Skip to Content Go to sign in Skip to Primary Navigation Skip to Secondary Navigation Skip to Page Navigation Skip to Header Navigation Skip to Footer Navigation Read more about accessability options and our navigation

Physics Classroom is making strides to make our site accessible to everyone. Our site contains 6 navigation areas. The Primary, Secondary, and Page Level navigations have a screen reader version of their nav structure that allows using the left and right keys to navigate sibling navigation items, and up or down keys to navigate parent or child navigation items. The others can be navigated using tabs. The Primary Navigation handles the first 2 levels of site pages. The Secondary (which is not always available) handles the 3rd and 4th level of structure. The Page level navigation allows you to navigate the current page's headings quickly. The Header Navigation contains the Light/Dark Mode toggle, Search, Notifications and account login. The Breadcrumb Navigation contains the breadcrumb of the current page. If the current page has a breadcrumb, you can get to it by skipping to the content and tabbing in reverse (shift plus tab). The Footer Navigation contains links such as Privacy, Contact, about and terms. Some resources contain an Audio Player that can be activated by holding down the T key for 3 seconds, and then using K to pause and resume. While not every area of Physics Classroom is usable purely from keyboard and screen reader, we are committed to continue work on making this possible. If you have questions or need additional help, please use this link to contact us.

Return to screen reader navigation
Home Concept Builders Gases and Gas Laws Pressure Concepts Help Help 4

Pressure Concepts - Questions 4 Help

A sample of gas has a pressure due to the collisions of moving gas particles with the container walls. This pressure can be understood at the particle level. Each collision of a gas particle with the container wall results in a force on the wall. Because there are so many particles colliding so frequently with the container wall, there is enough force that accumulates to result in a noticeable pressure. Any variable that effects the ratio of the cumulative amount of force per unit of wall area will effect this pressure.

There are two very similar versions of questions in this Question Group. One of the versions is shown below.
 

Version 1:
Container A is larger than Container B. It's volume and surface are noticeably greater. Both containers are filled with the same number of particles of gas. The type of gas in the two containers are the same. And the speed with which the particles move (on average) is the same for both containers. Which container will have the greatest gas pressure?

Gases push! They push outward upon the walls of the container that contains them. And this pushing is the result of collisions. Each collision of a gas particle on a container wall contributes to an overall amount of force on the wall. By definition, the pressure is the total force divided by the area of the container walls. So to maximize pressure, this ratio of force per area would have to be maximized. The larger the ratio ... the larger the pressure.

So exactly how can this ratio of force per area be maximized. Of the two components of the pressure ratio, the area is easiest to explain. Making the area as small as possible makes the pressure as large as possible.

The force component of this ratio is more difficult to explain. But to keep it simple, the pressure is maximized if the overall and total forcefulness of the collisions of gas particles with container walls is increased. The forcefulness of the collisions can be increased by collisions that ...
 
  • occur at greater speeds.
  • involve more massive particles (assuming the same or greater speed).
  • involve more particles doing the colliding rather than less particles.
  • occur more frequently (either because there are more particles or the particle speed is faster and they can traverse the distance from wall to wall in less time).

In this question, all variables (particle speed, mass of particles, and number of particles) are the same for the two containers with the exception of the container wall area. The pressure will be greater for smaller container wall areas.
Concept Builder Teacher Notes Directions