9.2.5

Boyle's Law & Charles' Law

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Investigation of Boyle's Law

Boyle’s Law describes the relationship between the pressure and volume of a fixed mass of gas at constant temperature.

Manometer method

Manometer method

  • Use a pump to change the air pressure on one side of the manometer.
  • Use a pressure gauge on the pump side to measure air pressure, which is equal to the pressure of the air in the glass tube.
  • You can measure the volume of trapped air.
  • Record the volume for several different pressure values.
Analysis of manometer method

Analysis of manometer method

  • If you plot a graph of volume against pressure, you get a monotonically decreasing curve.
  • Plot a graph of V-1 against P and the best fit straight line goes through the origin.
  • This verifies that V-1 is directly proportional to the pressure, i.e. pV is a constant or that P and V are inversely proportional to each other. This assumes that the temperature and mass of the gas is constant.
Further analysis of manometer method

Further analysis of manometer method

  • You can use a logarithmic plot.
    • Plot log(V) against log (P). It doesn’t matter what base logarithm you use.
    • The gradient of the line of best fit should be -1.
  • Assume V = k/P where k is a constant.
    • log(V) = log(k) - log(P).
    • log(V) = - log(P) + log(k).
Further analysis of manometer method 2

Further analysis of manometer method 2

  • Compare the last line with y = mx + c.
  • If log(V) is plotted on the y-axis, with log(P) on the x-axis, the gradient = -1 and the y-intercept should be log(k).
  • You can find the constant, k, using k = Zc, where Z is the base of the logarithms (i.e. 10 or e) and c is the y-intercept.

Investigation of Boyle's Law 2

Boyle’s Law describes the relationship between the pressure and volume of a fixed mass of gas at constant temperature.

Syringe and data logging method

Syringe and data logging method

  • Connect the open end of a syringe to a pressure sensor (which is then connected to data logger and computer).
  • Start recording on data logger.
  • Move the plunger in steps, i.e. decrease or increase the volume of trapped gas slowly so as not to warm or cool the gas.
  • For each new volume, record the pressure.
Syringe and data logging method 2

Syringe and data logging method 2

  • Use software, such as a spreadsheet, to plot a graph of volume against pressure to get a monotonically decreasing curve.
  • Use software to plot a graph of V-1 against P.
  • The best fit straight line should go through the origin, verifying that V-1 is directly proportional to P.
    • i.e. PV = constant or that P and V are inversely proportional to each other, assuming that the temperature and mass of the gas is constant.

Investigation of Charles’ Law

Charles’ Law describes the relationship between the volume and absolute temperature of a fixed mass of gas at constant pressure.

Apparatus

Apparatus

  • Set up the apparatus as shown in the diagram.
  • Caution: it is common practice to use a kerosene-based oil, which needed a separate risk assessment because it is available via CLEAPPS.
Method

Method

  • Keep stirring the water so as to reduce temperature gradients through the water.
  • The length of the air column is directly proportional to the volume of trapped air. This assumes that the inner diameter of the capillary tube is constant.
Analysis

Analysis

  • Plot a graph of the length of air column against temperature on a graph with axes as shown in the diagram.
    • I.e. extended back to -400 °C so that an extrapolation back to the temperature axis can give a value for absolute zero.
  • Notice that the values of volume and temperature are all bunched to the right.
Analysis 2

Analysis 2

  • The extrapolation is suspect because you have to extrapolate a long way before the line hits the temperature axis.
  • Repeating this with different gases, different volumes of gas and at different pressures gives different straight lines. All of the best fit straight lines should pass through the same point on the temperature axis.
Plot the graph again

Plot the graph again

  • If you plot the graph again using the student’s value for absolute zero, the length-temperature graph becomes a straight line through the origin as shown.
  • This shows that the volume of gas is directly proportional to the temperature in Kelvin. This assumes that the pressure and mass of the gas are constant.
Jump to other topics
1

