Difficulty: Medium

Average Score: 57%

Salt is applied to icy roadways because the salt

Rationale

Salt lowers the temperature at which ice melts.

When salt is applied to icy roadways, it disrupts the equilibrium of the ice and water, effectively lowering the freezing point of water. This process, known as freezing point depression, allows ice to melt at lower temperatures, making roads safer during cold weather conditions.

A (dissolves ice) YOUR ANSWER

Salt does not dissolve ice directly; rather, it alters the melting point of the ice. While salt does help in melting ice, its primary function is not to dissolve the ice but to prevent it from remaining solid at temperatures where it otherwise would. Thus, this option inaccurately describes the mechanism at work.

B (lowers the temperature at which ice melts) CORRECT

This statement accurately reflects the scientific principle of freezing point depression. By introducing salt to ice, the melting point of the ice decreases, allowing it to transition into liquid water even when temperatures are below the normal freezing point of pure water. This is the key reason for using salt on icy roads.

C (increases the temperature of the ice) YOUR ANSWER

Salt does not increase the temperature of the ice itself; instead, it facilitates melting by lowering the freezing point. This choice misrepresents the role of salt, as it does not provide thermal energy to elevate the temperature of the ice but rather changes the physical properties of the ice-water system.

D (decomposes water) YOUR ANSWER

Salt does not decompose water; it simply dissociates into its ions when dissolved. This option incorrectly suggests a chemical reaction that does not occur in this context. The interaction of salt with ice is a physical process, not a chemical decomposition of water.

Conclusion

The application of salt to icy roadways is primarily effective because it lowers the temperature at which ice melts, enhancing safety by preventing ice formation at temperatures that would otherwise support solid ice. This property is essential for winter road maintenance, as it helps keep roads clear and safe for travel by counteracting the effects of cold weather on ice formation.

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