Air density refers to the density of air per unit volume of air at a certain temperature and pressure. Under standard conditions (0 ° C, 1 standard atmosphere (1atm)), the air density is about 1.29Kg / m³.
Air density = 1.293 * (actual pressure / standard physics
[Purpose and requirements]
Experiment to learn how to determine the density of air.
[Instruments and Equipment]
Plastic or glass containers with valves, pumps, beakers, sinks, measuring cylinders, balances.
experimental method
1. Open the container valve and inflate the container with a pump. Stop pumping to a certain extent and close the valve. Weigh the container with a balance (Figure 1.24-1).
The formula for calculating the air density is
= (m 1 -m 0 ) / V
In the formula: m 1 is the total mass of the density bottle and air, V is the corresponding volume, and m 0 is the mass of the density bottle.
There is always water vapor in the atmosphere, and the water vapor pressure can reach 1 × 10 3 Pa, and it varies greatly with time and place. Let the partial pressure of water vapor in the air sample be p w , and treat both air and water vapor as ideal gases. When the thermodynamic temperature is T, theoretically derived, the density of dry air in the standard state (P 0 , T 0 ) is
In the formula: p 0 = 1.01325 × 10 5 Pa, T 0 = 273.15K, p is the air pressure measured by the barometer, and is the inverse of 273.15.
The experimental instrument is shown in the figure
1) Measure the volume of the density bottle. Use a vernier caliper to measure the outer diameter D, length L, upper base plate thickness 1 , lower base plate thickness 2 , and side wall thickness 0 of the density bottle to calculate the volume V of the density bottle.
2) Turn on the density bottle switch, put the total weight m 1 of air and density bottle on the electronic physical balance, and then lay it on the table. The bottle mouth is connected to the vacuum rubber tube.
3) When the vacuum valve is opened and the vacuum gauge reads close to -0.1MPa, the air in the bottle has been evacuated. 4) Put the density bottle on the electronic physical balance and weigh its mass m 0 to calculate the ambient air density. 5) Read out the laboratory temperature t and the value t of the wet thermometer from the wet and dry bubble mercury thermometers, and calculate based on the data table of the relative humidity of the air and the temperature difference between the dry and wet bubble thermometers and the data table of the relationship between the saturated vapor pressure and temperature of water The partial pressure p w of water vapor.
6) Measure ambient atmospheric pressure p using a Fortin mercury barometer. 7) Substitute each quantity into the calculation formula, calculate the density of air in the standard state, and compare it with the given standard value. [1]
