Problem 98 - Chemistry: The Central Science

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?

Step-by-Step Solution

Answer

Using pure ethylene glycol instead of the recommended mixture of 30% ethylene glycol and 70% water results in reduced protection for the car due to its higher viscosity, lower heat capacity, and increased toxicity. The mixture provides an optimal balance between the antifreeze properties of ethylene glycol and the heat transfer properties of water, resulting in better performance and protection for the car's engine.

Step 1: Ethylene glycol (C2H6O2) is an organic compound used as an antifreeze agent in car radiators. Water (H2O) is a simple inorganic compound with high heat capacity and good heat transfer properties. Both compounds have their unique properties that affect their performance as a coolant in a radiator. #Step 2: Examine the properties of the mixture#

When ethylene glycol is mixed with water, it forms a solution with a lower freezing point than water alone. This is important for preventing the coolant from freezing in cold temperatures. At the same time, the mixture retains the excellent heat transferring properties of water, which helps to dissipate the heat generated by the car's engine. #Step 3: Understand the consequences of using pure ethylene glycol#

Step 2: Using pure ethylene glycol instead of the recommended mixture can have several negative consequences: 1. Ethylene glycol has a higher viscosity than water, meaning it is thicker and will not circulate as easily through the cooling system. This can impair heat transfer and increase the load on the engine's water pump. 2. The heat capacity of ethylene glycol is lower than that of water, meaning it doesn't absorb and transfer heat as efficiently. This can lead to the engine running hotter, which can cause damage or reduce performance. 3. Pure ethylene glycol is also more harmful to the environment and more toxic to humans and animals than a diluted solution. #Step 4: Explain why the recommended mixture is better#

The recommended mixture of 30% ethylene glycol and 70% water provides an optimal balance between the antifreeze properties of ethylene glycol and the heat transfer properties of water. The mixture has a lower freezing point, better heat transfer, and is environmentally and economically more viable than using pure ethylene glycol. The car owner's decision to use pure ethylene glycol reduced the protection for his car due to impaired heat transfer and increased system load, potentially causing damage to his engine.