Physical Quantities & Units

1.1

Physical Quantities & Units

1.1.1Use of SI Units1.1.2SI Prefixes, Standard Form & Converting Units1.1.3End of Topic Test - Units & Prefixes1.1.4Avogadro's Constant1.1.5Scalars & Vectors
1.2

Errors & Uncertainty

1.2.1Measuring Length, Time & Volume1.2.2Measuring Temperature1.2.3Circuit Measurements1.2.4Limitation of Physical Measurements1.2.5Uncertainty1.2.6Estimation1.2.7Displaying Data1.2.8End of Topic Test - Measurements & Errors
2

Kinematics

2.1

Equations of Motion

2.1.1Motion in a Straight Line2.1.2Graphs of Motion2.1.3Bouncing Ball Example2.1.4End of Topic Test - Motion in a Straight Line2.1.5Acceleration Due to Gravity
3

Dynamics

3.1

Momentum & Newton's Laws of Motion

3.1.1Mass & Inertia3.1.2Newton's Laws3.1.3Momentum3.1.4End of Topic Test - Newton's Laws & Momentum3.1.5A-A* (AO3/4) - Newton's Third Law
3.2

Non-Uniform Motion

3.2.1Projectile Motion
3.3

Linear Momentum & Conservation

3.3.1Conservation of Momentum
4

Force, Density & Pressure

4.1

Force, Density & Pressure

4.1.1Fields4.1.2Force in Uniform Fields4.1.3Friction4.1.4Buoyancy4.1.5Terminal Speed4.1.6End of Topic Test - Acceleration Due to Gravity4.1.7Centre of Mass4.1.8Forces & Equilibrium4.1.9End of Topic Test - Scalars & Vectors4.1.10Moments4.1.11End of Topic Test - Moments & Centre of Mass4.1.12Density4.1.13Pressure
5

Work, Energy & Power

5.1

Work, Energy & Power

5.1.1Work & Energy5.1.2Power & Efficiency5.1.3Conservation of Energy5.1.4End of Topic Test - Work, Energy & Power
5.2

Gravitational Fields

5.2.1Newton's Law5.2.2Gravitational Field Strength5.2.3Gravitational Potential
6

Deformation of Solids

6.1

Materials

6.1.1Bulk Properties of Solids6.1.2Energy in Materials6.1.3Young Modulus6.1.4End of Topic Test - Materials
7

Waves

7.1

Simple Harmonic Motion

7.1.1Simple Harmonic Motion7.1.2Simple Harmonic Systems7.1.3Energy in Simple Harmonic Motion7.1.4Resonance7.1.5End of Topic Test - Simple Harmonic Motion7.1.6A-A* (AO3/4) - Simple Harmonic Motion7.1.7End of Topic Test - Gravitational Fields
7.2

Waves

7.2.1Progressive Waves7.2.2Intensity of Waves7.2.3Wave Speed & Phase Difference7.2.4Longitudinal & Transverse Waves7.2.5End of Topic Test - Progressive Waves7.2.6Electromagnetic Waves7.2.7Doppler Effect7.2.8Sound Waves7.2.9Measuring Sound Waves7.2.10End of Topic Test - Waves7.2.11Ultrasound Imaging7.2.12Ultrasound Imaging 2
8

Superposition

8.1

Superposition

8.1.1Stationary Waves8.1.2Stationary Waves 28.1.3End of Topic Test - Stationary Waves8.1.4A-A* (AO3/4) - Stationary Waves8.1.5Interference8.1.6Interference 28.1.7End of Topic Test - Interference8.1.8Diffraction8.1.9Diffraction Gratings8.1.10End of Topic Test - Diffraction
9

Thermal Physics

9.1

Circular Motion

9.1.1Circular Motion9.1.2Circular Motion 29.1.3End of Topic Test - Circular Motion
9.2

