# How fast do it take a gas kinetic energy to react to intense heat? [closed]

Let's say I have argon gas in a small container. And opened the flap of the container and stuck a rode that was around 2000-3000 Degrees Fahrenheit, And was only in there for a millisecond. How long will it take the heat to transfer to the gas raising the kinetic energy, causing extreme pressure? Let's also add the gas was frozen to around -5 F. I need to know how fast it take to change the kinetic energy of a gas. And how to make it happen as fast as possible?

P.S Would the heat spread evenly in that short of time frame?

## 1 Answer

I think you are mistaken - while the rod is placed in the container, it will heat up the air via a process known as convection. According to wikipedia, the rate of convection is given by $\frac{dQ}{dt}= hA(T_a-T_b)$ where $\frac{dQ}{dt}$ is the rate of heat transfer, h is a constant for the material, A is the exposed surface area, $T_a$ is the surface temperature of the object, and $T_b$ is the temperature of the gas around the material. My guess is that even at those temperatures, one millisecond will not be enough for the increase in pressure to be as extreme as you are looking for, as the gas around the rod will quickly heat up, but this heat will take a relatively long time to diffuse. As the air around the rod heats up, the rate of heat flow from the rod to the environment will slow down, meaning that only a small amount of the gas in your container will have heated up to a significant temperature.

When you remove the rod, no new energy enters the system. In other words, the average kinetic energy of the gas is now at its maximum. All that will happen is that the energy will become more uniformly distributed, following the second law of thermodynamics. In fact, if you were to get some sort of extreme pressure effect, it would most likely occur very shortly after the rod is removed. At this point, there are a lot of individual high energy particles in the air, which could create a pressure wave, even though the average energy of the particles has not substantially increased. It would quickly be dampened by lower energy particles in the gas, but the velocity of such a wave could be approximated with root-mean-square speed for a gas.

In general, you are correct that the fastest way to change the temperature of a gas is to make it really cold (please note that that a frozen gas is a solid, not a gas. I assume that you just meant that the gas was really cold.) and the inserted object really hot; however, in addition to this, you can make the process even faster by increasing the surface area of your hot object.