A group of learners conducted an investigation in order to find the relationship between the boiling points and the chain lengths of three alkanes - NSC Technical Sciences - Question 3 - 2022 - Paper 2
Question 3
A group of learners conducted an investigation in order to find the relationship between the boiling points and the chain lengths of three alkanes. The results of th... show full transcript
Worked Solution & Example Answer:A group of learners conducted an investigation in order to find the relationship between the boiling points and the chain lengths of three alkanes - NSC Technical Sciences - Question 3 - 2022 - Paper 2
Step 1
Investigative question
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Answer
What is the relationship between chain length/molecular mass/surface area and boiling point in alkanes?
Step 2
Independent variable
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Answer
Chain length/molecular mass/surface area of the alkanes.
Step 3
Dependent variable
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Answer
Boiling point of the alkanes.
Step 4
Controlled variable
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Answer
The type of alkane being tested, the environmental conditions, and measurement consistency.
Step 5
Write down the NAME of the intermolecular forces referred to in the hypothesis
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Answer
London dispersion forces.
Step 6
Is their hypothesis CORRECT or INCORRECT? Write down only CORRECT or INCORRECT.
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Answer
CORRECT.
Step 7
Explain the answer to QUESTION 3.2.2. Refer to the chain length, the strength of the intermolecular forces and boiling point.
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Answer
The hypothesis is correct because as the chain length increases, the surface area also increases, leading to stronger London dispersion forces. Stronger intermolecular forces result in higher boiling points, which supports the statement made in the hypothesis.
Step 8
Use the data in the table to write down a conclusion for the investigation.
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Answer
As observed in the data, the boiling points increase with increasing chain length: C₂H₆ has the lowest boiling point at -89°C, followed by C₃H₈ at -42°C, and C₄H₁₀ at -0.5°C. This trend confirms that longer chains lead to stronger intermolecular forces and higher boiling points.
