SECOND EXPERIMENT: Osmosis

• Introduction:

Osmosis is the spontaneous movement of solvent molecules through a semipermeable membrane into a regino of higher solute concentration (hypertonic) in the direction that tends to equalize the solute concentrations on the two sides.
When the extracelular concentration is hypertonic, water moves out of the cell and the cell becomes flaccid: PLASMOLYSIS.
When the extracellular concentration is hypotinc, water moves inside the cell and it becomes TURGID.

• Material:

1. Egg
2. Potatoe
3. Salt
4. Distilled water
5. Acetic acid (or vinegar)
6. Spatula
7. 600 ml Beaker
8. 3 Clock glass
9. Pen
10. Spoon
11. Knife

• Procedure:

Egg: this experiment will be divided in two days.

Under the hard outer shell of a chicken egg is semipermeable membrane that allows air and moisture to pass through. Because water molecules can move into and out of the egg but larger molcules cannot, the semipermeable egg membrane allows for an explorations of concepts of diffusion and osmosis.

1st Day:
Before the egg osmosis experiment could begin, the egg's hard outer shell must be removed. Let's start with this:

1. Take a 600 ml beaker and put inside the egg.
2. Cover the egg with vinegar and make note of what's happening. Remember our last experiment!

Once the egg's shell is removed and the egg is rinsed dry and clean, measuer and weigh the egg. Record the dimensions of each egg in a table.


     3. Clean the beaker and put the egg inside again.
     4. Cover it with distilled water. Make note the volumen of solution inside the beaker.

2nd Day:

      5. Left the egg one day in the distilled water. After about a day, carefully remove the egg using a spoon. Rinse the egg with water and let it dry.
      6. Measure again the dimensions and records its weight.
      7. Make note of the solutions volume in the beaker and notice if there has been any difference.
      8. Observe the results and write your conclusions in your lab worsheet.

Potato:

1. Lay out three watch glass.
2. Slice the potato in three parts lengthwise. Each slice must be of 1'5 cm thick
3. Place each slice onto a watch glass and make a hole in the middle of each slice. NOTE: the hole does not have to cross the slice!
4. In the first slice hole, don't put anything. The second fill it with salt and the third with distilled water.
5. Left this preparation 30 minutes and makes note of what is happening.

• Resolts or Observations:

Egg:
When put the egg in shell the acetic acid and desace semipermeable membrane disappears and remains. Put the egg in distilled water and await the outcome for about one day, we can see that the egg has puffed up and has gained weight. Later we put the egg in water mixed with a high salt concentration and can see that the egg has been deflated and lost weight.

Potato:
Cut three pieces of potato, and put them in the three watch glasses. In a piece we do nothing, another put salt and put distilled water in another.
In the piece that we do not put anything on potato oxidized in the piece we put salt water and expels potato gets soft, and the piece that we distilled potato absorbs water and becomes turgid.

• Conclutions:

The shell is undone by the following reaction: CaCO3 + CH3COOH = Ca (CH3COO) 2 + CO2.
The egg to be swollen in distilled water because the higher salt concentration inside the egg and water enters inside. When we place the egg in water with a high concentration egg devido deflates within the egg that is a lower concentration of salt outside.
All this is given to a balance of salts beyond.

• Questions:

1. What is happening when the shells are soaking of acetic acid? We see some bubbles the reactions: CaCO3+CH3COOH=Ca(CH3COO)2+CO2.
2. Explain the results of this experiment: The control grup there's no change. The salt grup expulsed water and lose turgense. The distilled grup absorbe water and win turgense.
3. Why have we left the first slice without any treatment (salt or distilled water)? To compare the all resolts.
4. Wich are the dependent and independent variables? The variable independent treatment(salt and distilled water) and variable dependent the form of cells or presence of water.
5. How can you explain (throught osmosis) the ability of plant roots to draw water from the soil?The salt concentration is higher in the cells and the water goes up because there was a balance.
6. What will it happen if a saltwater fish is placed in a freshwater (low concentration of salts) aquarium? It will die.
7. Look the image you have below and explain what is happening to the erytrocytes in each situations:In the first photo shows a case hypotonic, and is a plasmolysis in the second case Isotonic and hypertonic third case where a picture is turgidity.