Diffusion moves particles from areas of higher concentration to areas of lower concentration, driven by random molecular motion. Osmosis is the specific case where water diffuses across a selectively permeable membrane from the side with lower solute concentration to the side with higher solute concentration. This statement matches that distinction: diffusion is described as moving from high to low concentration, and osmosis as water diffusion across a semipermeable membrane. Both processes are passive and require no energy input. The other choices misstate key points: diffusion isn’t energy-dependent, osmosis requires a membrane, and diffusion occurs in gases and liquids as well as solids.

Phase change is a change of state without changing the chemical identity of the substance. When a solid becomes a liquid or a liquid becomes a gas (or the reverse), energy is used to rearrange how the molecules are arranged and move, but the molecules themselves stay the same. There’s no new substance formed, just a different form of the same material—for example, ice melting into liquid water or water boiling into steam. Other terms describe chemical changes, where bonds are broken and new substances are produced, such as oxidation (electron transfer) or hydrolysis (reaction with water breaking bonds).

Liquid turning into gas is evaporation. In this process, molecules at the surface gain enough energy to overcome the attractive forces holding them in the liquid and escape into the air as vapor. Evaporation can occur at any temperature below the liquid’s boiling point and tends to cool the remaining liquid because the highest-energy molecules leave first. This is different from boiling, which happens throughout the liquid at a specific temperature when vapor pressure matches the surrounding pressure. Condensation is the reverse (gas to liquid), sublimation is solid to gas, and deposition is gas to solid. An everyday example is a puddle gradually drying up as it evaporates.

Random assignment ensures each participant has the same chance of ending up in any group, which helps create comparable groups at the start of an experiment. By giving everyone an equal opportunity for assignment—think of a coin flip, a random number, or a shuffled list—you minimize selection bias and other preexisting differences that could influence outcomes. If groups start out similar, any differences observed after the intervention are more likely due to the treatment itself rather than who happened to be in each group. Blinding, on the other hand, hides group membership from participants to reduce expectancy or reporting biases, but it doesn’t affect how participants are assigned. Double-blinding extends this concealment to researchers collecting outcomes. Stratification involves dividing participants into subgroups based on certain characteristics and then randomizing within those subgroups to ensure balanced representation across groups; it helps balance known factors but is not the mechanism that guarantees equal assignment probabilities across the entire sample.