Question

Predict whether water or carbon tetrachloride, \(\mathrm{CCl}_{4}\), is a better solvent for each of the following household substances. (a) grease (b) maple syrup (c) food color (d) gasoline

Short answer

Water dissolves maple syrup and food color; \( \mathrm{CCl}_4 \) dissolves grease and gasoline.

Step-by-step solution

Understanding Polarity of Solvents

Water is a polar molecule due to its bent shape and the difference in electronegativity between hydrogen and oxygen. Carbon tetrachloride, \( \mathrm{CCl}_4 \), is nonpolar because its symmetrical shape allows the dipole moments to cancel out. This difference in polarity is crucial for determining solubility of substances in these solvents.

Analyze Household Substance Polarity

For each substance, determine its approximate polarity. (a) Grease is nonpolar. (b) Maple syrup is a complex mixture primarily composed of sugar, which is polar. (c) Food color can vary but is often polar due to the ionic nature of dyes. (d) Gasoline is nonpolar due to its composition of hydrocarbons.

Apply Like Dissolves Like Principle

The principle 'like dissolves like' indicates that polar solvents best dissolve polar substances, and nonpolar solvents best dissolve nonpolar substances. We'll match each household substance to the solvent with similar polarity.

Match Solvents to Substances

(a) Grease, being nonpolar, is better dissolved by \( \mathrm{CCl}_4 \). (b) Maple syrup, which is polar, will dissolve better in water. (c) Food color, usually polar, is better dissolved in water. (d) Gasoline, being nonpolar, is more soluble in \( \mathrm{CCl}_4 \).

Conclusion

Water is a better solvent for maple syrup and food color due to their polar nature, while carbon tetrachloride is a better solvent for grease and gasoline because they are nonpolar.

Key concepts

Polarity of Water

Water is a polar molecule, which means it has a positive and a negative side. This happens because of its molecular shape and the difference in electronegativity between oxygen and hydrogen atoms. Oxygen is more electronegative than hydrogen, causing a partial negative charge near the oxygen atom and a partial positive charge near the hydrogen atoms. This dipole moment leads to water's ability to form hydrogen bonds, which play a significant role in its interactions with other molecules.
In practical terms, the polarity of water allows it to dissolve other polar substances easily, like salts and sugars. When water interacts with these substances, it overcomes the ionic and molecular attractions within them, effectively breaking them down into their components. This quality makes water an excellent solvent for many household substances that also exhibit polarity.

Nonpolar Solvents

Nonpolar solvents, such as carbon tetrachloride (\( \mathrm{CCl}_4 \)), do not have a distinct positive or negative end. This is primarily due to their symmetrical molecular structure, which allows any potential charges to be evenly distributed or canceled out, leading to an overall nonpolar characteristic. Because of this, nonpolar solvents generally do not mix well with polar substances. Instead, they are great for dissolving other nonpolar substances.
Common nonpolar solvents include not only carbon tetrachloride but also gasoline, oils, and fats. These substances do not dissolve well in water but are quite soluble in nonpolar solvents. This is because nonpolar solvents can interact more favorably with nonpolar molecules by dispersing the substances evenly throughout the solvent, given their similar intermolecular forces.

Like Dissolves Like Principle

The 'Like Dissolves Like' principle is a fundamental rule in chemistry that states polar solvents will best dissolve polar substances, while nonpolar solvents will best dissolve nonpolar substances. This principle arises because substances with similar polarity tend to interact more efficiently and achieve a stable mixture.
For instance, water, a polar solvent, readily dissolves polar substances such as sugar or salt due to similar polar interactions and the ability to form hydrogen bonds. On the other hand, nonpolar solvents like gasoline will dissolve nonpolar substances such as oils or grease because they can mix without disrupting each other's electron arrangements.
This principle helps predict and understand solubility behaviors in many practical applications, such as cleaning, cooking, and various industrial processes.

Household Substance Solubility

When we consider the solubility of common household substances, it's crucial to think about their polarity. Each substance's solubility can be predicted based on whether it's polar or nonpolar, and then matched to the appropriate solvent based on the 'Like Dissolves Like' principle.
For example:

• Grease, being nonpolar, does not dissolve in water but is soluble in nonpolar solvents like carbon tetrachloride.
• Maple syrup primarily consists of sugars, making it polar and thus best dissolved in water.
• Food colorings are often polar due to their ionic components, making them soluble in water.
• Gasoline, composed of hydrocarbons, is nonpolar and dissolves better in a solvent like carbon tetrachloride.

Understanding these interactions is key for practical tasks such as choosing the right cleaning solvents, cooking, or when setting up experiments, and also guides consumer product formulation.