The observation that the spread of color in the warm water (B) is faster than in the cold water (A) can be explained by the fact that temperature affects the rate of diffusion. Diffusion is the process by which particles in a substance move from an area of high concentration to an area of low concentration until they are evenly distributed.
In warmer water, the water molecules have more kinetic energy, which means they move around faster and collide more frequently with the potassium permanganate particles. This increases the rate of diffusion, causing the color to spread faster.
In colder water, the water molecules have less kinetic energy, so they move around more slowly and collide less frequently with the potassium permanganate particles. This decreases the rate of diffusion, causing the color to spread more slowly.
Therefore, the temperature difference between the two beakers is the reason for the faster spread of color in the warm water (B) than in the cold water (A).