Problem 1 - Campbell Biology

Question

Which of the following is a hydrophobic material? (A) paper (C) wax (B) table salt (D) sugar

Step-by-Step Solution

Answer

Wax is the hydrophobic material.

Step 1: Identify Key Term: Hydrophobic

First, it's important to understand what 'hydrophobic' means. A hydrophobic material is one that repels water or does not mix with water.

Step 2: Evaluate Paper

Consider if paper is hydrophobic. Paper absorbs water readily, making it hydrophilic, not hydrophobic.

Step 3: Evaluate Table Salt

Consider if table salt is hydrophobic. Table salt dissolves easily in water, which means it is hydrophilic, not hydrophobic.

Step 4: Evaluate Sugar

Consider if sugar is hydrophobic. Sugar dissolves in water, indicating that it is hydrophilic, not hydrophobic.

Step 5: Evaluate Wax

Consider if wax is hydrophobic. Wax does not mix with water and tends to repel it, which makes it hydrophobic.

Step 6: Conclusion

Compare the evaluations: wax is the only material on the list that is hydrophobic.

Key Concepts

Hydrophilic vs. Hydrophobic

Understanding the difference between hydrophilic and hydrophobic materials is crucial. Hydrophilic materials attract water molecules and usually dissolve or absorb water. Examples include paper, sugar, and table salt. Hydrophobic materials, on the other hand, repel water and do not mix with it. Wax is a good example of a hydrophobic material.

Material Properties

Material properties determine whether a substance is hydrophilic or hydrophobic. Papers are made from cellulose fibers which naturally absorb water. Salt (NaCl) dissolves in water due to ionic bonds, as water molecules surround the ions and pull them apart. Sugar is also water-soluble due to its molecular structure, which forms hydrogen bonds with water. Wax, in contrast, is composed of long hydrocarbon chains that repel water molecules, making it hydrophobic.

Water Solubility

Water solubility is a key factor in classifying materials as hydrophilic or hydrophobic. Hydrophilic substances dissolve or mix well with water. This is because the molecules form favorable interactions with water, such as hydrogen bonding. Hydrophobic substances do not dissolve in water. Their molecular structure typically prevents the formation of such interactions. Hence, they repel water and remain separate. For instance, wax's hydrophobic nature makes it repel water and not mix with it, while substances like sugar and salt dissolve due to their hydrophilic properties.