Diffusion

• Molecules on the move - Diffusion
• Diffusion is the spreading out of particles from an area of high concentration to an area of low concentration.
• Diffusion happens in both solutions and gases because the particles in these substances are free to move about randomly.
• The bigger the concentration gradient (the difference in concentration) the faster the diffusion rate
• A higher temperature will also give a faster diffusion rate because the particles have more energy, so move around faster.
• Factors affecting diffusion
• The bigger the concentration gradient (the difference in concentration) the faster the diffusion rate
• A higher temperature will also give a faster diffusion rate because the particles have more energy, so move around faster.
• Cell membranes
• They hold the cell together but they let stuff in and out as well.
• Dissolved substances can move in and out by diffusion.
• Only very small molecules can diffuse through cell membranes such as oxygen, glucose, amino acids and water.
• Big molecules like starch and proteins can't fit through the membrane.
• Particles flow through the cell membrane from where there's an area of high to low concentration
• They only move about randomly so they go both ways - but if there's more on one side of the membrane there's a net movement from that side.
• The higher the surface area of the membrane, the faster the diffusion rate, because more particles can pass through at once.
• Factors affecting diffusion
• Question - A student adds a drop of ink to a glass of cold water. A. what will the student observe to happen to the drop of ink, B. How might the observation differ if the ink was added to a glass of warm water?
• A.The ink will diffuse and spread out through the water. This is because the ink particles will move from where is a higher concentration of them (the drop of ink) to where there is a lower concentration of them (the surrounding water).
• B. The ink particles will diffuse/spread out faster.