P.5 GLÚCIDS

OBJECTIVES

Identify different sugars and reducing glucids. Understand the relation between structures and properties. 

 

MATERIAL 

Water

Lugol

Fehling A and B.

Beaker (to put distilled water)

Test tubes.

Rack.

Spoon.

Distilled Water.

Different glucids:  Maltose, sucrose, glucose, lactose and starch.

Dropper.

Stove.

PROCEDURE

Testing the flavour of the glucids, which were sweet.

Then prepare 10 essay tubes divided in two racks, with different type of glucids.

Seeing if it’s soluble or not:  test if the different glucids are soluble in distilled water, adding 2 ml of water.

FEHLING TEST: add to different glucids solution at the first rack, which contains 2 ml of water; add in each glucid essay tube 2ml of Fehling A and 2 ml of Fehling B. Finally, warn the tubes and see if the colour changes from blue to red-brown.

It has to be a control tube, only with distilled water, Fehling A and Fehling B, colour blue.

LUGOL TEST:  form another rack with 5 tubes with each type of glucids (different saccharides), adding first 5 ml of distilled water.  Put on in each tube 2 drops of Lugol.

It has to be a control tube, only with distilled water and two drops of Lugol.

RESULTS 

	MALTOSA	LACTOSA	GLUCOSE	SUCROSE	STARCH
Sweet	No.	Yes.	Yes.	Yes.	No.
Solubility	Yes.	Yes.	Yes.	Yes.	No.
Fehling	Yes.	Yes.	Yes.	No.	No.
Lugol	No.	No.	No.	No.	Yes.
Mono/di/poli	Di.	Di.	Mono.	Di.	Poli.

CONCLUSIONS 

FEHLING TEST

The glucids (maltose, lactose, glucose and sucrose) are oxidized and they reduce the Copper Sulphate of Felhings (A and B). The Copper (++) is reduced to copper (+). We can observe it because the change of colour changes from blue to red-brown. The sucrose isn’t a reducing disaccharide because of the link (1-2) that don’t let any group carbonyl free and the starch isn’t a reducing sugar because is a polysaccharide (negative).

LUGOL TEST

Lugol is formed by iodine, this reacts with starch and then the colour of the solution changes from yellow to black.  

P4. PH

OBJECTIVES

Can see pH and measure different pH substances based on mixing water and lemon. 

MATERIAL 

• Test tubes
• Lemon
• Water
• pH paper detectors
• A beaker. 
• A pipette. 

PROCEDURE 

1. We cut the lemon in half.
2. We squeeze the two pieces  to get lemon juice.
3. Take the pipette for the amounts in ml below. 
4. When we have the tubes with all quantities mixed, add the paper measuring pH to see which number has each mixture. 

Tests tube	H2O (ml)	Lemon (ml)	PH ?
1	1	5
2	2	4
3	3	3
4	4	2

RESULTS

Tests tube	H2O (ml)	Lemon (ml)	PH
1	1	5	3(a tots)
2	2	4
3	3	3
4	4	2

CONCLUSION 

The quantity of water doesn't determinate if the pH is acid (between 1 and 7) or basic (8 and 14), the neutral pH is 7. 
So as we put so much water doesn't mean that the mixture would be more basic. 

QUESTIONS 

1. Which is the dependent variable?  It's the pH.
2. Which is the independent variable? The lemon. 
3. Which is the control? The control is the tub that contains the same quantity of lemon as water. 
4. Which pH do you think that in blood? And in gastric juice? The pH in blood is between 7'35 and 7'45, it has to be neutral, if it was acid we would die; and in the gastric juice is between 0'9 and 1'5, it has to be acid to dissolve different substances. 

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. 

L.2 MINERALS SALTS IN ORGANIMS

OBJECTIVES
We want to see how much CaCO3 there is in these bones. 
Identify mineral sals in organism and understand the function of inorganic biomolecules in sketal structures. 

MATERIAL

• Acetic Acid
• Chicken bones
• Mollusc's shells 
• Baker 
• Tongs

PROCEDIMENT
Chicken bones

1. Carefully clean and cut ad much of the meat away from the chicken thin bone as possible.
2. Examine the flexibility of the bone by trying to bend it with your fingers.
3. Take a baker an add vinegar 
4. Take the bones and drop them in the acid acetic solution that you have made.
5. Leave it 24 hours and see what happens to the bone. 
6. Remove the bones from the vinegar with a tong and soak them with water.

Mollusks shells

1. Take another baker and make the same acid acetic solution. 
2. Put inside some shells and make note of what's happening. 

RESULTS

In the case of the bones, the bone is dissolved by calcium salts and just left the conjunctive tissue. The bone is soft, as the salts responsible of the strength of it. 

  

In the case of the shells, the acetic acid dissolves calcium carbonate, so that, the shell loses completely its form. 

QUESTIONS
1, Write the reaction that takes when the acid acetic reacts with the calcium carbonate. 

CaCO₃ (Calcium Carbonate) + CH₃COOH (Acetic from the vinegar) --> Ca (CH₃COO)₂ (calcium acetate)  + H₂O + CO₂

2. What is happening when the shells are soaking of acetic acid? What  are the bubbles that you can see?
Calcium stays in the shells and the Carbon dioxide unpins from it in the way of bubbles.
3. What is happening to the bone after some days of soaking it in acetic acid? Why is the bone flexible now?
Because the Calcium Carbonate has unpinned from the bones and then, collagen , that is soft, has remained in it.  
4. So, what is the function of the calcium carbonate in the skeletal structures.
Calcium Carbonate gives strength and resistance to bones.  
5. Increases in carbon dioxide to the atmosphere from the burning fossil fuels and deforestation threaten to change the chemistry of the seas. Evidence suggests that this increase in atmospheric carbon dioxide is lowering the PH of the oceans in a process called ocean acidification. How can acidification affects corals reefs.

It will happen the same as in the experiment before.