicroscope. - Statement 3 is Correct: Colloidal particles are large enough to scatter a beam of visible light passing through them. This scattering renders the path of the light beam visible, a phenomenon known as the Tyndall effect. This property distinguishes colloids from true solutions, where particles are too small to scatter light. Key Takeaway: Colloids are heterogeneous mixtures with particle sizes (1–1000 nm) intermediate between true solutions and suspensions, uniquely characterized by their ability to scatter visible light (Tyndall effect).

NCERT Class 9 Science — Chapter 2: Is matter around us pure?

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With reference to 'Colloidal Solutions', consider the following statements:

They appear homogeneous but are actually heterogeneous.
Their particles are large enough to be seen with the naked eye.
They scatter a beam of visible light.

Which of the statements given above is/are correct?

Official previous-year question

Verified 1 Aug 2026.

Options

A1 and 2 only
B2 only
C1 and 3 only
D1, 2 and 3

Did you get this right?

Solution

The correct option is (c).

Explanation

Colloidal Solutions represent a state of matter intermediate between true solutions and suspensions. They are mixtures where microscopically dispersed insoluble particles of one substance are suspended throughout another substance.

Statement 1 is Correct: Colloidal solutions appear to be homogeneous to the naked eye (e.g., milk, fog) because the particles are uniformly distributed. However, they are physically heterogeneous mixtures consisting of two phases: the dispersed phase (solute-like) and the dispersion medium (solvent-like).
Statement 2 is Incorrect: The particles in a colloidal solution have a diameter range of 1 to 1000 nanometers (nm). While they are larger than the particles in a true solution, they are still too small to be seen with the naked eye. They can typically be observed only with the help of an ultramicroscope.
Statement 3 is Correct: Colloidal particles are large enough to scatter a beam of visible light passing through them. This scattering renders the path of the light beam visible, a phenomenon known as the Tyndall effect. This property distinguishes colloids from true solutions, where particles are too small to scatter light.

Key Takeaway: Colloids are heterogeneous mixtures with particle sizes (1–1000 nm) intermediate between true solutions and suspensions, uniquely characterized by their ability to scatter visible light (Tyndall effect).

Your note

More from Chapter 2: Is matter around us pure?

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The correct option is (c).

Explanation

Statement 1 is Correct: Colloidal solutions appear to be homogeneous to the naked eye (e.g., milk, fog) because the particles are uniformly distributed. However, they are physically heterogeneous mixtures consisting of two phases: the dispersed phase (solute-like) and the dispersion medium (solvent-like).
Statement 2 is Incorrect: The particles in a colloidal solution have a diameter range of 1 to 1000 nanometers (nm). While they are larger than the particles in a true solution, they are still too small to be seen with the naked eye. They can typically be observed only with the help of an ultramicroscope.
Statement 3 is Correct: Colloidal particles are large enough to scatter a beam of visible light passing through them. This scattering renders the path of the light beam visible, a phenomenon known as the Tyndall effect. This property distinguishes colloids from true solutions, where particles are too small to scatter light.