Question

Shape, melting point & solubility (2.5 pts) When melting or boiling a substance (both of which are physical changes), which kinds of attractions may be broken? Circle all that apply. hydrogen bonding covalent bonds dipole-dipole London forces vs. If I told you that only one of these molecules is a solid at room temperature, which one is that more likely to be? How can you tell from the structure? Circle the hydrophilic portion of the molecules above and put a box around the hydrophobic parts. Are these molecules likely to dissolve in water? How have you decided?

Answer 1

During melting and boiling ,the intermolecular forces of attraction will be broken .
they are :: Hydrogen bonding, dipole-dipole, London force

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the first one is unsaturated fatty acid.the 2nd one is saturated fatty acid
saturated fatty acids are usually in solid state at room temperature
hence 2nd one is solid at room temperature
CH3-(CH2)15-COOH -is solid.

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Polar end of the fatty acid will be attracted to water [since water is polar] .that part
is called hydrophilic end . In above 2 structures -COOH end is polar due to
electronegativity difference between O and H atoms. So that end is called
hydhrophilic . COOH group is hydroPhilic

Hydrocarbon part is hydrophobic. Because that part is non polar

These compounds have long hydrophobic part present in the structure. Hence these
are insoluble in water.