# Pressure and molecules relationship

### Relationships among Pressure, Temperature, Volume, and Amount - Chemistry LibreTexts

Gas pressure in a closed container is the result of the gas molecules This relationship is called Boyle's law in honor of Robert Boyle who first. Avogadro's law is an experimental gas law relating the volume of a gas to the amount of substance of gas present. The law is a specific case of the ideal gas law. A modern statement is: Avogadro's law states that, "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules. . Boyle's law – Relationship between pressure and volume in a gas at. Early scientists explored the relationships among the pressure of a gas (P) and its temperature (T), volume (V), and amount (n) by holding two of the four.

Charles's Law Hot air rises, which is why hot-air balloons ascend through the atmosphere and why warm air collects near the ceiling and cooler air collects at ground level. Because of this behavior, heating registers are placed on or near the floor, and vents for air-conditioning are placed on or near the ceiling.

The fundamental reason for this behavior is that gases expand when they are heated.

### Relationships among Pressure, Temperature, Volume, and Amount

Because the same amount of substance now occupies a greater volume, hot air is less dense than cold air. The substance with the lower density—in this case hot air—rises through the substance with the higher density, the cooler air. A sample of gas cannot really have a volume of zero because any sample of matter must have some volume.

Note from part a in Figure 6. Similarly, as shown in part b in Figure 6.

### Pressure and the Gas Laws

The Relationship between Volume and Temperature. The temperature scale is given in both degrees Celsius and kelvins.

The significance of the invariant T intercept in plots of V versus T was recognized in by the British physicist William Thomson —later named Lord Kelvin. At constant pressure, the volume of a fixed amount of gas is directly proportional to its absolute temperature in kelvins. This relationship, illustrated in part b in Figure 6.

The Relationship between Amount and Volume: This relationship is called Boyle's law in honor of Robert Boyle who first observed that increased pressure lowered volume. As the volume a gas occupies decreases, the molecules of the gas are forced closer together, but their movement continues.

They have less distance to travel to impact the container walls so they strike more often, thus creating more pressure. This factor is the basis for the automobile piston.

It compacts the air-fuel mixture in the cylinder, thereby increasing pressure within the cylinder. Density of the Gas Increase the number of particles in a container, and the pressure of the system within the container increases.

More molecules mean more hits against the container walls. Increasing the number of particles means you have increased the density of the gas.

## 6.3: Relationships among Pressure, Temperature, Volume, and Amount

This third factor is part of the ideal gas law, which explains how these three factors -- temperature, volume and density -- interact with each other. If water were used instead of mercury, the height of the column equivalent to normal pressure would be The Gas Laws The example of the gas-filled balloon can also be used to explore the basic gas laws see also Appendix D, p.

In the following, lets assume that the balloon is tight, so that the amount or mass of air in it stays the same: With density being the ratio of mass per volume, the gas density of the balloon thus varies only with its volume when mass is held constant.

If we squeeze the balloon, we compress the air and two things will happen: Since density is mass over volume, and the mass stays constant, the rise in density means that the volume of the balloon decreases: