you need
  • thermometer, pressure gauge, sealed cylinder scales
Calculate the internal energy of the gas can be reliably only when its state is close to ideal.Then we can neglect the potential energy of the interaction of its molecules.Practically all gases at room temperature, have properties similar to those of an ideal gas.
First, determine the chemical formula of the gas, the internal energy is calculated.Measure the mass of the gas using the weights in grams.To do this, first weigh the empty bottle and then filled with a gas, the difference of their mass will be equal to the mass of the gas.Use the periodic table to find it molar weight in grams per mole.
with a thermometer to measure the t
emperature of the gas.If the scale of the thermometer is scaled in degrees Celsius, it is in Kelvin.To do this, add to the resulting value of 273.
Calculate the internal energy of the gas.To do this, divide the mass of the gas in the molar mass.The obtained result to multiply the value of the temperature and the number of 8.31 (the universal gas constant), then multiply by the number of degrees of freedom and gas molecules divide by 2 (U = m / M • (R • T) • i / 2).Number of degrees of freedom for a monatomic gas is 3 to 5 molecules of diatomic and polyatomic molecules 6. This is due to the motion of each of the molecules.
If you can not measure the temperature of the gas, but also known for its volume and pressure, calculate its inner energy through these values.To do this, measure the weight of the gas, its molar mass and find the chemical formula.Express the volume in cubic meters, and the pressure in Pascals.Calculate the internal energy of the gas, multiplying the number of degrees of freedom of a gas molecule, its mass, pressure, volume, and divide the result by 2 and molar mass of the gas (U = m • i • P • V / (2 • M)).
In general, the change in internal energy of the gas is equal to the difference it has received heat from the outside and work performed ΔU = QA.