Use this simple device to experimentally verify the Boyle’s law relationship between the pressure and volume of a gas and the Charles’s law relationship between temperature and volume.
- Boyle’s law—pressure/volume gaseous relationship
- Charles’s law—temperature/volume gaseous relationship
Materials Included In Kit
Syringe with plunger
Syringe tip cap
Wooden base with large (23-mm diameter) predrilled hole
Wooden top with medium (20-mm diameter) predrilled hole
Additional Materials Required
(for each group)
Beaker tongs, insulated gloves or hot vessel gripping device
Ice (to fill the beaker)
Uniform masses (books or other heavy objects of equal weight), 5–8
- Remove the syringe tip cap from the syringe and take the plunger out of the syringe.
- Locate the wooden top piece (it has a medium, 20-mm diameter hole) and set it on a flat surface with the hole upward.
- Press the top end of the plunger firmly into the hole in the wooden top.
- Replace the syringe onto the plunger, set the plunger to the desired volume of air (maximum volume = 30 cc), and then replace the syringe tip cap on the syringe.
- Locate the wooden base piece (it has a larger, 23-mm diameter hole) and set it on a flat surface with the hole facing upward.
- Press the syringe/plunger/wooden top setup into the hole in the wooden base.
- Before beginning the experiment, test the assembled apparatus by pressing down on the wooden top piece. Release the pressure and read the air volume as indicated on the scale of the syringe. If the air volume does not return to close to 30 cc when released, then remove the syringe from the base, remove the tip cap, and draw more air into the cylinder. Recap the end and replace the syringe onto the base. The entire side wall of the black rubber plunger may need to be lubricated with silicone grease or petroleum jelly.
Part 1. Boyle’s Law
Part 2. Charles’s Law
- Gather several (5–8) objects of approximately equal or uniform mass. These may be copies of the same textbook or other heavy objects of equal weight.
- Prepare a data table to record the volume of air in the syringe versus the number of masses added to the apparatus. Note: Create enough columns to record three trials, plus a column for the average volume.
- Before beginning, record the first data point by reading the initial volume of air in the syringe with no masses on the apparatus.
- Stack the first mass on the top block of the apparatus and record the volume of air (in cc) as indicated on the scale of the syringe.
- Continue stacking masses on top of the apparatus, recording the air volume each time.
- After all of the masses are stacked on the apparatus, unstack them one at a time and record the volumes again. Use this data as trial 2.
- Repeat the entire procedure (steps 3–6) if time allows to get two more trials. Average the volume data and record in the data table.
- Plot the data on a sheet of graph paper. Plot the number of masses (which is directly proportional to pressure) on the independent x-axis and the average volume of air on the dependent y-axis.
- Heat 300–350 mL of water in a 400-mL beaker to near-boiling. (Note: The water level must be high enough to cover the portion of the syringe that holds the trapped volume of air.) Use beaker tongs, insulated gloves or a hot vessel gripping device to handle the beaker during the experiment.
- Remove the wooden blocks from the syringe setup used in Part 1.
- Draw 20 cc of air into the syringe and place the tip cap onto the syringe.
- Prepare a data table to record the volume of air in the syringe versus the water temperature (in °C). Note: Create three columns for volume —“Volume In” for the reading after pressing the plunger in, “Volume Out” for the reading after pulling the plunger out, and “Average Volume” for the average.
- Using a thermometer, measure and record the water temperature in the data table. The temperature should be near boiling (90–100 °C).
- Hold the syringe by its top and place the portion of the syringe containing the trapped volume of air under the near-boiling water. Wait a minute or so for the air in the cylinder to reach equilibrium and read the volume of air shown on the syringe scale. Note: To obtain a more accurate volume reading, first quickly push the plunger down into the cylinder and release it. Record this volume as “Volume In.” Next sharply pull the plunger outward and release it. Record the larger volume as “Volume Out.” Average these two measurements to give the “Average Volume,” which helps to correct for some of the friction between the plunger and the wall of the cylinder.
- Use a few ice cubes to bring the water temperature down to ~50 °C. Repeat steps 5 and 6.
- Use ice to lower the water temperature down to ~25 °C (room temperature). Repeat steps 5 and 6.
- Use ice to lower the water temperature down to near 0 °C. Repeat steps 5 and 6.
- Plot the data on a separate sheet of graph paper. Plot the temperature on the independent x-axis and the average volume of air on the dependent y-axis.
