Mengamati Polaritas Suatu Zat (English Version)

INVESTIGATING THE POLARITY OF A SUBSTANCE

A.            PRACTICAL PURPOSES

          As for the purposes of this practical are:

·         Investigating the polarity of substance

·         Knowing the differences between the polar compound and non-polar compound

·         Knowing the factors that influences polar or non-polar of material

B. THE THEORITICAL BASIS

          Molecules that have unevenly spreaded values are called polar molecules. As the result of the incompletely-spread of the distribution of electrons in a bond, an atom gets a positive value, it is drawn by Delta symbol, (d+)  and the other gets the negative value (d-).

At HCl molecule, as an example, the electronegative of Cl (3.2) is more than H atom (2.2). As the result of electron bonding take a longer time at the Chlorine atom than at the hydrogen. The result of Chlorine gets negative value and Hydrogen gets positive value. 

The creation of positive and negative values are separated by a position distance called Dipole.

The shape and Polarity of Molecules

When a molecule has more than one polar bond, the polarity of the molecule is built by add vector lines at the dipole bond. The conditions for a polar molecule :

1.    The molecule must be built of one or more polar bonds

2.    The molecule must be unsymmetrical

The rules for polar molecule :

-     The difference of electronegativities are high

-     There are pairs of free electrons

-     Dipole moment is not zero

-     The shape is unsymmetrical, so the positive charge doesn’t coincide with negative charge

-    Consist of metal and nonmetal atom.

       The characteristics of polar compound :

-    Can be dissolve in water and the others polar

-    Has positive and negative pole as the effect of unevenly electron distribution

-    Has free electron pairs or has electronegativity differences

The rules for non-polar molecule :

-          There is no/small difference of electronegativity

-          Dipole moment is zero

-          Doesn’t have pairs of free electrons

-          Has symmetrical shape

-          Consist of nonmetal and nonmetal atoms

The characteristics of non-polar compound

-          Can’t be dissolve in water and the others polar

-          Doesn’t have positive and negative pole

-          Doesn’t have free electron pairs

  The polar compound molecules can be influenced by electric and magnetic fields, so that a substance built by the polar molecules will bend when they get through the electric and magnetic fields. Meanwhile, the substance built by the non-polar compounds do not undergo the deviation when they get through the electric or magnetic fields.

         In this practical we’re using:

1.    H₂O (water)

H₂O is a formula of molecule, each molecule consist of one oxygen and two hydrogen molecules. O atom has atom number 8, the electron configuration is 2.6, while H = 1.

To be stabile, O atom follows the octet rules, while H duplet. Each O atom needs 2 electron for stabile, while H only needs one.
The bond that built between O and H is a polar covalent bond. Because of the electronegativity of O is bigger than H, so the electron pairs are almost nearer with O.

By the event, H become more positive and O becomes more negative, but it doesn’t mean that they become ions because they use the electrons together. The electric charge that formed only partial, then named with pole. Water molecule has south and north pole, then it is stated polar.

2.    Cooking oil (C₁₄H₂₄)

Because of Carbon element and Oxygen can’t be attract by the hydrogen and oxygen that there in the water. It is happened because some of that elements have the same electronegativity and some of that electrons are almost won’t take a bond with others and so do with compound. So, it is non polar, as the theory of “like dissolve like”, a substance can be dissolve in a dissolver if have the same polarity. For that, cooking oil is non-polar.

C.TOOLS AND MATERIALS

TOOLS NEEDED

NO.	TOOLS	TOTAL NEEDED
1.	Bar magnet	1
2.	Used plastic bottle	1
3.	Small nail	1 pack
4.	Pail	1

MATERIALS NEEDED

NO.	MATERIALS	TOTAL NEEDED
1.	Water	1 glass
2.	Vegetable oil	1 glass

D.            WORKING PROCEDURES

WORKING PROCEDURES WITH USING WATER, ALCHOHOL, AND VEGETABLE OIL

NO.	PROCEDURE	PICTURE
1.	Make a hole in the bottom of plastic bottle using a small nail
2.	Hold the bottle above a pail and fill it with water
3.	Have your friend draw the bar magnet closer to the water which come out from hole of the bottle and observe the flowing condition
4.	Make a hole in the bottom of plastic bottle using a small nail
5.	Make a hole in the bottom of plastic bottle using a small nail
6.	Hold the bottle above a pail and fill it with vegetable oil
7.	Have your friend draw the bar magnet closer to the water which come out from hole of the bottle and observe the flowing condition

E. EXPLAINATION

A. TABLE OF OBSERVATION RESULT

NO.	MATERIAL	BEFORE CLOSED TO MAGNET	AFTER CLOSED TO MAGNET
1.	Water	Straight	Undeviate
2.	Vegetable oil	Straight	Undeviate

B.  EXPLAINATION

·         For the water, in the theory said that water would be deviate because water is polar compound. But, in our experiment, the water is not deviate by the magnet, it could be influenced by the small attraction force of the magnet.

·         For the vegetable oil, as the theory the vegetable oil should be no deviate, and we got the same things in our experiment.

F.  CONCLUSION

·         For  water, the theory and our experiment is not worked on the same way. The theory says that it would be deviate by the magnet, but we got it no deviate at all in our experiment. So, according to us, the measuring of attraction force of the magnet is not big enough to deviates the stream of the water from the glass.

·         For the vegetable oil, our theory and our experiment are worked on the same way that it got no deviate from the magnet.

G.QUESTIONS AND ANSWERS

1)   How is the flow condition for each substance when the bar magnet is drawn closer to the flow ?

For the water, itis deviate when they are close to the magnet bar.

For the vegetable oil, the substance is not deviate at all.

2)   Which substance are classified into the ones built of polar and non-polar molecules ?

Polar : water

Non-polar : vegetable oil.

H.Bibliography

·        www.kurniansyah-rizki.blogspot.com/2011/03/senyawa-polar-dan-non-polar.html

·        www.smartsains.blogspot.com/2008/09/perbedaan-senyawa-polar-dengan-non.html

·        www.ichachot.blogspot.com/2012/07/alkohol-senyawa-polar.html

·        id.answer.yahoo.com/question/index?qid=20101202135441AANd2i8