http://www.ck12.org Chapter 2. Matter
pressure of the gas. This relationship between temperature and pressure of a gas is calledAmontons’ law. It was
first proposed by a French scientist named Guillaume Amontons in the late 1600s. Amontons’ gas law is just one of
three commonly known gas laws. The other two are Boyle’s law and Charles’ law.
Q:How does Amontons’ gas law explain the difference in air pressure in Lawrence’s tire?
A:The tire—and the air inside it—got warmer because of friction with the road. The volume of air inside the tire
was more-or-less constant, so the pressure of the air increased when it got warmer.
Particle Pressure
Why does the pressure of a gas increase as it gets warmer? Particles of a gas are constantly moving and bumping
into things. The force of the collisions is measured by pressure. Pressure is the amount of force exerted on a given
area, such as pounds of force per square inch. When gas particles heat up and gain energy, they move faster. This
causes more collisions and greater pressure. Therefore, heating particles of gas in a closed space causes the pressure
of the gas to increase. Explore the behavior of gas particles at different temperatures at the following URL. Change
the temperature of the gas and watch what happens to its particles.
http://www.chm.davidson.edu/vce/kineticmoleculartheory/PT.html
Q:Look at the graph in the simulation above as you change the temperature of the gas. What happens to the pressure
of the gas as its temperature increases?
A:In the graph, the pressure of the gas increases as its temperature increases.
Summary
- According to Amontons’ law, increasing the temperature of a gas while holding its volume constant increases
the pressure of the gas. - When gas particles heat up and gain energy, they move faster. This increases their collisions with each other
and their container, causing greater pressure.
Vocabulary
- Amontons’ law: Gas law stating that, if the volume of a gas is held constant, increasing the temperature of
the gas increases its pressure.
Explore More
Watch the following simple demonstration, and then answer the questions below.
http://www.youtube.com/watch?v=gFDS3bwAU-s (1:57)
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/54898- In this demonstration, when is the pressure of air inside the can greatest? Why?
- How is the volume of air inside the can kept constant after the can is heated?