Physics and Chemistry Lab

Our first experiment in lab session 1 was successfuly completed!

Objective:

To study, evaluate and compare the properties of several substances and relate them to their type of bonding (ionic, covalent or metallic).

Materials:

Substances A to D                                    Conductivity meter

Test tubes                                                 Distilled water

Spatula                                                      Acetone

Bunsen burner

Background:

Organic compound are any compound containing carbon atoms. The most commons are hydrogen, nitrogen and oxygen. Carbon atoms bond to another easily.

Acetone is a colorless, flammable liquid, CH3COCH3. Is completely soluble in water and organic solvents, acetone is itself an important solvent that it boils at 56.2 °C (133 °F). Acetone is used in the industry and chemistry.

Ionic Bonding: one atom completely removes one or more electrons from another element to form charged ions with full outer shells. This happens because the electro negativity of one element is higher than the other one. The difference between their electro negativity needs to be higher than 1.8. In the table we can observe that they have a high melting and boiling point, dissolve in water but not in organic solvent (acetone) and conduct electricity when dissolved in water but not when solid.

Covalent Bonding: atoms share electrons to complete their outer shell. This happens because the difference between their electro negativity is less than 1.8. We can observe in the table that it has low melting and boiling point, do not dissolve in water but do dissolve in organic solvent (acetone) and do not conduct electricity.

Method:

Repeat the procedure for each of the substances provided:

1.       Take ½ a spatula of the substance in a test tube. Describe the appearance of the substance.

2.       Gently heat it in the flame of the Bunsen burner and state if the approximate melting point. (Low, intermediate or high).

3.       Take ½ a spatula of the substance in another test tube.

4.       Add 10 mL water, stir it and state whether the substance is soluble in water or not.

5.       Repeat the steps 4 and 5 using acetone instead of water.

6.       Using the conductivity meter, state if the substance is a conductor in solid state.

7.       If it the substance is soluble in water, test whether the solution is a conductor or not.

The expected results of the experiment:

		Melting point	Solubility with water	Solubility with acetone	Conductivity in electricity
A	Iron (III) Sulfate heptahydrate	Medium	It is soluble	It is not soluble	Yes
B	Parafina	Low	It is not soluble	It is soluble	No
C	Starch	Low/Medium	It is soluble	It is not soluble	No
D	Iron	High	It is soluble	It is not soluble	Yes

The results of the experiment:

		Melting point	Solubility with water	Solubility with acetone	Conductivity in electricity
A	Iron (III) Sulfate heptahydrate	Medium	It is soluble	It is not soluble	No
B	Parafina	Low	It is not soluble	It is not soluble	No
C	Starch	High	It is soluble	It is soluble	No
D	Iron	High	It is soluble	It is soluble	No

TYPE OF BONDING:

Iron (III) Sulfate heptahydrate	Ionic
Parafina	Covalent
Starch	Ionic
Iron	Ionic

Iron (III) Sulfate heptahydrate, Starch and Iron have Ionic Bonding because one atom completely removes one or more electrons from another element to form charged ions with full outer shells. This happens because the electronegativety of one olement is higher than the other one. The difference between their electronegativety needs to be higher than 1,8. In the table we can observe that they have a high melting and boiling point, dissolve in water but not in organic solvent (acetone) and conduct electricity when dissolved in water but not when solid.

Parafina has Covalent Bonding because atoms share electrons to complete their outer shell. This happens because the difference between their electronegativety is less than 1,8. We can observe in the table that it has low melting and boiling point, do not dissolve in water but do dissolve in organic solvent (acetone) and do not conduct electricity.

Evaluation:

We think is a very interesting experiment because we worked with different elements and we could see it type of bonding.

We´ve chosen this element because they looked interesting for us it colour, when we touch it... we didn´t had any problem making the experiment but the method could specify more the quantity of grams we have to use in each element because ½ of the spatula we don´t know the exact measurement, a good solution is to measure it in a balance and we know the exact quantity we are using in the experiment.  Other problem in the method was that it tells us to state if the element is soluble in water and acetone or not, but they don´t tell us how we can know when is completely soluble or when we stop because the element is not going to dissolve.

We were very impressive with acetone because when you touch it you think is whet but when you see your hand is completely dry. Conductivity in electricity was very boring because nothing happens maybe because we didn´t know how to put correctly the conductivity meter, the best solution is to practice.

 We were very entertained proving all possible options. It was an easy and entertained experiment.

Conclusion

The expected results have been calculated based in the type of bonding and mostly in the elements (their shields, which affects the reactivity of a substance). As you can observe the expected results and the final results obtained from the experiment have not much difference, which tells us that our research and calculations have been more or less good. We can see that the expected melting point of starch is low/medium and when we made the experiment was high, this tells us that we would had probably don't made it well, for the next time we should make sure we get the correct substance and burn it in the correct way so that we don't get any differences between our results and the expected ones.
When we have made the dissolving in acetone part, the results where different. This could be because maybe the substance has been not dissolved correctly (for next time use another material/instrument or method for dissolve it), maybe the acetone wasn't pure and there was another substance (water for example) in the container and the substance has not dissolved correctly.
In the energy conductivity part we can observe also different results, so this is (explained above, in the evaluation) because we really didn't know how to know if it conducts energy (electricity) or not. We observed that the instruments we used for this weren't really good and didn't have a good state. For the next time we will make sure we have the correct material and ask more to the teacher for guide.
In general the experiment wasn't difficult, and any problems came up when making it, the problems with the results came after, but in general we are happy with the result of the whole experiment and report.

References:

Anne Marie Helmenstine, P. (2014). What Is an Ionic Bond?. [online] About. Available at: http://chemistry.about.com/od/chemistryglossary/a/ionicbonddef.htm [Accessed 20 Nov. 2014].

Anne Marie Helmenstine, P. (2014). What Is an Ionic Bond?. [online] About. Available at: http://chemistry.about.com/od/chemistryglossary/a/ionicbonddef.htm [Accessed 20 Nov. 2014].

Encyclopedia Britannica, (2014). acetone (CH3COCH3) (chemical compound). [online] Available at: http://global.britannica.com/EBchecked/topic/3270/acetone-CH3COCH3 [Accessed 20 Nov. 2014].

Encyclopedia Britannica, (2014). organic compound (chemical compound). [online] Available at: http://global.britannica.com/EBchecked/topic/431954/organic-compound [Accessed 20 Nov. 2014].