Relationships among Pressure, Temperature, Volume, and Amount - Chemistry LibreTexts
To understand the relationships among pressure, temperature, volume, and the two of the four variables constant (amount and temperature, for example). The gas laws deal with how gases behave with respect to pressure, volume, The Gas Laws: Pressure Volume Temperature Relationships EXAMPLE 1. Relationship between density, pressure, and What happens to pressure if temperature increases? – Increases. P ~ T Numerical example. • What is the.
Boyle's Law As the pressure on a gas increases, the volume of the gas decreases because the gas particles are forced closer together. Conversely, as the pressure on a gas decreases, the gas volume increases because the gas particles can now move farther apart.
Weather balloons get larger as they rise through the atmosphere to regions of lower pressure because the volume of the gas has increased; that is, the atmospheric gas exerts less pressure on the surface of the balloon, so the interior gas expands until the internal and external pressures are equal.
Temperature and gas calculations
The Irish chemist Robert Boyle — carried out some of the earliest experiments that determined the quantitative relationship between the pressure and the volume of a gas. Boyle used a J-shaped tube partially filled with mercury, as shown in Figure 6. In these experiments, a small amount of a gas or air is trapped above the mercury column, and its volume is measured at atmospheric pressure and constant temperature. More mercury is then poured into the open arm to increase the pressure on the gas sample.
The pressure on the gas is atmospheric pressure plus the difference in the heights of the mercury columns, and the resulting volume is measured.
- Quick derivation
This process is repeated until either there is no more room in the open arm or the volume of the gas is too small to be measured accurately. This relationship between the two quantities is described as follows: Dividing both sides of Equation 6. The numerical value of the constant depends on the amount of gas used in the experiment and on the temperature at which the experiments are carried out. At constant temperature, the volume of a fixed amount of a gas is inversely proportional to its pressure.
6.3: Relationships among Pressure, Temperature, Volume, and Amount
Boyle used non-SI units to measure the volume in. For laboratory work the atmosphere is very large. A more convient unit is the torr.
A torr is the same unit as the mmHg millimeter of mercury. It is the pressure that is needed to raise a tube of mercury 1 millimeter. The Pressure-Volume Law Boyle's law or the pressure-volume law states that the volume of a given amount of gas held at constant temperature varies inversely with the applied pressure when the temperature and mass are constant.
Relationships among Pressure, Temperature, Volume, and Amount
Another way to describing it is saying that their products are constant. When volume goes up, pressure goes down. From the equation above, this can be derived: This equation states that the product of the initial volume and pressure is equal to the product of the volume and pressure after a change in one of them under constant temperature.
For example, if the initial volume was mL at a pressure of torr, when the volume is compressed to mL, what is the pressure? Plug in the values: The Temperature-Volume Law This law states that the volume of a given amount of gas held at constant pressure is directly proportional to the Kelvin temperature. V Same as before, a constant can be put in: Outside of the can the volume is not held constant.
Thus the contents are free to expand when they move from the high pressure in the can to the low pressure outside of the can. Expansional cooling causes the contents coming out of the can to cool.
This effect can be noticed in spray-on deodorants. In the second example, a compressor is shown. This is used in appliances such as refrigerators.
The refrigerant air is pressurized into the compressor meaning the pressure increases as more air is squeezed into the same volume. This causes a temperature increase.