Experiment 2: Melting Points and Types of Bonds Materials: 5 Aluminum cupcake wr

Question

Experiment 2: Melting Points and Types of Bonds

Materials:

5 Aluminum cupcake wrappers
Permanent marker
Ring stand
Ring for ring stand
Square of foil
Sterno®
Matches
Stopwatch
Ruler
1 Pair of gloves

1 pinch of the following chemicals:

- Sucrose, C12H22O11
- Sodium chloride, NaCl
- Stearic acid, C18H36O2
- Corn starch, C6H10O5
- Sodium bicarbonate, NaHCO3

*Kitchen tongs
*Paper towels

*You must provide

Procedure

Label the five cupcake wrappers from 1 - 5. Each wrapper will hold one of the following chemicals: 1 = Sucrose, 2 = Sodium chloride, 3 = Stearic acid, 4 = Corn starch, 5 = Sodium bicarbonate.

Put on a pair of gloves and goggles, and place a small pinch of each chemical into the corresponding wrapper. Be sure to wipe off your gloves on a paper towel between chemical samples to avoid crosscontamination.

Predict which compound you believe will melt first and record this in Table 3.

Fasten the ring on the ring stand, and cover the ring with foil to create a platform (rather than an open ring) to set the cupcake wrappers on. The ring should be positioned approximately 3 inches above the surface you are working on.

Place the first cupcake wrapper on the ring.

Remove the inner ring from the Sterno® and use matches to carefully light the igniter fiber. Place the Sterno® under the cupcake wrapper. Make sure that no flammable items (alcohol, paper, etc.) are located near the Sterno®. Flames should always be given extra attention. Please be very careful when working with flames, and never grab hot lab-ware with bare skin exposed.

Start a stopwatch, and record how long it takes the chemical to melt in Table 3. If a sample has not melted after two minutes, record it as “did not melt”.

Note: The average temperature for a candle flame is approximately 1,000 °C. However, the exact temperature of the heat when it reaches your chemical will vary by altitude, room temperature, wick length, etc.

Use kitchen tongs to put the lid back on the Sterno® to extinguish the flame. Allow the cupcake wrapper to cool down before handling.

Repeat Steps 5 - 8 with the remaining chemicals.

Based on the melting point order and information from the introduction, determine what type of bond the compound uses (ionic or covalent) and record your answers in Table 3.

Table 3: Melting Point Data

Prediction

Compound Name

Time the Compound Took to Melt

Melting Order (or, indicate if the compound did not melt)

Type of Bond

1st =

2nd =

3rd =

4th =

5th =

Materials:

5 Aluminum cupcake wrappers
Permanent marker
Ring stand
Ring for ring stand
Square of foil
Sterno®
Matches
Stopwatch
Ruler
1 Pair of gloves

1 pinch of the following chemicals:

- Sucrose, C12H22O11
- Sodium chloride, NaCl
- Stearic acid, C18H36O2
- Corn starch, C6H10O5
- Sodium bicarbonate, NaHCO3

*Kitchen tongs
*Paper towels

*You must provide

Explanation / Answer

I cannot tell you the time to compound the melt, but I can tell you which one could melt first and which one not.

The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard pressure. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point.

So,the ionic salts (as NaCl) usually have higher melting points (Above 800 °C), so this would be the last one to melt (or maybe did not melt), on the otherhand NaHCO3 will melt first because it has a low Ka, and has a reported melting point of 50 °C.

These two salts have an ionic bond.

The next on the list with a reported melting point of 70 °C, is the stearic acid (a fatty acid). These acids are very non polar solvents, so, they can actually melt faster. The third one to melt would be the corn stach with a melting point of 182 °C and finally, the sucrose (186 °C).

All of these bonds are covalent (Like the majority of organic compounds)

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