Final answer:
The measurement of specific gravities for radiator coolant and battery electrolyte is important for checking the freezing and boiling points of the coolant and the state of charge of the battery, respectively. A hydrometer is commonly used for these tests.
Step-by-step explanation:
The purpose of measuring the specific gravities of an automobile's radiator coolant and battery electrolyte is to assess their respective condition and performance characteristics. For radiator coolant, which typically consists of a mixture of ethylene glycol and water, the specific gravity helps in determining the freezing and boiling points of the coolant, crucial for optimal engine performance.
On the other hand, measuring the specific gravity of battery electrolyte, particularly in lead-acid batteries, provides an indication of the state of charge of the battery. A hydrometer is used for this purpose. When a lead-acid battery is charged, the specific gravity increases as sulfuric acid concentration increases while water electrolyzes into hydrogen and oxygen gases, especially if charged too vigorously.