1. The dye spread across the filter paper because of diffusion. The dye molecules moved from the area of higher concentration (the drop of dye) to the area of lower concentration (the rest of the filter paper) until the dye was evenly distributed.

2. If the filter paper was heated, the rate of diffusion of the dye would increase. Heating the filter paper increases the kinetic energy of the dye molecules. This means they will move faster and diffuse more quickly across the paper. A higher temperature also reduces the viscosity of the filter paper, making it easier for the dye molecules to move through it.

Diffusion is the net movement of particles from a region of high concentration to a region of low concentration. Several factors influence the rate of diffusion:

• Surface Area: A larger surface area allows for more particles to diffuse across the membrane simultaneously, increasing the overall rate. For example, in the lungs, alveoli have a vast surface area to facilitate rapid oxygen diffusion into the blood.
• Concentration Gradient: The steeper the concentration gradient (the greater the difference in concentration), the faster the rate of diffusion. A larger difference in concentration drives particles more rapidly from the high concentration area to the low concentration area.
• Temperature: Higher temperatures increase the kinetic energy of particles. This means particles move faster and collide more frequently, leading to a faster rate of diffusion. However, very high temperatures can damage biological molecules, so there's an optimal temperature range.
• Distance: The shorter the distance the particles need to travel, the faster the rate of diffusion. The time it takes for particles to diffuse is inversely proportional to the distance.

These factors often work together. For instance, a larger surface area with a steep concentration gradient and a moderate temperature will result in the fastest rate of diffusion.

Experiment: Demonstrating Diffusion of Solutes

Materials:

• Two identical containers (e.g., clear plastic bottles)
• Water
• Sugar (e.g., table sugar)
• Two droppers or pipettes
• A ruler or measuring tape

Procedure:

1. Fill both containers with the same amount of water.
2. Dissolve a known amount of sugar in one container to create a sugar solution (high solute concentration). Leave the other container with pure water (low solute concentration).
3. Use a dropper to carefully add a few drops of the sugar solution to one container and a few drops of the pure water to the other container. Ensure the drops are added at the same time and from the same height to minimize initial variations.
4. Observe the containers over a period of 30-60 minutes.
5. Measure the water level in each container at regular intervals (e.g., every 10 minutes) using a ruler or measuring tape.

Variables:

• Controlled Variables: Amount of water in each container, amount of sugar in the sugar solution, temperature of the water, size of the containers, type of container.
• Variables to Observe: Water level in each container over time.

Expected Results and Explanation:

Over time, you should observe that the water level in the container with the pure water increases, while the water level in the container with the sugar solution decreases. This is because water molecules will diffuse from the area of high water concentration (pure water) to the area of low water concentration (sugar solution) across the semi-permeable membrane (the container walls). This movement of water is driven by the difference in water potential. The sugar molecules are too large to easily cross the container walls, so the water molecules effectively carry the sugar with them.

These results support the theory of diffusion because they demonstrate the net movement of particles from a region of high concentration to a region of low concentration. The diffusion of water across the container walls, driven by the concentration gradient created by the sugar solution, clearly illustrates the principle of diffusion in action. The experiment shows that solutes create a water potential gradient, driving the diffusion of water and demonstrating how diffusion is essential for maintaining equilibrium.