Osmosis Lab Show Introduction: Human blood, at 0.9% salt concentration, is a little less salty than seawater, which has a salt concentration of about 35 parts per thousand (3.5%). If we take seawater as an example of a solution, the salt is called the solute (the particles that are dissolved) and the water is the solvent (the liquid that dissolves the particles). Osmosis is the movement of a solvent across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration. The water (the solvent) can move across the membrane but the dissolved solutes (the sodium and chloride ions that form salt) cannot. In such situations, water will move across the membrane to balance the concentration of the solutes on both sides. Cells tend to lose water (their solvent) in hypertonic environments (where there are more solutes outside than inside the cell) and gain water in hypotonic environments (where there are fewer solutes outside than inside the cell). When solute concentrations are the same on both sides of the cell, there is no net water movement, and the cell is said to be in an isotonic environment. In this lab we will test samples of potato tissue to see how much water they absorb or release in salt solutions of varying concentrations. This gives us an indirect way to measure the osmotic concentration within living cells. Hypo=under, iso=equal, hyper=over Compare initial and final states. Which way did the water move? Why?
Methods:
Click here to go to the calculator page, and thanks to the University of Oklahoma for this useful tool! Results: 1. Record your actual results in a table like this one:
Table 1: Changes in potato mass as a result of immersion in salt solutions. 2. Prepare a graph showing change in mass as a function of % salt. Scale the x-axis of your graph in units of 0.5 percent. The y-axis has a zero line half way up, indicating whether the samples lost or gained weight. You will have to scale the y-axis according to your greatest and smallest changes in mass. Download this Excel spreadsheet if you need help making a graph.Figure 1: Change in mass of potato (g) due to water gain/loss as a function of salt concentration. 3. When completed, use a ruler to draw a straight line of best fit through your six data points, or use the computer to graph your data and calculate the line of best fit. Where the line of best fit crosses the horizontal zero line, draw a vertical line down to the x-axis. This is the point at which the potato is isotonic with its surroundings, and is therefore the estimated salt concentration of the potato. Questions:
In which direction do dissolved molecules also called solutes move in osmosis?In osmosis, water moves from areas of low concentration of solute to areas of high concentration of solute.
In which direction do dissolved molecules also called solutes?Since diffusion moves materials from an area of higher concentration to the lower, it is described as moving solutes "down the concentration gradient".
What direction do molecules move in osmosis?1: Osmosis: In osmosis, water always moves from an area of higher water concentration to one of lower concentration.
In what direction will osmosis water diffusion occur quizlet?Diffusion is the movement of any substance going from high to low concentration. Osmosis is the movement of water, from high concentration of water to a low concentration of water through a selectively permeable membrane.
|