Answer:
1. Independent variables: temperature, distance, concentration gradient
Dependent variables: The water and food dye because it is being used to measure the rate of diffusion
2. The tube with a higher temperature would have a higher rate of diffusion than a tube with a lower temperature because introduction of heat helps the particles move farther and faster apart
3. A controlled variable can be the amount of food dye used in each tube so you can record an accurate rate of which the food die gets diffused.
