iGCSE Chemistry (0620) Core:1.2 Diffusion: Exam Style Questions Paper 1- New Syllabus
▶️ Answer/Explanation
Detailed solution:
Diffusion means that particles of nitrogen dioxide and air will mix together because of their constant random motion. Even though nitrogen dioxide is denser than air, given a full 24 hours, the particles will eventually spread evenly throughout both gas jars. The final result is a uniform mixture that looks like a lighter, even brown colour across the entire space of both jars, which is exactly what diagram D shows.
▶️ Answer/Explanation
Detailed solution:
When a sodium chloride crystal is dropped into water, the ionic bonds in the crystal lattice are broken as the water molecules surround the $\text{Na}^+$ and $\text{Cl}^-$ ions, so dissolving occurs. Once dissolved, the sodium and chloride ions spread out from an area of high concentration to areas of lower concentration until they are evenly distributed throughout the water, which is the process of diffusion. So both dissolving and diffusion take place, making option A the correct answer.
▶️ Answer/Explanation
Detailed solution:
Diffusion is the gradual movement of particles from a region of high concentration to a region of low concentration, and it occurs at different speeds in different states of matter. Diffusion in liquids is significantly slower than in gases because the particles are much closer together and experience more collisions. A substance moving very slowly from an area of high concentration to low concentration through a liquid perfectly describes this process. Freezing and melting are state changes, not concentration-driven movement, while diffusion through the air would be much faster, not very slow as the question specifies.