L7.LIPIDS PROPERTIES

OBJECTIVES:
1) Test the solubility of lipids.
2) Identify lipids in liquids compounds.
3) Understand what are an emulsion and the effect of detergents.

MATERIAL:

• test tubes

• 250mL beaker

• Water

• Test tube rack

• Cellulose paper

• Dropper

• Scissors

• Glass rod

• Oil

• Soap (detergent)

• ether

• ethanol

• sudan III

• MILK with different fat content: full-cream, skimmed milk and soymilk.

PROCEDURES:

SOLUBILITY OF SOME LIPIDS

1. Clean and dry three test tubes. Label as W (water), ethanol (E) and PE (ether).
2. Add 3 drops of oleic acid to 3 small test tubes.
3. Add 1mL of water in in the first test tube (W)
4. Add 1mL of ethanol in the second test tube (E)
5. Add 1mL of ether in the third test tube (PE)
6. Shake carefully each test tube

LIPIDS IDENTIFICATION:

TRANSLUCENT MARK

7. Cut two piece of cellulose paper.
8. Put 1 drop of water in the first squared piece. 
9. Put 1 drop of oil in the second squared piece. 

SUDAN III DYE

10. In first place take the W test tube of the first experiment and add 2 drops of Sudan III.
11. After  took another 4 test tube( with different fat content)

o   In first test tube one type of milk full-cream

o   In the second tube another type of milk skimmed

o   In the third tube another type of milk soya milk

o   In the last test tube we put soda (S) 

o   And finally add 2 drops of Sudan III in each of 4 test tube and observe the results.

   

    EMULSION AND EFFECT OF DETERGENT

    In first place we need to take a 250ml beaker and put 100ml of water. 

    Add 1ml of olive oil. With a glass rod stir the mixture vigorously and let it stand for a few minutes.

    Observe and make note of what is happening.

    Finally we added 2 drops of soap and stir the mixture again. Let it stand for a few minutes and notice the differences between both mixtures.

RESULTS:

WATER+OIL-> NO SOLUBLE

ETER+OIL   -> SOLUBLE

PE+ OIL-> SOLUBLE

SKIMMED MILK: The solution stain soft orange

Semi-skimmed milk: The solution stain medium orange

Soymilk: It doesn’t change the colour.

WATER AND OIL FORM A TEMPORARY EMULSION

    WATER , SOAP AND OIL FORM A PERMANENT EMULSION

QUESTIONS:

    From your observation, which compounds can dissolve lipids?   As we have obvserved in the experiment, ethanol can dissolve oleic acid

    Do the oil and water mix? What can you conclude about the polarity of the oil if you know that water is polar?   Water and oil can't mix together because water can't dissolve lipids. Oil is a non-polar compound.
Why is liquid the olive oil lat room temperature?   Because it's an insaturated acid and has a low melting point.
Why does a lipid leave a translucent spot on paper?   Beacause it's a fatty acid.
Which type of milk contains more lipids? Why?   Full-cream milk contains more lipids than the others because is fattier.Did the oil and water mix when you added the soap?   Yes