Question

A car owner who knows no chemistry has to put antifreeze in his car's radiator. The instructions recommend a mixture of \(30 \%\) ethylene glycol and \(70 \%\) water. Thinking he will improve his protection he uses pure ethylene glycol. He is saddened to find that the solution does not provide as much protection as he hoped. Why not?

Short answer

The car owner did not achieve the desired protection because pure ethylene glycol has a higher freezing point and lower boiling point compared to the recommended mixture of 30% ethylene glycol and 70% water. The recommended mixture provides better protection against freezing and overheating, ensuring that the radiator functions properly in extreme conditions, where pure ethylene glycol may fail.

Step-by-step solution

Understanding antifreeze mixtures

Antifreeze is a mixture of a chemical compound, usually ethylene glycol, and water. This mixture is used in car radiators to prevent the coolant from freezing in cold temperatures and from overheating in hot temperatures. The recommended mixture is 30% ethylene glycol and 70% water.

Pure ethylene glycol properties

Pure ethylene glycol (100% concentration) has a higher freezing point and lower boiling point compared to its mixture with water. This means that pure ethylene glycol becomes less effective at extreme temperatures.

Mixture of ethylene glycol and water properties

When ethylene glycol is mixed with water in the recommended ratio (30% ethylene glycol and 70% water), the mixture has a significantly lower freezing point and higher boiling point compared to pure ethylene glycol.

Effectiveness of the recommended mixture

The reason the recommended mixture of 30% ethylene glycol and 70% water is more effective than pure ethylene glycol is that it provides better protection against freezing and overheating. The mixture can withstand a wider range of temperatures, ensuring that the radiator functions properly in extreme conditions, where pure ethylene glycol may fail.

Conclusion

In conclusion, using the recommended antifreeze mixture of 30% ethylene glycol and 70% water provides more effective protection against freezing and overheating compared to using pure ethylene glycol. The car owner's mistake was in not following the recommended instructions, which led to reduced protection for his car's radiator.