Thermal Physics

9.2.1Temperature9.2.2Measuring Temperature9.2.3Ideal Gas Law9.2.4Ideal Gases9.2.5Boyle's Law & Charles' Law9.2.6Molecular Kinetic Theory Model9.2.7Molecular Kinetic Theory Model 29.2.8Thermal Energy Transfer9.2.9Thermal Energy Transfer Experiments9.2.10End of Topic Test - Thermal Energy & Ideal Gases9.2.11First Law of Thermodynamics
10

Communication

10.1

Communication Channels

10.1.1Communication Channels10.1.2Modulation10.1.3Attenuation
10.2

Digital Communication

10.2.1Digital & Analogue Signals10.2.2Representing Sound
11

Electric Fields

11.1

Electric Fields

11.1.1Coulomb's Law11.1.2Electric Field Strength11.1.3Electric Field Strength 211.1.4Electric Potential11.1.5End of Topic Test - Electric Fields11.1.6A-A* (AO3/4) - Electric and Gravitational Field
11.2

Capacitance

11.2.1Capacitance11.2.2Parallel Plate Capacitor11.2.3Energy Stored by a Capacitor11.2.4Capacitor Discharge11.2.5Capacitor Charge
12

Current Electricity

12.1

Current Electricity

12.1.1Basics of Electricity12.1.2Mean Drift Velocity12.1.3Current-Voltage Characteristics12.1.4End of Topic Test - Basics of Electricity12.1.5Resistivity12.1.6End of Topic Test - Resistivity & Superconductors12.1.7Power and Conservation12.1.8Microphones12.1.9Components12.1.10Relays12.1.11Strain Gauges
12.2

DC Circuits

12.2.1Circuits12.2.2Potential Divider12.2.3Emf & Internal Resistance12.2.4End of Topic Test - Power & Potential
13

Magnetic Fields

13.1

Magnetic Fields

13.1.1Magnetic Flux Density13.1.2End of Topic Test - Capacitance & Flux Density13.1.3Moving Charges in a Magnetic Field13.1.4Magnetic Flux & Flux Linkage13.1.5Electromagnetic Induction13.1.6Electromagnetic Induction 213.1.7Magnetic Flux Density13.1.8Magnetic Resonance Scanning
13.2

Alternating Currents

13.2.1Alternating Currents13.2.2Operation of a Transformer13.2.3End of Topic Test - Electromagnetic Induction & AC13.2.4Rectification
14

Modern Physics

14.1

Quantum Physics

14.1.1The Photoelectric Effect14.1.2The Photoelectric Effect Explanation14.1.3End of Topic Test - The Photoelectric Effect14.1.4Collisions of Electrons with Atoms14.1.5Energy Levels & Photon Emission14.1.6Wave-Particle Duality14.1.7End of Topic Test - Absorption & Emission14.1.8Band Theory14.1.9Diagnostic X-Rays14.1.10X-Ray Image Processing14.1.11Absorption of X-Rays14.1.12CT Scanners
14.2

Nuclear Physics

14.2.1Rutherford Scattering14.2.2Atomic Model14.2.3Isotopes14.2.4Stable & Unstable Nuclei14.2.5A-A* (AO3/4) - Stable & Unstable Nuclei14.2.6Alpha & Beta Radiation14.2.7Gamma Radiation14.2.8Particles, Antiparticles & Photons14.2.9Quarks & Antiquarks14.2.10Particle Interactions14.2.11Radioactive Decay14.2.12Half Life14.2.13End of Topic Test - Radioactivity14.2.14Nuclear Instability14.2.15Mass & Energy14.2.16Binding Energy14.2.17A-A* (AO3/4) - Nuclear Fusion

Practice questions on Boyle's Law & Charles' Law

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    How are the pressure and volume of a gas related? Multiple choice
  2. 2
    Investigation of Boyle's LawPut in order
  3. 3
    What should the gradient of a log(V) against log (P) graph be?Multiple choice
  4. 4
    Why is it advisable to use a data logger?Multiple choice
  5. 5
    Which of these statements are true about investigating Boyle's law?True / false
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Ideal Gases

Molecular Kinetic Theory Model