MeltingPointLab

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Melting Point Lab

Introduction

• As you know from your knowledge of the Heating Curve, boiling point (BP) and melting point (MP) between two substance tend to have the same trends (i.e. if one's BP is higher than other, so too is its MP).
• The actual difference between substances for these two points is determined by the Intermolecular Forces (IMF) that each substance has (molar mass or molecular weight is also important sometimes).
• In this lab, you will first determine the type of IMF for both substances and then predict which substance melts first. Then you will actually melt each substance to experimentally determine the answer.

Procedures

1. This part is done at desks. In the calculation section, determine the type of compound the substance is using deltaEN to determine bond polar, molecular polarity, and therefore IMF. Finally, predict which one of the two will melts first.

2. This part is done in lab. Get a test tube rack and two small test tubes.

3. In one of the test tubes, add a small amount (approximately a tip of the spatula) of sodium chloride.

4. In the other other test tube, add a small amount (approximately a tip of the spatula) of dichlorobenzene.

5. Add approximately 100ml of water to a 250ml beaker and place on one of the heating elements.

6. Place both test tubes and a thermometer into the water.

7. Observe which one melts first and the approximate melting temperature.

8. DisposalTurn off the heating element and let everything cool. Then, the test tube with dichlorobenzene needs to be placed in the designated test tube rack in the middle of the lab area while everything else can be cleaned as usual. (liquid can be send down the drain & solids dumped in the trash.)

Data Table

• First Melting Point(degreeC):

• Substance that melted first:

Calculation

1. Chemical structure of sodium chloride:

2. State reason (i.e. determine) the type of compound sodium chloride (show deltaEN also):

3. State reason (ie. determine) the type of compound dichlorobenzene (C₆H₆Cl₂ (showing deltaEN also) Hint:determine all possible combination of atoms bond together and make educated guess of what type of IMF.

4. Predict which of the two substance will melt first:

Questions

• Did your laboratory observation support or disagree with your predicted results?