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 used in the investigation.
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.
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Answer
As the chain length increases, the strength of intermolecular forces also increases. This is because larger molecules have more surface area for interaction, resulting in stronger London dispersion forces. Therefore, with stronger intermolecular forces, a higher boiling point is observed. Their hypothesis accurately describes this relationship.
Step 8
Use the data in the table to write down a conclusion for the investigation.
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Answer
The data shows that as the chain length increases from C2H6 to C4H10, the boiling points also rise from -89°C to -0.5°C. This supports the conclusion that increasing chain length results in stronger intermolecular forces, leading to higher boiling points.