If the 30-cc syringe with plunger needs to be replaced, a standard syringe may be purchased and the top plastic rim of the plunger cut off so it fits into the wooden block.
- In the Boyle’s law experiment, a good hyperbola curve can be obtained with as few as four data points; however, more points will provide students with a better curve.
- The Boyle’s law experiment as written uses the number of books to represent the pressure since the two are proportional. An extension to this would be to have students expand their data tables as follows:
Column 1 = number of books
Column 2 = volume of air in cc
Column 3 = mass of books in kilograms
Column 4 = force of books in Newtons (where force = weight = mass x gravity = mass x 9.8 m/sec2)
Column 5 = pressure of books in Newtons/cm2 (where pressure = force/area where the “area” is the area of the syringe opening.
- Use: area = πr2, r = 10.3 mm, area = 333 mm2 or 3.33 cm2) Students may then plot pressure versus volume (column 5 versus column 2).
- The Charles’s law experiment will provide a qualitative view of the temperature–volume relationship. The volume of air in the syringe does not vary greatly over the temperature range from 0 to 100 °C. Expect small volume variations from about 18 cc to 25 cc.
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering Practices
Using mathematics and computational thinking
Analyzing and interpreting data
Developing and using models
Obtaining, evaluation, and communicating information
Disciplinary Core Ideas
MS-PS1.A: Structure and Properties of Matter
MS-PS3.A: Definitions of Energy
HS-PS3.A: Definitions of Energy
HS-PS1.A: Structure and Properties of Matter
Energy and matter
Cause and effect
Systems and system models
Scale, proportion, and quantity
MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
MS-PS1-4: Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
MS-PS3-4: Plan an investigation to determine the relationships among the energy transferred, the type of matter, the mass, and the change in the average kinetic energy of the particles as measured by the temperature of the sample.
HS-PS3-2: Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motion of particles (objects) and energy associated with the relative position of particles (objects).
HS-PS3-4: Plan and conduct an investigation to provide evidence that the transfer of thermal energy when two components of different temperature are combined within a closed system results in a more uniform energy distribution among the components in the system (second law of thermodynamics).
Answers to Questions
- The volume of air decreased as the number of books increased.
- The graph is a downward curve, called a hyperbola.
- An inverse relationship exists between pressure and volume.
- See the Discussion and Tips sections.
- The volume of air decreased as the temperature decreased.
- The graph is a straight line.
- A direct or linear relationship exists between temperature and volume.
The kinetic molecular theory describes the particles in a gas as being far apart and in rapid, random motion. To study the properties of gases, measurements of three macroscopic variables of a given quantity of gas are needed—volume, temperature and pressure.
In 1660, Robert Boyle, a British scientist, performed an experiment that measured the volume of a trapped gas as the pressure on the gas changed, with temperature being held constant. He observed that when the temperature and the number of moles of a sample of gas are held constant, its volume is inversely (or indirectly) proportional to the pressure applied. This is known as Boyle’s law. Volume (V) decreases with increasing pressure (P). Mathematically, this inverse proportionality may be expressed as
P • V = k (where k is a constant),
or alternatively as P1
, where P1
are the initial pressure and volume of the gas and P2
are the final pressure and volume. A plot of V versus P forms a curve called a hyperbola (see Figure 1), showing that the volume doubles as the pressure is halved. Rearranging the equation to give V = k
(1/P) and constructing a plot of V versus 1/P (see Figure 2), a straight line is observed with a slope equal to the constant k
After Boyle’s findings, scientists continued to study the properties of gases. In 1787, Jacques Charles, a French physicist, performed experiments measuring the effect of temperature on the volume of a fixed amount of gas (at constant pressure). He observed that when the pressure and amount of a gas are held constant, the volume of the gas is directly (or linearly) proportional to its temperature. This is known as Charles’s law. Volume increases with increasing temperature. Mathematically, this direct proportionality may be expressed as
or alternatively as V1
(where T is in Kelvin and Kelvin = degrees Celsius + 273). A plot of V versus T is a straight line (see Figure 3), showing that the volume doubles as the temperature (in Kelvin) doubles.
Herron, J. D.; Sarquis, J. L.; Schrader, C. L.; Frank, D. V.; Sarquis, M.; Kukla, D. A. Chemistry; D. C. Heath: Lexington, MA, 1996; pp 205–215.
Zumdahl, S. S. Chemistry, 3rd ed.; D. C. Heath: Lexington, MA, 1993; pp 187–190.