Peter was preparing some potatoes for cooking. He put some water in a pot and added some salt. He cut up the potatoes and put them in the salt solution. Then the telephone rang and he spent 30 minutes talking to George. When he returned to put the potatoes on the stove they were flaccid (soft). Explain what happened to the potatoes. The concentration of free-moving water molecules is higher in potato cells, the cytoplasm of the cell is hypersonic. The water molecule will flow from higher concentration to lower concentration, so that they get out of potato cells through osmosis.

The plasma membrane of plant cell will collapse as the water inside the cell become less and less, that cause polynomials and the cell become flaccid. 2. A salt water fish may die if placed in fresh water. Why? In order to keep an isotonic condition, the salt water fish’s cells have the same concentration with salt water. When they are placed in fresh water, concentration of water molecule in fresh water is higher than that in fish’s cell, fresh water is hypersonic. Due to osmosis, the water molecule will move from fresh water to the cell. The saltwater fish has no mechanism to get the extra water out.

The cell will explode, or salt water fish can adapt that much water inside their body, and they may die. 3. Explain why a salt solution is a good antiseptic (kills bacteria)? The concentration of water molecules is higher inside the bacteria, and the cytoplasm of bacteria is hypersonic. Due to osmosis, the water molecule will move from bacteria to salt solution. The bacterial cells will shrivel and die, as water leaving the cell. 4. A small amount of fertilizer will make the grass of a lawn grow. Too much fertilizer will “burn” kill the grass. Why? Using too much fertilizer will create a hypotonic rounding for grass cell.

The water molecule will move out of the grass, and cause polynomials of cell. The grass will then become yellow, flaccid, and die. 5. The red blood cells in our blood are suspended in a solution called blood plasma. Is the blood plasma isotonic, hypersonic or hypotonic? Explain your answer. Blood plasma is isotonic. If it’s hypersonic, water molecules inside the blood cell will go out and the cell can’t carry oxygen since it shrinks. If it’s hypotonic, the water molecules will move from blood plasma to red blood cell, and the cell will expand and explode.

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Only when the blood plasma is isotonic, there is no net movement of water molecules. 6. How can fish live in salt water without becoming dehydrated? Fish solve this problem by drinking the salty water, retaining the water, and excreting the salts. They have special chloride excreting cells in the gills which actively pump salts out of the body. Conclusion: Osmosis was observed by measuring the mass and looking at the physical change of gummy bears in different surroundings in this lab. The control was weigh boat A, there was no water or solution in it. The percent change in mass was 0. 4%, and it was neglected compare to results of other three samples. The gummy bear had no physical change. Weigh boat B had ml distilled water in it. The percent change in mass was 493%, the gummy bear expanded to 3 times of original, and it was not elastic. Weigh boat C had ml tap water. The percent change in mass was 460%. The gummy bear expanded to 2. 5 times of original. Weigh boat D had ml distilled water and 0. G salt in it. The percent change in mass was 134%. The gummy bear expanded to 1. 5 times of original, and it was still quite elastic.

If the concentration of eater molecules in the solution is higher, then the weight of gummy bear will increase, vice versa. Because the water molecule move out of gummy bear due to the concentration gradient of water molecules. The concentrations of water molecules were higher in distilled water, tap water, and salt solution with 0. G salt. So that the water molecules flowed from outside to inside of gummy bears, and their masses increased. Surprisingly, the concentration of water molecules was higher in weigh boat D. The prediction was that the gummy bear in weigh boat D would become smaller.

However the result suggest that the mass increase. That showed the concentration of sugars in gummy bears was higher than ml salt solution with 0. G salt. Another interesting finding was that the mass of control increased a little bit. It might because of different electronic balance. A coming question is that if the time of experiment is long enough, will the gummy bears, especially the one in distilled water explode? During this experiment, there were some sources of errors. When the masses of gummy bears were being measured after 2 days, they were really fragile.

The gummy bears were broken into small pieces during the process of transporting hem to another weigh boat. Some tiny little pieces were left in the original weigh boat. That made the result smaller than it should be. Some water inside the gummy bear were lost during this process as well. There were also some extra water was transported in to the weigh boat, and that made the result higher than it should be. To improve this experiment, the amount of salts in weigh boat D has to be increased. The concentration of salt is not high enough to make the gummy bear shrink. The mass of salt can be changed to 2. G in order to get a better result.

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