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Gas Laws
A little bit of math to start things out. Lest say you are studying something that has two
properties A and B. A and B could be unrelated to each other and that would be boring. A and
B could be related to each other in some complicated way and that would be a headache. A and
B could be directly proportional to each other; meaning if A doubles B doubles. A fourth choice
is that A is inversely proportional to B; meaning if A doubles B is reduced by half.
Directly
Inversely
A↑ B↑
A↑ B↓
A∝B
A ∝ 1/B
A/B = k
AxB=k
Part 1: (for part 1 only use Model 1 (last page), do not use the book, notes or web). You may;
however, use the simulation at: http://phet.colorado.edu/en/simulation/gas-properties for all
parts.
1) If temperature goes up what happens to volume?
2) Write an equation that relates initial temperature and volume (T1 and V1) to final
temperature and volume (T2 and V2) assuming nothing else changes. (Hint 1: the SI unit
of temperature is the Kelvin. K = 273.15 +° C) (Hint 2: set initial equal to final)
3) If balloon A was heated to 100°C what would its volume be, assuming it did not pop?
4) If pressure goes up what happens to volume?
5) Write an equation that relates initial pressure and volume (P1 and V1) to final pressure
and volume (P2 and V2) assuming nothing else changes.
6) If a SCUBA diver took balloon A to a depth of 15 m where the pressure is 2.5 atm what
would the volume of balloon A be?
7) If temperature goes up what happens to pressure?
8) Write an equation that relates initial temperature and pressure (T1 and P1) to final
temperature and pressure (T2 and P2) assuming nothing else changes.
9) If balloon A was covered in concrete so the balloon’s volume could not change and then
heated to 100°C what would the pressure inside balloon A be?
10) If the number of moles of the gas goes up what happens to pressure?
11) Write an equation that relates initial number of moles of the gas and pressure (n1 and P1)
to final number of moles of the gas and pressure (n2 and P2) assuming nothing else
changes.
12) If balloon A was covered in concrete so the balloon’s volume could not change and then
half of the gas extracted what would the pressure inside balloon A be?
13) If the number of moles of the gas goes up what happens to volume?
14) Write an equation that relates initial number of moles of the gas and volume (n1 and V1)
to final number of moles of the gas and volume (n2 and V2) assuming nothing else
changes.
15) If 0.5 mol of N2 was added to balloon A what would its new volume be, assuming it did
not pop?
16) Write an equation that relates the initial number of moles of the gas, volume, temperature
and pressure (n1, V1, T1 and P1) to the final number of moles of the gas, volume,
temperature and pressure (n2, V2, T2 and P2).
17) Write an equation that relates the number of moles of the gas, volume, temperature and
pressure (n, V, T and P). Hint instead of setting initial equal to final set the variables
equal to a constant R.
18) Solve for the numerical value of R, include units.
19) What would the numerical value of R be if you used mmHg instead of atm for your unit
of pressure?
(760 mmHg = 1atm)
Part 2: (you may use your book, notes, the web and other sources)
20) The above equations are the known as Gas Laws. Use your text find the name for each
equation.
21) You only need to know one of the above equations to know all of them. Which one and
why?
22) What is the pressure in balloon G?
23) How many moles of SF6 are in balloon I?
In what ways did your group work together the best?
In what ways did your group work together the worst? Did you find any bugs or typos in today’s activity? How would you make today’s activity better? What was the most useful thing you learned during this session?
What questions remain uppermost in your mind as we end this session?