# Qualitative relationship between pressure and volume

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

As Kelvin increase, energy increases. As the energy of something increases, its particles will move faster and with more force. This will mean. It is these collisions between the particles of the gas and the walls of the container it The relationship of a gas with pressure and volume was developed by the. describe the qualitative relationship between pressure and Kelvin so does the energy, because the particles move faster and with more force. use the relationship between the pressure and volume of a fixed.

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. Boyle used non-SI units to measure the volume in.

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

Hg rather than mmHg. Because PV is a constant, decreasing the pressure by a factor of two results in a twofold increase in volume and vice versa. The Relationship between Temperature and Volume: 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.

## Temperature and gas calculations

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.

**Animation : Relationship of Pressure with Volume and Temperature**

Similarly, as shown in part b in Figure 6. 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: If you increase T in the expression and keep everything else n, R and V the same, p will also increase.

Thus, the formula qualitatively agrees with what you know to be true. If it did not, you would know immediately that the formula was incorrect.

### BBC Bitesize - GCSE Physics (Single Science) - Temperature and gas calculations - Revision 3

Now, you can go on and check the rest of the variables: The quantitative check involves some mathematics and can be a little trickier, but like any skill, all that is needed is some practice. Here, we are asking a more detailed question than in Step 3, namely, if I change one variable by some factor, by what factor will the result change?

Again, it is very important to keep all the other variables the same. This is a quantitative question, because now we need a numerical answer. For example, if I double the temperature i. This is not a question that you can answer, right off. So, first, we must learn how to extract an answer from the formula.

Second, we must do an experiment to find out whether this answer is correct. How one quantity pressure changes with another temperature is called a dependence, in other words, it answers the question: Calculating Quantitative Dependencies Again, consider the pressure of a gas in a container: Notice that you might not understand some of these terms, like the number of moles of gas or the gas constant.

However, the great thing about dependencies is that you do not need to know or understand everything to answer some useful questions. This is really an important goal of physics, to make interesting observations or predictions even in the face of incomplete understanding.