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Edexcel A Level (IAL) Physics-5.7 Core Practical 14: Investigating Gas Pressure & Volume- Study Notes- New Syllabus

Edexcel A Level (IAL) Physics -5.7 Core Practical 14: Investigating Gas Pressure & Volume- Study Notes- New syllabus

Edexcel A Level (IAL) Physics -5.7 Core Practical 14: Investigating Gas Pressure & Volume- Study Notes -Edexcel A level Physics – per latest Syllabus.

Key Concepts:

  • CORE PRACTICAL 14: Investigate the relationship between pressure and volume of a gas at fixed temperature

Edexcel A level Physics-Study Notes- All Topics

CORE PRACTICAL 14: Investigate the Relationship Between Pressure and Volume of a Gas at Fixed Temperature

This experiment investigates how the pressure of a gas changes with its volume when the temperature is kept constant. This relationship is known as Boyle’s law.

Aim

To investigate the relationship between pressure and volume of a fixed mass of gas at constant temperature.

Theory (Boyle’s Law)

For a fixed mass of gas at constant temperature:

\( pV = \text{constant} \)

This means:

  • Pressure is inversely proportional to volume
  • As volume decreases, pressure increases
  • As volume increases, pressure decreases

In terms of the ideal gas equation:

\( pV = NkT \)

If \( N \) and \( T \) are constant, then \( pV \) is constant.

Apparatus

  • Gas syringe with scale
  • Pressure sensor or pressure gauge
  • Data logger or digital display
  • Connecting tubing
  • Clamp stand

Method

  1. Connect the gas syringe to the pressure sensor using airtight tubing.
  2. Set an initial volume of gas in the syringe.
  3. Record the corresponding pressure.
  4. Decrease the volume in small steps by pushing the syringe plunger.
  5. At each volume, record the pressure.
  6. Wait briefly at each step to ensure temperature remains constant.
  7. Repeat readings to improve reliability.

Keeping Temperature Constant

  • Change the volume slowly.
  • Allow time for gas to return to room temperature after compression.
  • Avoid rapid compression which increases temperature.

Analysis

  • Plot a graph of pressure \( p \) against volume \( V \).
  • The graph will be a curve showing inverse proportionality.
  • Plot a graph of pressure \( \dfrac{1}{p} \) against \(V \).
  • This graph should be a straight line through the origin.

Conclusion: The experiment confirms that \( p \propto \dfrac{1}{V} \) at constant temperature.

Sources of Error

  • Leaks in tubing or syringe
  • Temperature changes during compression
  • Friction in syringe plunger
  • Calibration error in pressure sensor

Improvements

  • Use a digital pressure sensor with data logging
  • Take readings while increasing and decreasing volume
  • Average repeated readings
  • Allow longer time between measurements

Example

A gas has pressure \( 1.0\times10^{5}\,\mathrm{Pa} \) at volume \( 40\,\mathrm{cm^3} \). Calculate the pressure when the volume is reduced to \( 20\,\mathrm{cm^3} \) at constant temperature.

▶️ Answer / Explanation

Using \( p_1 V_1 = p_2 V_2 \):

\( (1.0\times10^{5})(40) = p_2 (20) \)

\( p_2 = \dfrac{(1.0\times10^{5})(40)}{20} = 2.0\times10^{5}\,\mathrm{Pa} \)

Pressure doubles when volume halves.

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