# Thermal coefficient of expansion in gases

• Vittorio
In summary, the variation in a gas' volume is equal to ΔV = γ⋅V[initial]⋅ΔΘ with ΔΘ the variation in temperature and γ=1/237 the thermal coefficient of expansion in gases. The value of γ=1/237 is derived from the ideal gas law and can be determined by extrapolating experiments on gases. This value corresponds to a temperature of -273 Celsius and is used as the basis for the absolute temperature scale. Additionally, an ideal gas is one in which there are no chemical reactions between the molecules.
Vittorio
I know that the variation in a gas' volume is equal to ΔV = γ⋅V[initial]⋅ΔΘ with ΔΘ the variation in temperature and γ=1/237 the thermal coefficient of expansion in gases. Could someone please explain to me why γ=1/237 please ?
Thanks a lot,
V

Never seen this before. Do you have a source?

Vittorio said:
I know that the variation in a gas' volume is equal to ΔV = γ⋅V[initial]⋅ΔΘ with ΔΘ the variation in temperature and γ=1/237 the thermal coefficient of expansion in gases. Could someone please explain to me why γ=1/237 please ?
Thanks a lot,
V
From the ideal gas law, what is the derivative of volume with respect to temperature at constant pressure? (Are you sure about that 237, or should it be 273?)

Yes, sorry, I meant 273. My phycs teacher told me this, but I hadn't quite understood. Thanks a lot.

Vittorio said:
Yes, sorry, I meant 273. My phycs teacher told me this, but I hadn't quite understood. Thanks a lot.
What about my other question?

I haven't learned about derivatives yet.

Vittorio said:
I haven't learned about derivatives yet.
Are you familiar with the ideal gas law?

I think - a perfect gas is a gas in which there are no chemical reactions between the molecules. I'm not sure, I'm just starting to learn about gases and expansion etc.

For your background it may be more useful to read about the experimental side of the thermal expansion. The 273 value can be determined by extrapolating experiments on gases, as described in section 17.4 of the link below:

http://www.farmingdale.edu/faculty/peter-nolan/pdf/UPCh17.pdf

If you plot the volume versus temperature at constant pressure, you get a straight line which will correspond to zero volume for a temperature of about -273 Celsisus.
The nice thing is that this extrapolated temperature is about the same for all gases (exactly the same for ideal gases, of course). So this led to the definition of an "absolute" temperature scale.

Vittorio said:
I think - a perfect gas is a gas in which there are no chemical reactions between the molecules. I'm not sure, I'm just starting to learn about gases and expansion etc.
Google "Ideal Gas Law"

## What is the thermal coefficient of expansion in gases?

The thermal coefficient of expansion in gases is a measure of how much a gas will expand or contract when its temperature changes. It is represented by the symbol α and is typically measured in units of inverse temperature (1/K).

## How is the thermal coefficient of expansion in gases calculated?

The thermal coefficient of expansion in gases can be calculated by taking the change in volume of a gas divided by the original volume and the change in temperature. This can be expressed mathematically as α = (ΔV/V) / ΔT.

## What factors can affect the thermal coefficient of expansion in gases?

The thermal coefficient of expansion in gases can be affected by several factors, including the type of gas, its pressure, and the temperature range in which it is being measured. In general, gases with larger molecular weights tend to have smaller thermal coefficients of expansion.

## Why is the thermal coefficient of expansion in gases important?

The thermal coefficient of expansion in gases is important in many scientific and industrial applications, as it can affect the accuracy and precision of measurements and the performance of materials and equipment. It is also a key factor in understanding the behavior of gases under different conditions.

## How does the thermal coefficient of expansion in gases compare to that of solids and liquids?

The thermal coefficient of expansion in gases is typically much larger than that of solids and liquids, as gases are more easily compressed and have more space between their molecules. This means that gases tend to expand or contract significantly more with changes in temperature compared to solids and liquids.

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