Which instrument is used to measure the pressure of gases and liquids?

The manometer is specifically designed to measure the pressure of gases and liquids. This instrument operates by balancing a column of liquid against the pressure being measured, providing an accurate reading of the pressure in various systems. It is commonly used in various fields such as chemistry and engineering to monitor gas and liquid pressures in different environments, making it essential for both laboratory and industrial applications.

While the other instruments listed have distinct functions, they do not measure pressure in the same manner. A hygrometer is used to measure humidity in the air, while a barometer measures atmospheric pressure, specifically the weight of air above a given point. A thermometer, on the other hand, measures temperature but does not provide any information regarding pressure. This distinction underscores why the manometer is the correct answer for measuring pressures in gases and liquids.