3.1 Define the term melting point - NSC Physical Sciences - Question 3 - 2021 - Paper 2
Question 3
3.1 Define the term melting point.
3.2 Write down the general conclusion that can be made about the melting points of straight-chain alkanes.
3.3 Name the type of ... show full transcript
Worked Solution & Example Answer:3.1 Define the term melting point - NSC Physical Sciences - Question 3 - 2021 - Paper 2
Step 1
Define the term melting point.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The melting point is defined as the temperature at which a solid becomes a liquid, indicating the point of equilibrium between the solid and liquid phases of a substance.
Step 2
Write down the general conclusion that can be made about the melting points of straight-chain alkanes.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
As the carbon chain length of straight-chain alkanes increases, the melting points tend to increase. This is due to the greater surface area and stronger Van der Waals forces that result from longer carbon chains.
Step 3
Name the type of Van der Waals forces between molecules of octane.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The type of Van der Waals forces between molecules of octane is London dispersion forces.
Step 4
Write down the predominant phase of the following alkanes at -100 °C.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
3.4.1 Pentane: Solid
3.4.2 Octane: Solid
Step 5
Is the molecular mass of hexane GREATER THAN, LESS THAN or EQUAL to that of 2,2-dimethylbutane?
97%
117 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The molecular mass of hexane is LESS THAN that of 2,2-dimethylbutane.
Step 6
Is the boiling point of 2,2-dimethylbutane HIGHER THAN or EQUAL TO that of hexane?
97%
121 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The boiling point of 2,2-dimethylbutane is LOWER THAN that of hexane.
Step 7
Fully explain the answer to QUESTION 3.5.2.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
2,2-dimethylbutane is more branched compared to hexane, leading to a smaller surface area and weaker intermolecular forces. As a result, less energy is required to overcome these forces, resulting in a lower boiling point.
