L.3 OSMOSIS

OBJECTIVES 

Know about the osmosis phenomen and understand the process of it in plasmatic membranes. 

MATERIAL

• Egg.
• Potato. 
• Salt. 
• Distilled water. 
• Vinegar.
• Spatula.
• 600ml. Beaker. 
• Pen. 
• Spoon. 
• Knife. 

PROCEDURE

Egg's procedure:

1. Take a 600ml Beaker and put inside the egg.
2. Cover the egg with vinegar and make note of what's happening. Remember our last experiment. 
3. Clean the beaker and put the egg inside again.
4. Cover it with distilled water. Make note of the volume of solution inside the beaker.

Potato's procedure:

1. Lay out three watch glass.
2. Slice the potato in three parts length wise. Each slice must be of 1,5 cm thick. 
3. Place each slice into a watch glass and make a hole in the center of the potato. 
4. In the first slice hole don't put anything, in the second salt and in the third distilled water.
5. Left this preparation 30 minutes and make note of what's happening. 

RESULTS

Egg experiment

When we immerse the egg in the acetic acid solution, it begin to shed CO2 bubbles. If you take a knife and scratch the egg, the shell dissolves itself completely. When we took the egg to the distilled water solution, the eggs rise in size.

Potato experiment

In this experiment we've been able to see what has happened with the differents solutions in the potato. 

In the NaCl potato, in the potato had appeared water and in the distilled water potato, in the potato the quantity of water had cut down. 

CONCLUSIONS
Egg's conclusions

When the shell is dissolved, it shows at the outside and a web that let pass the dissolvent but not the solute. 

Before we left the egg in the distilled water, the egg weighed more because the inside part of the egg was more concentrated than the outside. So the water start get in the egg and making it bigger. 

Potato's conclusions
The water goes from the less concentrated environment to the most concentrated environment.

In the potato with distilled water, the water had cut down because the distilled water started to get in the inside part of potato and in the potato with NaCl , the water started to go out because the most concentration was outside the potate in the salt.

 Both of them to equilibrate the both sides of  salts concentration. 

QUESTIONS
Egg experiment

1. What is happening when the shells are soaking of acetic acid?  The shell (CaCO3) is dissolved and CO2 is released. 
2. Write the results of the dimensions and weight of the egg before and after immersing it in destilled water: 58 gr before and 62'1 gr after. Write and draw a simple diagram of the water direction. 
   
   
   
   
   

Potato experiment

1. Explain the results of this experiment. In the potato with NaCl, in the potato had appeared water and in the potato distilled water, in the potato the quantity of water had cut down. 
2. Why have we left the first slice without any treatment?  It's called control experiment and we left as it to see if we put nothing in it. 
3. Which are the dependent and independent variables?The independent variable is to put NaCl or distilled water and the dependent is the water absorption or the realease by the potato. 
4. 
   

General questions

1. How can you explain (through the osmosis) the ability of plants roots to draw water from the soil? Because the water has the propiety of cohesion, the plant will absorb the water through the capilarity that water proporcionates it. 
2. What will happen if a saltwater fish is placed in a fresh water (low concentration of salts)aquarium? The fish will absorb water and it will swell.
3. Look at the picture below and explain what is happening to erythrocytes in each situation: In the isotonic solution, the environment will be flaccid, the two environments will be constant, picture 2. In the hypertonic, picture 1, the inside of erythrocytes will lose water because the outside of them is more concentrated. And in the hypotonic, the erythrocytes will swell because the outside is less concentrated and the water will start get in it.