Diffusion Processes PDF

Diffusion Everything is made of atoms, molecules and ions. The higher the temperature is, the faster they move. Why? Because of Kinetic Energy- the energy from movement. Higher the K.E, faster the diffusion. (Imagine a locked room full of 50 of you and I switch off the AC. The ho...

Diffusion Everything is made of atoms, molecules and ions. The higher the temperature is, the faster they move. Why? Because of Kinetic Energy- the energy from movement. Higher the K.E, faster the diffusion. (Imagine a locked room full of 50 of you and I switch off the AC. The hotter it is, the more you are going to twitter around uncomfortably.) Solids Particles are tightly packed by attractive forces. They do not move but vibrate about a fixed position. They have a fixed shape and volume. Liquids Particles move more freely and randomly. Have an irregular arrangement. But they still stay in contact with each other. No fixed shape, but fixed volume. Gases Particles move even more freely and randomly With no attractive forces at all. So no fixed shape or volume. Solute - Substances that get dissolved Eg: Sugar Solvent - The liquid that does the dissolving Eg: Water is a Universal Solvent *The word concentration can be defined using the words solute and solvent. Eg: High conc - When there are high numbers of solute particles in a solvent. Low conc- when there are low numbers of solute particles in a solvent. Diffusion Definition Remember these 3 points! The net movement (overall movement) of particles From a region of higher concentration to a region of lower concentration Down a concentration gradient. *This is a passive process - does not require energy to occur. Kinetic energy of the particles is enough. Important processes that need Diffusion 1. Photosynthesis in Leaves - O2 is produced in the leaf as a waste product of photosynth. ⸫ there is a high conc of O2 inside leaf ⸫ O2 diffuses from High conc (inside leaf) to low conc (outside leaf) - CO2 diffuses in the opposite manner. *How is the leaf always needing CO2 even though it is getting CO2 by diffusion?? The CO2 that is absorbed is always getting used up in photosynthesis to make glucose! That is how the concentration gradient is maintained. 2. Gas exchange in the lungs - O2 diffuses from lungs (high conc) into blood (low conc) - CO2 diffuses from blood (high conc) into lungs (low conc) 3. Diffusion in & out of Cells - A cell is surrounded by a cell membrane which is semi-permeable. *Semi-permeable membrane is a membrane that allows only some substances pass through it. Also called partially permeable or selectively permeable. Fully permeable or freely permeable allows alllllll substances through (eg: Cell Wall). 4. Ileum/Small Intestine - After digestion occurs, the nutrients are absorbed into the blood in the lower end of the small intestine, called the Ileum. Diffusion allows the movement of the nutrient from a high conc (inside ileum) to a low conc (into the blood). Thus the nutrients you eat, use diffusion to enter the blood and enter every one of your cells! Diffusion takes place with smells such as perfumes, rotten eggs, dyes, paint-mixing. Everything but WATER uses diffusion! Factors that Affect the Rate of Diffusion Some features can either speed up or slow down diffusion speed: 1.Temperature - higher the temp, higher the Kinetic energy so higher the movement and higher the diffusion rate. 2. Surface Area to volume ratio - Higher the surface area to volume ratio available, the faster the diffusion rate. *SA : VR is a fraction of the surface area of an object and its volume. Bigger the ratio, faster the diffusion rate 3. Diffusion Distance - Higher the thickness of a membrane, slower the diffusion rate. So negative correlation. 4. Concentration Gradient - Higher the conc. Gradient, the faster the diffusion rate. Concentration gradient - is the difference between concentrations of 2 regions. The Gradient can be imagined as a slope. The steeper the gradient, the faster the particles will roll down the slope.