# Ideal Gas Law - Real Life Question?

• I
• Monday
In summary, the conversation discusses the application of the ideal gas law to the inflation of bike tires and scuba tanks. The law suggests that if pressure is increased while volume remains constant, the temperature of the gas will also increase. However, in practical applications, the temperature increase is not significant due to the mixing and cooling of hot air with the existing cooler air inside the tire or tank.
Monday
Hi Guys and Gals,

As I was pumping up a flat bike tyre, a weird thought occurred to me about the application of the ideal gas law.

Once the tyre essentially finds its physical dimension limitations (i.e. is shaped like a bike tyre and no longer changing shapes) and starts putting in reasonable volumes of air, let's say up to 60-70lbs/in^2, why doesn't the tube get stupidly hot - in essence, the pressure is going from say 1 atmosphere to 3-5 atmospheres of pressure, but the physical space is not changing. By extension, you could equally apply the same concept to scuba tanks that go even way higher in pressure than a bike tube (and there definitely isn't any change to vessel shape)!

The ideal gas law would suggest holding volume constant, by changing pressure, the only other variable is temperature. So yeah, the valve on the tube gets a little bit warm, but its hardly finger frying, 3rd degree burn territory.

Any thoughts would be appreciated!

Cheers,
M

PV/T is constant law applies to a given amount of gas with same density. Not changing mass or density of gas. Think it as PV = nRT and think it over if P is increasing with V and T almost remaining constant then what is changing in the same proportion!?

Ok, so in a closed system (lets assume some sort of syringe device that is 100% closed - obviously theoretical only), if the volume of air is halved, but the pressure is doubled (so no change on T) is what youre getting at? Hence why I wouldn't see any temperature changes? 0.5 x V, but 2 x P = No change to the numerator?

For a practical application, can I ask then how would one dramatically increase T then simply by changing P or V, or is there no real ability to effect this in the 'real world'?

The temperature of the mass of air entering the tire at the end of each stroke of the pump is elevated, as you suspect. The higher the pumping pressure, the hotter the air. I have had the bottom section of a tire pump get nearly burning hot when quickly pumping a high pressure road bike tire (125 psi), so it can be significant. But that small amount of hot air then enters the tube and mixes with the larger body of colder air already inside the tire. Over the time it takes to pump up the tire the air inside the tube has had time to mix and cool. This is why the tire isn't anywhere near as hot as the bottom of the pump can get.

billy_joule

## 1. What is the Ideal Gas Law?

The Ideal Gas Law is a mathematical equation that describes the relationship between the pressure, volume, temperature, and number of moles of an ideal gas. It is represented by the formula PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature.

## 2. How is the Ideal Gas Law used in real life?

The Ideal Gas Law is used in various real-life applications, including weather forecasting, gas laws experiments, and the production of industrial gases. It is also used in the design of gas storage tanks and pipelines, as well as in the study of the behavior of gases in different environments.

## 3. What are the limitations of the Ideal Gas Law?

The Ideal Gas Law assumes that the gas particles have no volume and do not interact with each other, which is not true for real gases. It also assumes that the gas is at a low pressure and high temperature, and that the gas molecules are in constant motion. These assumptions may not hold true in all real-life situations, and hence, the Ideal Gas Law may not accurately predict the behavior of real gases.

## 4. How does the Ideal Gas Law relate to the Kinetic Molecular Theory?

The Ideal Gas Law is based on the Kinetic Molecular Theory, which states that gases are composed of particles that are in constant, random motion. The Ideal Gas Law uses this theory to explain the relationship between the pressure, volume, temperature, and number of moles of a gas.

## 5. What is the significance of the Ideal Gas Law in chemistry?

The Ideal Gas Law is a fundamental equation in chemistry that is used to calculate the properties of gases. It is essential in understanding the behavior of gases and is used in various chemical processes, such as the production of industrial gases, gas laws experiments, and gas storage and transportation. It also helps in the study of thermodynamics and the ideal behavior of gases under different conditions.

• Other Physics Topics
Replies
4
Views
1K
• Materials and Chemical Engineering
Replies
1
Views
897
• Mechanical Engineering
Replies
3
Views
1K
• Thermodynamics
Replies
60
Views
4K
• Other Physics Topics
Replies
1
Views
3K
• Introductory Physics Homework Help
Replies
5
Views
745
• Classical Physics
Replies
14
Views
1K
• Other Physics Topics
Replies
9
Views
3K
• Thermodynamics
Replies
22
Views
3K
• Introductory Physics Homework Help
Replies
3
Views
9K