Which of the following is homogeneous? A. Milk B. Paint C. Shampoo D. None of these
Hint: Mixtures can be either homogeneous or heterogeneous. A homogeneous mixture is something which has the same proportions of its components throughout solid, liquid or gaseous mixtures.
Complete answer: Mixtures are of two types; homogeneous and heterogeneous. Heterogeneous mixtures in turn are of mainly two types, colloids and suspensions. The difference lies in the particle sizes of the substances. We will discuss this question by looking at the options given: A. Milk: Milk is thought to be a homogeneous mixture. But actually it is an example of colloidal solution. Milk has butterfat globules dispersed within a water-based solution. The dispersed medium (the solvent) and dispersed phase (the solute) both are liquids. The mixture of liquids is called emulsion. B. Paint: Paint is also a type of colloidal solution. It is a ‘sol’ in which the dispersed medium (the solvent) is liquid and the dispersed phase (the solute) is solid. So, it is a heterogeneous mixture. C. Shampoo: Two types of conditioning are given by shampoos, one wet hair conditioning and other is dry hair conditioning. A colloid structure of coacervate (combined by opposite charges) formed by cationic polymer and anionic surfactant in water is responsible for wet hair conditioning. Dry hair conditioning is done as a result of depositing silicones and conditioning oils on hairs. Thus, shampoo also comes under heterogeneous mixtures only. The correct answer of this question is none of these as all other options come under heterogeneous mixture, So, the correct answer is “Option D”.
Additional Information: The differences between homogeneous and heterogeneous mixture are:
Has uniform composition throughout the mixture.
Have mixed composition which varies from point to point.
Components are not visible with naked eye.
Components are visible with naked eye.
The entire mixture is in the same phase.
The mixture can be of two phases and can be separated by layers.
Particles have atomic and molecular level size.
Particles have large sizes.
Components cannot be separated easily.
Components can be separated easily.
Note: Milk when not heated is considered as a homogeneous mixture. This is because the various components of milk or nutrients don't seem to form separate layers in it. Milk is actually the homogeneous liquid suspension of fats in water, which in actual terms is heterogeneous mixture by definition. So, the milk is a heterogeneous mixture.