group of students performed a melting point experiment to study the physical properties of ionic and covalent solids. The data collected are shown in the table. Solid Sample Melting Point (oC) Time Elapsed (min) Table Sugar (sucrose) 186 18 Table Salt (sodium chloride) 500 (not observed) 30 Paraffin Wax 37 4 Vegetable Lard 50 >5 Using the information contained in the table, what is the BEST explanation for the results? A The melting point of sodium chloride was not observed because ionic solids do not melt, whereas sugar, wax, and lard melted because they are softer than salt. B The melting points of covalently bonded solids tend to be lower than ionic solids. The melting point of sucrose was greater than the wax or the lard because sucrose has stronger bonds than wax or lard. C The melting point of sodium chloride was not observed because ionic solids are composed of positive and negative ions that do not melt; whereas, the sucrose, wax, and lard are covalently bonded compounds that do not contain ions. D The melting point of sodium chloride was not observed because the students did not wait long enough for the salt to absorb enough heat energy to melt. The sugar, wax, and lard all require less heat to melt so they melted during the experiment.
A group of students performed a melting point experiment to study the physical properties of ionic and covalent solids. The data collected are shown in the table.
|
Solid Sample |
Melting Point (oC) |
Time Elapsed (min) |
|
Table Sugar (sucrose) |
186 |
18 |
|
Table Salt (sodium chloride) |
500 (not observed) |
30 |
|
Paraffin Wax |
37 |
4 |
|
Vegetable Lard |
50 |
>5 |
Using the information contained in the table, what is the BEST explanation for the results?
A
The melting point of sodium chloride was not observed because ionic solids do not melt, whereas sugar, wax, and lard melted because they are softer than salt.
B
The melting points of covalently bonded solids tend to be lower than ionic solids. The melting point of sucrose was greater than the wax or the lard because sucrose has stronger bonds than wax or lard.
C
The melting point of sodium chloride was not observed because ionic solids are composed of positive and negative ions that do not melt; whereas, the sucrose, wax, and lard are covalently bonded compounds that do not contain ions.
D
The melting point of sodium chloride was not observed because the students did not wait long enough for the salt to absorb enough heat energy to melt. The sugar, wax, and lard all require less heat to melt so they melted during the experiment.
Explanation
NaCl is ionic compound and hence has very high melting point (~801 oC). The sugar has covalent compound and will have melting point lower than ionic compound. Wax and vegetable are amorphous compound and will have very melting point.
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