Pressure and Temperature in Gases

• The volume of gases changes when temperature or pressure vary.
• A hot air balloon increases in size as the air inside of it warms up and expands.
• This is because a gas’s volume expands as its temperature rises.
• Squeezing a container containing gas results in an increase in pressure as the volume decreases.
• This is how a bicycle pump works.
• You may inflate a tyre by compressing the bicycle pump to a high pressure.
• One can sense the force of the intense pressure if you put the tip of your finger on the tip of the pump.

Gases and Kinetic Theory

• Gaseous atoms move continuously and randomly.
• When gaseous particles strike the inside walls of a closed container, pressure is created inside the enclosure.
• Each particle’s kinetic energy increases with temperature as the heat energy is converted to kinetic energy, causing it to travel more quickly.
• The gas’s particles move more quickly as the temperature rises, more frequently striking the container’s walls.
• The container will expand continuously, just like a hot air balloon, if the walls are elastic and pliable.
• If the vessel is made smaller, the frequency of gaseous particles striking the wall increases.
• Thus, a reduction in volume results in an increase in gas pressure.

Diffusion

• Due to the random mobility of their particles, this is the process through which various gases or liquids combine.
• Diffusing particles or atoms which diffuse move in the direction of high concentration to the low concentration area.
• Particles eventually equalize in concentration as they disperse to fill up all of the available space.
• Diffusion occurs naturally without the need for energy input, albeit it happens more quickly at higher temperatures.

Diffusion and Molecular Mass

• Due to the rapid movement of gaseous particles compared to those in liquids, diffusion occurs significantly more quickly in gases than in liquids.
• While the temperature remains uniform, distinct gases do not diffuse at an equal rate.
• This results from the variation in their respective molecular masses.
• A gas will diffuse more quickly the lower its relative mass because lighter gas particles can go farther and faster.
• This can be seen in action in a long glass tube when ammonia, NH₃, and hydrogen chloride gas, HCl, react.
• Ammonium chloride (NH₄Cl), a white smoke, is created when the two gases come together.
• As one might anticipate, this happens much closer to the end of the tube with the hydrogen chloride (Mr = 36.5) and ammonia (Mr = 17) molecules being both smaller and lighter

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