Main Answer:
The example of a heterogeneous mixture among the given options is d. coffee.
Therefore, the correct answer is d. coffee.
Step-by-step explanation:
Coffee is a classic example of a heterogeneous mixture because it is composed of various components that do not uniformly distribute throughout the mixture. When you make a cup of coffee, it consists of water, coffee grounds, oils, and other solutes that don't dissolve completely. The distinct layers and variations in concentration make coffee a heterogeneous mixture.
In a cup of coffee, the water serves as the solvent, and the coffee grounds, oils, and other compounds act as solutes. Unlike a homogeneous mixture, such as salt dissolved in water (option b), where the components form a single, uniform phase, the components in coffee maintain their individual properties and don't merge seamlessly. The visual differences, like the suspended coffee grounds, are observable, highlighting the heterogeneity of the mixture.
Similarly, options a, c, and e don't represent heterogeneous mixtures because sand mixed with oil (a) could potentially settle into layers, but it has the potential to form a homogeneous mixture if the particles are finely dispersed. Air (c) is a homogeneous mixture of gases, and vinegar (e) is a solution of acetic acid in water, which also constitutes a homogeneous mixture.
In conclusion, coffee's composition and the visible differences in its components establish it as an example of a heterogeneous mixture.
Therefore, the correct answer is d. coffee.