Final answer:
Temperature has a significant effect on the rate of diffusion, where heat increases the rate by boosting molecular movement, while cold decreases it by reducing molecular energy. The correct option is a.
Step-by-step explanation:
The expected effect of temperature on the rate of diffusion is that heat increases the rate. This is because higher temperatures increase the kinetic energy of the molecules, leading to more movement and faster diffusion. Conversely, lower temperatures decrease the energy of molecules, resulting in slower diffusion.
It is important to note that large molecules typically move slower than smaller ones due to their heavier mass, which offers more resistance to motion. Also, the diffusion rate is affected by the density of the solution; as density increases, diffusion tends to decrease because the molecules have less free space to move around.
Finally, greater distance generally slows down diffusion because molecules have to travel further, which takes more time. The correct option is a.