OSMOSIS. After osmosis has taken place, both solutions have the same concentration of solute.

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1 BIOLOGY: OSMOSIS

2 OSMOSIS Osmosis is the physical process by which, in a solution, the concentration of solute is regulated by the movement of the solvent, water, through a semipermeable membrane (permeable to the solvent but not to the solute). This process takes place because matter always tends to find its equilibrium, and it happens with no appliance of energy. After osmosis has taken place, both solutions have the same concentration of solute.

Three different things can happen: If the concentration of solutes is the same inside and outside the cell, the movement of water is balanced

3 Osmosis also takes place in cells. In this case, the concentration of solutes such as sugars or salts is regulated by water as solvent, which moves through the cell membrane. Three different things can happen: If the concentration of solutes is the same inside and outside the cell, the movement of water is balanced (isotonic). If the concentration of solutes is higher inside the cell than outside, water enters the cell and it swells (hypotonic). If the concentration of solutes is lower inside the cell than outside, waters gets out of the cell and it shrinks (hypertonic). OSMOSIS IN CELLS

4 OSMOSIS EXPERIMENT Material needed: 3 beakers 1 small container A scale A potato, a raisin and a carrot Salt Water A knife

5 OSMOSIS EXPERIMENT Procedure: 1. Measure the weight of salt that you are going to pour on each beaker (30, 20 and 5 grams respectively). 2. Pour the same volume of water in the beakers (90 ml), then add the corresponding quantity of salt (make sure you distinguish the different solutions by labeling them!). Measure the volume of the solutions. 3. Measure the molarity of the solutions (moles of NaCl/volume of solution). 4. Peal the potato and the carrot. Then, measure the weight of the raisin, the carrot and the potato, and write it down. 5. Submerge the three of them in the corresponding solutions (the potato, in the most saturated one, and the raisin in the most diluted one). 5. After 48 hours, take them out of the water, dry them, and weight them again. 6. Calculate the differences in weight and the percentage of variation.

6 OSMOSIS EXPERIMENT: THE SCIENTIFIC METHOD Identify the problem: we have to prove the process of osmosis with a biological semipermeable membrane. We have 48 hours to do it. Hypothesis: if we place a carrot, a potato or a raisin in salty water, after 48hours, they will have dried up because water will have got out of them due to osmosis. Conclusion: So, from this experiment we can conclude that due to the process of osmosis, water moves through semipermeable membranes in order to balance the concentration of solutes.

7 POTATO TEST WEIGHT OF SOLVENT/SOLUTE (gr) WEIGHT (gr) OF 1 MOLE QUANTITY OF MATTER (moles) VOLUME OF SOLUTION (ml) WATER (H 2 O) SALT (NaCl) (90+14) MOLARITY = QUANTITY OF SOLUTE (moles) = 0.5 = 4.8M VOLUME OF DISSOLUTION (liters) Salt Density: 2160 gr/l INITIAL WEIGHT FINAL WEIGHT PERCENTAGE OF WEIGHT THAT REMAINS PERCENTAGE OF WEIGHT LOST 103 gr 85.1 gr 82.62% 17.37%

8 CARROT TEST WEIGHT OF SOLVENT/SOLUTE (gr) WEIGHT (gr) OF 1 MOLE QUANTITY OF MATTER (moles) VOLUME OF SOLUTION (ml) WATER (H 2 O) SALT (NaCl) (90+9) MOLARITY = QUANTITY OF SOLUTE (moles) VOLUME OF DISSOLUTION (liters) = = 3.53M Salt Density: 2160 gr/l INITIAL WEIGHT FINAL WEIGHT PERCENTAGE OF WEIGHT THAT REMAINS PERCENTAGE OF WEIGHT LOST 66 gr 50 gr 75.75% 24.25%

9 RAISIN TEST WEIGHT OF SOLVENT/SOLUTE (gr) WEIGHT (gr) OF 1 MOLE QUANTITY OF MATTER (moles) VOLUME OF SOLUTION (ml) WATER (H 2 O) SALT (NaCl) (90+2) MOLARITY = QUANTITY OF SOLUTE (moles) VOLUME OF DISSOLUTION (liters) = = 0.92M Salt Density: 2160 gr/l INITIAL WEIGHT FINAL WEIGHT PERCENTAGE OF WEIGHT THAT INCREASES PERCENTAGE OF WEIGHT GAINED 0.7 gr 1.1 gr % 57.14%

DURING AND AFTER THE EXPERIMENT PROBLEMS WE HAD DURING THE EXPERIEMNT: When we wanted to put the carrot and the potato into the beakers, we realized they were too big, so we had to cut them into

This means that our first hypothesis was partly wrong. As expected, water from potato and the carrot had gone out of them because the concentration of salts was higher outside than inside them.

10 DURING AND AFTER THE EXPERIMENT PROBLEMS WE HAD DURING THE EXPERIEMNT: When we wanted to put the carrot and the potato into the beakers, we realized they were too big, so we had to cut them into pieces before. AFTER THE EXPERIMENT: Re-hypothesis: After 48 hours, we saw that both the potato and the carrot had decreased in mass, but the raisin had won weight. This means that our first hypothesis was partly wrong. As expected, water from potato and the carrot had gone out of them because the concentration of salts was higher outside than inside them. However, contrary to what we had thought, the raisin had increased in weight. This may be because the concentration of the solution (0.92M) wasn t enough to make water of the raisin get out of it; so it happened right the opposite, water entered the raisin because the concentration there was higher. Further researches: We could make another experiment to find out the needed concentration of solution to make water get out of the raisin.

11 DONE BY: KATERINA KOZITSKI GARCÍA PAULA SÁEZ SOTO ANDREA SÁNCHEZ SÁNCHEZ INÉS UTRERO BORLAZ RUBÉN VICENTE LÓPEZ 4ºA h OSMOSIS Subject: Biology and Geology Teacher: Maribel Cuenca Asenjo High School: I.E.S.B. Ciudad de los Poetas Tuesday, 21 st of January 2014

Water Potential - AP SBI4UP

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