Opening Activity 10/26/15 1.What do we mean when something has a high concentration? 2.What do we mean when something has a low concentration?

Topic: Movement of molecules Essential Question: How and why do the processes of diffusion and osmosis work?

Concentration Amount of solute in a given volume of solvent Concentration refers to how crowded particles are

Concentration Gradient the gradual difference in concentration of a dissolved substance in a solution between a region of high density and one of lower density

Diffusion The movement of molecules from a high concentration to a low concentration – down the concentration gradient

Diffusion [High][Low] concentrated, high energy molecules diffuse, low energy molecules

Diffusion will continue until equilibrium is reached equal distribution of molecules throughout the space. food coloring moves throughout a beaker of water odors smell strong at first and then disappear over time

Diffusion in action Diffusion animation

Osmosis is... A special kind of diffusion involving water molecules moving across a semipermeable membrane – remember what semipermeable means? The cell membrane is semipermeable, but more specifically, it is selectively permeable – Very picky about what can get through Small molecules without a charge Water can pass through freely

Selectively permeable This means that the main way a cell can maintain homeostasis, or balance of its internal environment is by letting in or releasing water through the membrane

What happens to a raisin after sitting in water for a while?  It becomes larger  Why does this happen?

Water molecules have a lower concentration inside the raisin. Outside the raisin, water molecules are crowded. Water molecules diffuse into the raisin by osmosis.

Remember our vocab words? Hypotonic – A solution with a lower concentration of solutes, compared to another solution Hypertonic – A solution with a higher concentration of solutes, compared to another solution Isotonic – A solution with an equal concentration of solutes, compared to another solution

What do those terms have to do with osmosis? Cells will maintain homeostasis by taking in or losing water until equilibrium is reached

Osmosis in cells A hypotonic solution has a lower concentration of solutes, which means it has a higher concentration of water – Water molecules will go from the area where they are more concentrated to where they are less concentrated – A cell sitting in a hypotonic solution will take on water and swell Animal cells can burst Plant cells are protected by the cell wall

Osmosis in cells The solution outside of the cell is 10% salt, which means that the other 90% is water. Inside the cell is 20% salt, which means the other 80% is water. The amount of water outside (90%) is higher than the amount inside (80%), So the water molecules will diffuse into the cell.

Osmosis in cells A hypertonic solution has a higher concentration of solutes, which means a lower concentration of water – Water molecules will go from the area where they are more concentrated to where they are less concentrated – A cell sitting in a hypertonic solution will lose water and shrink

Osmosis in cells The solution outside of the cell is 20% salt, which means that the other 80% is water. Inside the cell is 10% salt, which means the other 90% is water. The amount of water outside (80%) is lower than the amount inside (90%), So the water molecules will diffuse out of the cell.

Osmosis in cells An isotonic solution has the same concentration of solutes, which means the same concentration of water – Water molecules will move back and forth between the two solutions, but there will be no NET movement – A cell sitting in an isotonic solution will not gain or lose water

Osmosis in cells The solution outside of the cell is 10% salt, which means that the other 90% is water. Inside the cell is 10% salt, which means the other 90% is water. The amount of water outside (90%) is equal to the amount inside (90%), So the water molecules will diffuse in and out of the cell equally.

Osmosis cartoon Amoeba Sisters' Osmosis

Wow – lots of vocab! Let’s play a game of Kahoot! Concentration Concentration gradient Diffusion Hypertonic Hypotonic Impermeable Isotonic Osmosis Permeable Selectively permeable Semi-permeable Solute Solution Solvent

Closing Activity/Exit Ticket 1)What are three important points about the movement of molecules? 2)What is one thing that is still going around in your head?