Lab investigation: Comparing iconic molecular substances By:Baldeep Lally
Purpose: to compare the solubility in water and conductivity of ionic and molecular substances.
Background information:
An ELECTROLYTE is a material that contains free ions that can conduct electricity. We will be testing substances conduct electricity they are mixed in water using a conductivity tester. If the test solution conducts electricity, then the LED light will light up and we can conclude that the test solution is an electrolyte!
Hypothesis: My theory is that the conductivity of ionic substances won’t conduct very well because I just don’t think it will work.They are mostly powders and they will dissolve in the water. The light will only be dim if you put it in the water for the conductivity of ionic substance. I think that it will conduct very well with the molecular substances because molecular substances are liquids and so is water so they will conduct very well.
Station materials: watch glass, stir rod, conductivity tester, sample beaker and wooden splint, distilled water bottle, waste beaker, paper.
Ionic substances: salt (NaCL), potassium chloride(KCL), copper(lll), suffate (CuSO4)
Molecular substances: simple sugar (glucose), starch,oil.
Unknown substances: A and B
Procedure:
1.Make a small puddle of distilled water on the watch glass.
2.Place a small amount of the sample on a wooden splint and add it to the water.
3.Use the glass stirring rod to mix the sample with the water. Allow it time to dissolve.
$.Use the conductivity tester to find out if the water and sample mixture conducts electricity. Record your observations.
5.Empty the mixture into the waste beaker, Rinse and dry the watch glass, conductivity tester and stir rod.
Observations:
Table 1: solubility and conductivity of ionic and molecular substances.
Substance name
Type of substance
(Ionic or molecular)
Solubilty in water
(dissolved well/partially
Observation when testing for conductivity
(light off/light dissolved/did not dissolve. on steadily/ light flashing)
Conductivity (did not conduct/conducted well/conducted very well.

Salt(NaCL) Ionic Dissolved well Light on Did conduct very well
Potassium
Chloride (KCl)
Copper (ll)
Sulfate(CuSO4)
Starch
Simple sugar(glucose
Oil
Unknow A
Ionic
Ionic
Molecular
Molecular
Molecular
Molecular
Particially dissolved
Partically dissolved
Light on
Light on
Partically dissolved
Dissolved very well
Light on
Light on/flashing
Did not dissolve Light off
Dissolved well Light off
Conducted very well
Conducted well
Conducted well
Conducted well
Did not conduct
Did not conduct
Unknown B
Discussion:
Molecular Dissolved Light on Conducted well
1.
Discuss the solubility in water and conductivity of ionic substances when they are dissolved in water. Refer to your observations to support your discussion.
All the ionic substances dissolved in water. When they all dissolved in the water they all dissolved pretty well. And when I put the battery light on the water with the dissolved substance all the lights turned on and they all conducted well.
2.
Discuss the solubility in water and conductivity of molecular substances when they are dissolved in water. Refer to your observations to support your discussion.
Four of them dissolved partically well except for the oil one, because it didn’t conduct with the water and the light didn’t work. The oil stayed in one place.
Unknown A also didn’t conduct very well and the light was off aswell, it only dissolved. The rest conducted well.

3.
Based on your answer to questions 1 and 2,discuss how you could use these properties to determine whether an unknown compound Is ionic or molecular.
I can tell if there ionic or molecular by looking at my results in the observation sheet because all of the ionic ones dissolved well and only one of the molecular substance didn’t dissolve. All the ionic lights were on and only 3 out of 5 of the molecular lights were on. Both unknown A and B are molecular because they have the same traits as other molecular ones.
4.
Solve the mystery of the unknown compounds! Which is potassium bromide and which is table sugar (sucrose)? Explain your answer
Potassium bromide is unkown A because the light didn’t turn on and it really didn’t conduct very well with the water so the light didn’t turn on. Unknown B is table sugar because it dissolved, the light turned on and it conducted very well.
Conclusion: Summarize your results for the solubility in water and conductivity of ionic and molecular substances when they are dissolved in water. Discuss whether your hyphothesis was correct.
In conclusion my hypothesis was incorrect because two out of three substances conducted very well and one did not. All three of the lights were on very well, all of the substances dissolved in the water and for the molecular substances three out of five test experiments conducted very well. Also three out of five lights were on for the experiment and four out of 5 of the test experiments dissolved resulting in my observations. My experiment could have been better if I had waited for the substances to dissolve, then there would have been a different result as to what I had. When the battery was put into the water mixed with the substance I could have mixed the water more into the substance which would have created a different affect. In summary I think this project was conducted very well because
I followed all the steps and guidelines to do this experiment and my group was very cooperative to get the results we needed for this experiment.