Final answer:
The units of pressure and force are referred to as derived units because they depend on other fundamental units and mathematical operations. The SI system of units is preferred over the MKS system because it provides a standardized and globally recognized system for scientific measurements. The volume of gas is difficult to measure due to its dependence on various factors and the physical properties of the gas.
Step-by-step explanation:
The units of pressure are derived from the units used to measure force and area. The SI unit for pressure, derived from the SI units for force (newtons) and area (square meters), is the newton per square meter (N/m²), which is called the Pascal (Pa). This makes pressure and force derived units because they are dependent on other fundamental units and mathematical operations.
Gases exert pressure, which is force per unit area. The pressure of a gas may be expressed in the SI unit of pascal or kilopascal, as well as in many other units including torr, atmosphere, and bar. Atmospheric pressure is measured using a barometer; other gas pressures can be measured using one of several types of manometers.
In conclusion, the SI system of units is better than the MKS system because it provides a standardized and globally recognized system for scientific measurements. It allows for easier communication and comparison of data across different studies and countries.
The volume of gas is difficult to measure because it can change with temperature, pressure, and the physical properties of the gas. Additionally, gases are easily compressed and can expand to fill their container. To measure gas volume accurately, specialized equipment such as gas syringes or burettes are used.