Final answer:
Mixtures thickened with flour are opaque, due to the larger particle size of a suspension, while those thickened with cornstarch or tapioca are translucent because they form a colloid with intermediate-sized particles.
Step-by-step explanation:
Mixtures thickened with cornstarch or tapioca are translucent, which allows light to pass through them, but with some diffusion, whereas mixtures thickened with flour are opaque. This means that they do not allow light to pass through, and objects cannot be clearly seen through the mixture. The reason for this difference in clarity is due to the nature of the particles that make up the mixtures. Flour forms a suspension, which is a heterogeneous mixture of larger particles that appear cloudy and can settle over time. In contrast, cornstarch and tapioca create a colloid, which consists of larger particles when compared to solutions, but these particles still remain dispersed without settling, giving a translucent appearance to the mixture.
The particles in a colloid are intermediate in size between a true solution and a suspension. This is why colloidal mixtures like those made with cornstarch or tapioca exhibit some light-scattering, making them translucent rather than completely transparent like a solution, or opaque like a suspension. An example of a colloidal mixture is milk, where the particles are large enough to scatter light but do not settle out as they would in a suspension.