http://www.ck12.org Chapter 2. Matter
http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/gaslaw/charles_law.html
Q:What does the graph of the data look like?
A:The graph is a straight line that rises from left to right. This type of graph shows that both variables increase
together at a constant rate.
Q:Could you use the graph to find the volume of a gas at a temperature you didn’t choose for your data table?
A:Yes, you could. You could find the temperature on the temperature scale, trace straight up from this point to the
graph line, and then trace straight across to the volume scale to find the volume for that temperature.
Amazing Motion
Can you guess why the volume of a gas increases when it is heated? Heating a gas gives its particles more energy.
With more energy, the particles move faster. You can see this in the simulation at the URL below. Drag the bar to
increase the temperature, and you’ll be amazed at how fast the particles zigzag around inside the box! If the speedy
particles had more room, they would spread out and the volume of the gas would increase. http://www.colorado.
edu/UCB/AcademicAffairs/ArtsSciences/physics/PhysicsInitiative/Physics2000/bec/temperature.html
Q:Now that you know how a gas behaves when it is heated, can you explain how hot air causes a balloon to inflate?
A:As the air heats, its particles spread out and occupy more space, causing the balloon to inflate.
Summary
- According to Charles’ law, when the pressure of a gas is held constant, increasing its temperature increases its
volume. - Heating a gas gives its particles more energy so they move faster. If the speedy particles have room to spread
out, the volume of the gas will increase.
Vocabulary
- Charles’ law: Gas law stating that, if the pressure of a gas is held constant, increasing its temperature increases
its volume.
Explore More
Do the activity on Charles’ law at the following URL. Be sure to answer the questions at the end of the activity.
http://www.wisc-online.com/objects/ViewObject.aspx?ID=HYP4107
Review
- State how increasing the temperature of a gas changes its volume, assuming pressure is held constant.
- With the help of his dad, a boy blew up a bunch of balloons outside on a hot, sunny day. The outdoor
temperature was 26°C. Then the boy took the balloons inside his air-conditioned house, where the temperature
was 20°C. What do you think happened to the balloons after they had been inside the cool house for a while?
Explain.