b) Pippa looks at diffusion through a microscope. She finds that the substance diffuses much more rapidly in agar gel than it does in water. What could be the reason for this? c) Pippa writes a rep

In any experiment, it's crucial to control other variables to ensure the reliability and validity of results. For Pippa's investigation on the speed of diffusion of four colored substances in agar gel, here are the reasons why she must control the other variables: 1. Type of agar gel: Different types or brands of agar gel may have different properties such as density and permeability. This can affect the speed of diffusion, so keeping the agar gel type constant allows Pippa to eliminate this from affecting the results. 2. Temperature of agar gel: The Temperature can significantly impact the rate of diffusion. Increasing temperature generally increases diffusion as it provides more energy for particles to move. Therefore, by keeping the temperature of the agar gel constant, Pippa is removing the potential influence this could have on the speed of diffusion. 3. Substance that diffuses: Different substances may diffuse at different rates due to their size, shape, or chemical properties. Controlling this variable means she can be sure that any differences in diffusion speed are not because of the nature of the substances. 4. Distance from top of agar gel to bottom of color: The diffusion distance can also influence the time it takes for substances to diffuse. A longer distance may require more time for a substance to diffuse. By controlling this, Pippa can ensure the dissimilarities in diffusion speed are not due to different diffusion distances. 5. Time for which the solids are left to diffuse: It's also important to control the time to make sure all substances have an equal amount of time to diffuse. By controlling all these variables, Pippa can make a fair comparison of the diffusion speeds of the different colored substances, and also be more confident that any differences she observes are due to the different substances, not other factors.